[wasm] Emit webcil payloadSize/tableSize into boot config for streaming instantiation

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17

[pavelsavara]

Split from #129634

Summary

The WASM loader previously instantiated each webcil-in-wasm assembly by buffering its bytes and calling the module's getWebcilSize/getWebcilPayload exports to discover the payload size at runtime. This records the payload size — and, for ReadyToRun images, the indirect-call table size — in the boot config so the loader can stream-instantiate the module directly.

Changes

• Boot config (BootJsonData): a new WebcilAsset : GeneralAsset type carries optional payloadSize (emitted for every webcil-in-wasm assembly) and tableSize (R2R images only). The assembly / coreAssembly / lazyAssembly / satellite asset lists use this type; both fields use EmitDefaultValue = false, so non-webcil assets are unchanged. Only emitted for net11.0+.
• Size reader: WebcilReader.TryReadWebcilInWasmSizes reads payloadSize (+ tableSize for R2R) from data segment 0 of the produced webcil, reusing the existing WasmModuleReader. Covered by unit tests (WebcilInWasmSizesTests).
• Build tasks: a dedicated AttachWebcilSizes task reads the sizes from the already-produced webcil files and attaches them as PayloadSize/TableSize metadata on the resource items. New _AttachBuildWebcilSizes / _AttachPublishWebcilSizes targets run on every boot-config generation (cheap: only the small size header is read), so the metadata is present even on incremental builds where the convert task was skipped for unchanged assemblies. GenerateWasmBootJson consumes the metadata directly and errors if it is missing — there is no file-reading fallback and ConvertDllsToWebcil no longer computes sizes.
• Loader / host (host/assets.ts, loader/assets.ts): instantiateWebcilModule takes payloadSize/tableSize and uses WebAssembly.instantiateStreaming when possible, with no byte buffering and no data-section parsing. Instantiation is wrapped so the payload buffer is freed on failure. For R2R images it wires the host ABI handshake (stack pointer, exception tag, indirect-call table + base, image base) and grows the table before instantiation.

Notes

• payloadSize is emitted for all webcil-in-wasm assemblies; tableSize only appears once ReadyToRun webcil-in-wasm images are produced (separate follow-up work — R2RWebcilPath is consumed here but produced by that work).
• Public loader API surface adds an optional WebcilAsset type (payloadSize/tableSize) in public-api.ts.

Note

This pull request description was generated with the assistance of GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR threads Webcil-in-wasm payload sizing (and future R2R table sizing) from the build pipeline into the generated boot config, then updates the JS loader/host to use those sizes to instantiate WebAssembly modules without buffering and data-section parsing.

Changes:

• Extend boot config assets to optionally include payloadSize (all webcil-in-wasm) and tableSize (R2R-only), and plumb these values through boot config generation.
• Teach the ConvertDllsToWebcil task to compute sizes by parsing the produced wasm and emit them as an MSBuild output; add a GenerateWasmBootJson fallback that re-reads sizes from disk when the convert task is skipped incrementally.
• Update the JS host/loader to pass sizes into instantiateWebcilModule and prefer streaming instantiation when the response MIME type allows it.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs	Collects Webcil sizes (task output or fallback re-read) and passes them into asset emission.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Computes payloadSize/tableSize by parsing produced wasm and exposes them via a new MSBuild output.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonData.cs	Adds optional payloadSize / tableSize fields to the emitted asset shape.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/BootJsonBuilderHelper.cs	Maps computed sizes onto emitted GeneralAsset entries (including culture-qualified satellites).
src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js	Preserves additional wasm exports needed for the R2R host ABI handshake.
src/native/libs/Common/JavaScript/types/public-api.ts	Adds a public WebcilAsset type documenting payloadSize/tableSize.
src/native/libs/Common/JavaScript/types/internal.ts	Extends internal asset entries to carry payloadSize/tableSize through loader pipelines.
src/native/libs/Common/JavaScript/types/ems-ambient.ts	Extends ambient emscripten typings for additional preserved wasm exports.
src/native/libs/Common/JavaScript/loader/assets.ts	Passes tableSize/payloadSize from assets into the host instantiation call.
src/native/libs/Common/JavaScript/host/assets.ts	Implements size-aware (streaming when possible) Webcil module instantiation and R2R import wiring.
src/mono/sample/wasm/Directory.Build.targets	Includes PublishReadyToRun in nested sample build propagation.
src/mono/sample/wasm/Directory.Build.props	Flows nested PublishReadyToRun into the outer build property when unset.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Wires the new WebcilSizes task output into boot config generation for build and publish.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:214

• RecordWebcilSize logs an error when TryReadWebcilSizes fails, but it currently records (and later emits) payloadSize/tableSize even when the parsed payloadSize is 0/negative or tableSize is negative (e.g., due to a malformed/corrupt .wasm or uint32->int overflow). Since payloadSize is required for every webcil-in-wasm assembly, validate the parsed sizes here and fail fast with an actionable error before emitting WebcilSizes metadata.

 if (!TryReadWebcilSizes(webcilPath, out int payloadSize, out int tableSize, out string failureReason))
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{webcilPath}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return;
}

src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets:1005

• _WasmWebcilSizes is populated both during build (_ConvertBuildDllsToWebcil) and again during publish. Because WebcilSizes ItemSpec keys are only culture/filename, a publish invocation that skips ConvertDllsToWebcil can accidentally reuse build-time sizes (preventing GenerateWasmBootJson’s fallback from re-reading the actual publish output). Clear the item group (or split build vs publish item names) before the publish ConvertDllsToWebcil call to avoid cross-phase collisions.

 <ConvertDllsToWebcil Candidates="@(_NewWasmPublishStaticWebAssets)" IntermediateOutputPath="$(_WasmPublishTmpWebcilPath)" OutputPath="$(_WasmPublishWebcilPath)" IsEnabled="$(_WasmEnableWebcil)" WebcilVersion="$(_WasmWebcilVersion)">
<Output TaskParameter="WebcilCandidates" ItemName="_NewWebcilPublishStaticWebAssetsCandidates" />
<Output TaskParameter="FileWrites" ItemName="FileWrites" />
<Output TaskParameter="WebcilSizes" ItemName="_WasmWebcilSizes" />
</ConvertDllsToWebcil>

src/native/libs/Common/JavaScript/host/assets.ts:73

• instantiateWebcilModule now duplicates instantiateWasm’s streaming/ArrayBuffer fallback logic, but it no longer uses instantiateWasm’s error handling (notably the catch that calls dotnetApi.exit(1, err)). That changes failure behavior for Webcil module instantiation and also duplicates the Content-Type check logic in a slightly different way. Reuse instantiateWasm here so Webcil instantiation follows the same streaming heuristics and fatal-error handling as other module loads.

 let instance: WebAssembly.Instance;
const contentType = res.headers && res.headers.get ? res.headers.get("Content-Type") : undefined;
const streamingOk = hasInstantiateStreaming && typeof globalThis.Response === "function" && res instanceof globalThis.Response && contentType === "application/wasm";
if (streamingOk) {
const instantiated = await WebAssembly.instantiateStreaming(res, imports);

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/GenerateWasmBootJson.cs:444

• GenerateWasmBootJson now has new behavior that must remain correct under incremental rebuilds: when ConvertDllsToWebcil is skipped, it falls back to reading payloadSize/tableSize directly from the produced webcil .wasm files to avoid emitting a boot config that the loader can’t consume. There are existing Wasm.Build.Tests that validate incremental boot-json regeneration; extending them to assert that payloadSize (and, when available, tableSize) is still present after a property-only rebuild would help prevent regressions in this critical incremental path.

 // Fast path: ConvertDllsToWebcil already computed the sizes. Fall back to
// reading them straight from the produced webcil when it didn't: that task is
// incremental and can be skipped while this boot config is regenerated (e.g. a
// boot-config property changed but no assembly did), which would otherwise drop
// payloadSize/tableSize and break the loader. R2R images especially need
// tableSize before instantiation.

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

Suppressed comments (4)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:537

• PayloadSize/TableSize are read as u32 but cast directly to int. If the high bit is set this will wrap to a negative value and TryReadWebcilInWasmSizes will return true, leaving callers to fail later (often with an empty failureReason). It should validate the u32 values are in range (and non-zero for payloadSize) and return false with a FailureReason when they are not.

 PayloadSize = (int)ReadUInt32LE(sizes, 0);
TableSize = want == 8 ? (int)ReadUInt32LE(sizes, 4) : 0;
HasSizes = true;

src/native/libs/Common/JavaScript/host/assets.ts:56

• payloadSize/tableSize come from boot config; currently only payloadSize===0 is rejected and a negative/non-integer value would flow into posix_memalign/table.grow, potentially throwing or allocating incorrectly. This can also be triggered by u32→int overflow on the producer side. Validate both values are finite integers and enforce payloadSize>0 and tableSize>=0.

 if (typeof payloadSize !== "number" || payloadSize === 0) {
throw new Error(`Webcil asset '${virtualPath}' is missing payloadSize in the boot config.`);
}
const tableEntries = typeof tableSize === "number" ? tableSize : 0;

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs:149

• Log message has an extra space before the period after the source path, which makes logs look sloppy and harder to search/compare.

 Log.LogMessage(MessageImportance.Low, $"Staged prebuilt R2R webcil {finalWebcil} from {r2rWebcilPath} .");

src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/AttachWebcilSizes.cs:48

• If TryReadWebcilInWasmSizes returns true but payloadSize is <= 0 (or if failureReason comes back null), the logged error message will include an empty reason: "(... )". Capture the ok flag separately and provide a fallback reason so failures are actionable.

 if (!WebcilReader.TryReadWebcilInWasmSizes(path, out int payloadSize, out int tableSize, out string failureReason) || payloadSize <= 0)
{
Log.LogError($"Could not read the Webcil payload/table sizes from '{path}' ({failureReason}). The runtime loader requires payloadSize for every webcil-in-wasm assembly.");
return false;
}

[maraf]

Looks good to me 👍

[pavelsavara]

/ba-g just timeout, but green tests

https://helix.dot.net/api/jobs/1c48125e-cfbb-459e-ba96-7a1dec6b0819/workitems?api-version=2019-06-17