Add Emscripten-specific linker by RReverser · Pull Request #39490 · rust-lang/rust

RReverser · 2017-02-03T16:15:22Z

Emscripten claims to accept most GNU linker options, but in fact most of -Wl,... are useless for it and instead it requires some additional special options which are easier to handle in a separate trait.

Currently added:

export_symbols: works on executables as special Emscripten case since staticlibs/dylibs aren't compiled to JS, while exports are required to be accessible from JS.
FixesConfigure C function exports correctly for emscripten targets #39171.
optimize - translates Rust's optimization level to Emscripten optimization level (whether passed via -C opt-level=... or -O...).
FixesOptimize emscripten targets with emcc #36899.
debuginfo - translates debug info; Emscripten has 5 debug levels while Rust has 3, so chose to translate -C debuginfo=1 to -g3 (preserves whitespace, variable and function names for easy debugging).
FixesEnable source maps when targeting asmjs in debug mode #36901.
no_default_libraries - tells Emscripten to exclude memcpy and co.

TODO (in future PR): dynamic linking via SIDE_MODULE / MAIN_MODULE mechanism.

rust-highfive · 2017-02-03T16:15:38Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nrc (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

RReverser · 2017-02-03T16:20:31Z

r? @brson @alexcrichton

RReverser · 2017-02-03T16:23:28Z

Ah, so this command assigns only one reviewer at a time. This is my first PR, so I might have missed something. I'll be away for the weekend, but please do leave comments if something needs to be changed and I'll fix it as soon as I'm back.

alexcrichton · 2017-02-03T19:12:23Z

This looks great to me, thanks for the PR! I'll leave the final review to @brson though who's our "Emscripten czar"

It looks like there may also be a tidy error on Travis which needs to be fixed?

RReverser · 2017-02-04T01:31:24Z

Indeed, also just noticed a minor whitespace glitch.

RReverser · 2017-02-04T21:51:26Z

Both should be fixed now.

alexcrichton · 2017-02-04T22:41:52Z

@bors: r+

bors · 2017-02-04T22:41:52Z

📌 Commit db2df7d has been approved by alexcrichton

bors · 2017-02-05T16:59:57Z

☔ The latest upstream changes (presumably #39563) made this pull request unmergeable. Please resolve the merge conflicts.

RReverser · 2017-02-06T01:36:38Z

Should I rebase on top of @pepyakin's changes now or wait for @brson's review?

alexcrichton · 2017-02-06T01:47:45Z

Ah if you want to go ahead and rebase I can r+

RReverser · 2017-02-06T01:51:10Z

Done. (TIL Github has conflict resolving UI, is that something new? I don't think I saw it before)

RReverser · 2017-02-06T01:51:53Z

No, wait, it didn't merge cleanly, I'll better repeat later from my laptop.

alexcrichton · 2017-02-06T01:56:58Z

It looks like this is set in two places, maybe a merge conflict gone wrong?

Yeah, as said above. Previous PR had exactly same changes as mine too :(

RReverser · 2017-02-06T02:00:21Z

Should be merging cleanly now.

alexcrichton · 2017-02-06T07:30:22Z

@bors: r+

bors · 2017-02-06T07:30:23Z

📌 Commit 82b5a09 has been approved by alexcrichton

bors · 2017-02-06T13:20:26Z

⌛ Testing commit 82b5a09 with merge 1c193bb...

bors · 2017-02-06T14:10:09Z

💔 Test failed - status-travis

RReverser · 2017-02-06T21:38:20Z

That's something new...

RReverser · 2017-02-07T19:43:32Z

Well emscripten task worked after rebase, so 🤷‍♂️

@alexcrichton @brson Could you please take a look while it's not broken again? :)

alexcrichton · 2017-02-07T19:53:35Z

@bors: r+

alexcrichton · 2017-02-10T02:19:14Z

@bors: r+

bors · 2017-02-10T02:19:15Z

📌 Commit 908ed36 has been approved by alexcrichton

bors · 2017-02-10T03:59:56Z

⌛ Testing commit 908ed36 with merge 912ff3a...

bors · 2017-02-10T04:50:06Z

💔 Test failed - status-travis

RReverser · 2017-02-10T09:17:45Z

@alexcrichton Just to reconfirm - when you did r+ and @bors says "Commit 908ed36 has been approved by alexcrichton" and "Testing commit 908ed36 with merge 912ff3a..." - does it mean that all commits where approved and merged for testing or the previous one (aa83c3e) wasn't? Looks like both, so this is cwd missing in some another place. I'm starting to think that it could be easier to disable that optimization with separate memory file rather than try to deal with it. I'll try one more time though.

alexcrichton · 2017-02-10T15:09:48Z

@RReverser ah yeah looks like you figure out the what-was-tested question I think?

IIRC this is an existing bug (#38454), so it may not be the easiest to work around (although I'm not too privvy to the intricacies of the bug here)

RReverser · 2017-02-10T16:37:14Z

@alexcrichton Oach, I see... Will be harder to workaround if it's on Cargo side indeed. I'll see if I can, if not, I'll just disable that specific optimization for now.

RReverser · 2017-02-10T16:48:06Z

@alexcrichton So there is memoryInitializerPrefixURL which I can set to whatever value needed. It's strange though that Emscripten doesn't default it to __dirname in Node.js environment, in which case issue wouldn't exist in the first place (perhaps worth making PR to them later too).

RReverser · 2017-02-10T17:06:08Z

Ok, I think I'm just going to disable memory file until that issue is resolved. Fixing it in both Rust test runners and Cargo is too cumbersome at the moment.

It claims to accept most GNU linker options, but in fact most of them have no effect and instead it requires some special options which are easier to handle in a separate trait. Currently added: - `export_symbols`: works on executables as special Emscripten case since staticlibs/dylibs aren't compiled to JS, while exports are required to be accessible from JS. Fixesrust-lang#39171. - `optimize` - translates Rust's optimization level to Emscripten optimization level (whether passed via `-C opt-level=...` or `-O...`). Fixesrust-lang#36899. - `debuginfo` - translates debug info; Emscripten has 5 debug levels while Rust has 3, so chose to translate `-C debuginfo=1` to `-g3` (preserves whitespace, variable and function names for easy debugging). Fixesrust-lang#36901. - `no_default_libraries` - tells Emscripten to exlude `memcpy` and co.

It's support is currently too buggy in both Rust tests and Cargo.

RReverser · 2017-02-10T19:04:59Z

Let's hope this was the last issue.

alexcrichton · 2017-02-10T19:20:39Z

@bors: r+

bors · 2017-02-10T19:20:40Z

📌 Commit f35b598 has been approved by alexcrichton

bors · 2017-02-10T23:50:50Z

⌛ Testing commit f35b598 with merge 064a0ee...

Add Emscripten-specific linker Emscripten claims to accept most GNU linker options, but in fact most of `-Wl,...` are useless for it and instead it requires some additional special options which are easier to handle in a separate trait. Currently added: - `export_symbols`: works on executables as special Emscripten case since staticlibs/dylibs aren't compiled to JS, while exports are required to be accessible from JS. Fixes#39171. - `optimize` - translates Rust's optimization level to Emscripten optimization level (whether passed via `-C opt-level=...` or `-O...`). Fixes#36899. - `debuginfo` - translates debug info; Emscripten has 5 debug levels while Rust has 3, so chose to translate `-C debuginfo=1` to `-g3` (preserves whitespace, variable and function names for easy debugging). Fixes#36901. - `no_default_libraries` - tells Emscripten to exclude `memcpy` and co. TODO (in future PR): dynamic linking via `SIDE_MODULE` / `MAIN_MODULE` mechanism.

RReverser · 2017-02-11T00:03:40Z

@alexcrichton Offtop question as I watch Travis logs: is it not configured to cache compiled LLVM between builds? It seems to rebuild it every time, even though LLVM is not updated between most of them.

alexcrichton · 2017-02-11T00:05:58Z

Oh we use sccache to cache LLVM. That means we go through the rigamarole of configure-and-make, but the actual compiles take very little time. Overall an entire LLVM build (cached) should take ~4min

RReverser · 2017-02-11T00:07:42Z

@alexcrichton Ah, I just saw that Travis uploads some artifacts in the end of the build to its own cache (?), so thought LLVM objects could be part of it too?

alexcrichton · 2017-02-11T00:08:13Z

Nah those are just the docker images we use across builds, all of the LLVM files are stored in S3 via sccache

RReverser · 2017-02-11T01:35:37Z

Yessss 🍾 https://travis-ci.org/rust-lang/rust/jobs/200535437

I don't fully like that we had to disable memory init file for now, but that's hopefully just a temporary measure and still better to have 95% of optimizations out of the box than none :)

bors · 2017-02-11T02:29:34Z

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing 064a0ee to master...

alexcrichton · 2017-02-11T02:30:50Z

🌮

Nice!

rust-highfive assigned nrc Feb 3, 2017

rust-highfive assigned brson and unassigned nrc Feb 3, 2017

RReverser force-pushed the em-linker branch from 76c2d61 to db2df7dCompare February 4, 2017 19:54

frewsxcv mentioned this pull request Feb 5, 2017
Rollup of 12 pull requests #39565
Closed

alexcrichton reviewed Feb 6, 2017
View reviewed changes

RReverser force-pushed the em-linker branch from f244cc2 to 82b5a09Compare February 6, 2017 01:59

RReverser force-pushed the em-linker branch from 82b5a09 to 87b8c9eCompare February 7, 2017 19:34

RReverser added 2 commits February 10, 2017 17:31

Reenable exception catching in Emscripten even on optimized targets
84c2a67

RReverser force-pushed the em-linker branch from 908ed36 to 44d9a70Compare February 10, 2017 17:31

Disable memory init file until further notice
f35b598
It's support is currently too buggy in both Rust tests and Cargo.

RReverser force-pushed the em-linker branch from 44d9a70 to f35b598Compare February 10, 2017 17:34

bors merged commit f35b598 into rust-lang:masterFeb 11, 2017

RReverser mentioned this pull request Feb 11, 2017
Search for .mem in same directory as Node script emscripten-core/emscripten#4936
Closed

RReverser mentioned this pull request Apr 19, 2017
Allow linking JS libraries to Emscripten target #41409
Closed

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