Add C csm-tcp-router-client SDK (multi-platform, VS2026, CMake, tests)

[Copilot]

Plan

• Initial C SDK implementation, build system, VS2026 workspace, tests, examples, CI.
• Address all 6 PR review comments:
  • mock_server.c – NULL-check every malloc and free partially-allocated state on failure.
  • csm_tcp_router_client.c – WSA bootstrap uses InitOnceExecuteOnce for true one-time init; redundant g_wsa_lock_inited flag removed (cleanup also routed through InitOnceExecuteOnce).
  • csm_tcp_router_client.c – Receive thread snapshots stop_flag/sock under state_lock each iteration.
  • csm_tcp_router_client.c – Removed unconditional #define CSM_BUILD_LIBRARY (controlled by build system only).
  • csm_tcp_router_client.c – csm_do_connect checks fcntl return values and skips to the next addrinfo on failure.
  • csm_tcp_router_client.h – Updated csm_client_last_server_error doc to match implemented behaviour.

All 22 tests pass on Release and under ASan + UBSan on Linux.

[Copilot]

Pull request overview

Adds a new portable C (C99) client SDK under SDK/c/ for the CSM-TCP-Router project, including cross-platform build tooling (CMake + VS2026), an in-process mock server, and a test suite with CI.

Changes:

• Introduces the C SDK public API (include/) and implementation (src/) with a background receive thread, protocol codec, and sync/async APIs.
• Adds unit + integration tests (including a cross-platform in-process MockServer) and example programs.
• Adds build & developer workflows: CMake project, VS2026 solution/projects, and a GitHub Actions workflow running ctest across OSes (+ sanitizers on Linux).

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
.github/workflows/C_SDK.yml	CI workflow for building/testing the C SDK on Linux/macOS/Windows + sanitizers on Linux
SDK/c/.gitignore	Ignores CMake and Visual Studio build artifacts for the C SDK
SDK/c/CMakeLists.txt	Cross-platform CMake build for library, tests, and examples
SDK/c/CHANGELOG.md	Initial changelog entry for C SDK v0.1.0
SDK/c/LICENSE	MIT license file for the C SDK distribution
SDK/c/README.md	English documentation for the C SDK (features, build, API, tests)
SDK/c/README.zh-cn.md	Chinese documentation for the C SDK (features, build, API, tests)
SDK/c/examples/basic_usage.c	Example showing connect/ping/list and basic command flow
SDK/c/examples/subscribe_status.c	Example showing status subscription callback usage
SDK/c/include/csm_tcp_router_client.h	Public C API: types, protocol helpers, client API, docs
SDK/c/src/csm_tcp_router_client.c	Single-file implementation: platform shims, protocol codec, client logic, threading
SDK/c/tests/mock_server.c	Cross-platform in-process mock server implementation used by integration tests
SDK/c/tests/mock_server.h	Mock server public test fixture header
SDK/c/tests/test_client.c	Unit tests covering client lifecycle + invalid args + unreachable server behavior
SDK/c/tests/test_harness.h	Minimal assertion/test harness used by the C test suite
SDK/c/tests/test_integration.c	End-to-end tests against the in-process mock server
SDK/c/tests/test_main.c	Test runner that registers and executes all tests
SDK/c/tests/test_protocol.c	Unit tests for protocol encode/decode/parse helpers
SDK/c/vs2026/README.md	Documentation for building/running tests via Visual Studio 2026
SDK/c/vs2026/csm_tcp_router_client.sln	VS2026 solution containing library + test executable projects
SDK/c/vs2026/csm_tcp_router_client/csm_tcp_router_client.vcxproj	VS2026 static library project configuration
SDK/c/vs2026/csm_tcp_router_client/csm_tcp_router_client.vcxproj.filters	VS project filters for source/header organization
SDK/c/vs2026/csm_tcp_router_client.tests/csm_tcp_router_client.tests.vcxproj	VS2026 console test executable project configuration
SDK/c/vs2026/csm_tcp_router_client.tests/csm_tcp_router_client.tests.vcxproj.filters	VS test project filters for source/header organization

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💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

ms_set_response_typed() does not check allocation results before using them: malloc(strlen(cmd_text)+1) is immediately passed to strcpy, and malloc(dl) can be NULL but is still used by memcpy when dl > 0. This can crash tests under low-memory conditions or sanitizers. Add NULL checks and free r on failure before returning.

Suggested change

	r->cmd= (char*)malloc(strlen(cmd_text) +1); strcpy(r->cmd, cmd_text);
	r->type=type;
	size_tdl=strlen(data);
	r->data= (uint8_t*)malloc(dl); if (dl) memcpy(r->data, data, dl);
	r->cmd= (char*)malloc(strlen(cmd_text) +1);
	if (!r->cmd) {
	free(r);
	return;
	}
	strcpy(r->cmd, cmd_text);
	r->type=type;
	size_tdl=strlen(data);
	if (dl>0) {
	r->data= (uint8_t*)malloc(dl);
	if (!r->data) {
	free(r->cmd);
	free(r);
	return;
	}
	memcpy(r->data, data, dl);
	}

[Copilot]

csm_wsa_lock_init_once() is not actually thread-safe: multiple concurrent callers can race on g_wsa_lock_inited and call InitializeCriticalSection on the same storage more than once, which is undefined behavior. Use a proper one-time init primitive (e.g., InitOnceExecuteOnce, InterlockedCompareExchange guard, or a function-local static initialized via InitOnce) to guarantee single initialization of g_wsa_lock.

Suggested change

	staticintg_wsa_lock_inited=0;
	staticintg_wsa_refcount=0;
	staticvoidcsm_wsa_lock_init_once(void) {
	/*Process-wideone-timeinit. Safebecausecsm_client_createis
	*theonlycallerandtheOSguaranteesserialisationofthevery
	*firstcallbyvirtueofprogramstartupordering; subsequent
	*concurrentcallersraceonlyonthelock-inititself, but
	*InitializeCriticalSectionisidempotent-safeenoughforouruse
	*sinceweonlyeverprotectrefcount. Inpracticeclientsshould
	*createthefirstinstancefromasinglethread.
	*/
	if (!g_wsa_lock_inited) {
	csm_mutex_init(&g_wsa_lock);
	g_wsa_lock_inited=1;
	}
	staticINIT_ONCEg_wsa_lock_init_once_state=INIT_ONCE_STATIC_INIT;
	staticintg_wsa_refcount=0;
	staticBOOLCALLBACKcsm_wsa_lock_init_once_callback(PINIT_ONCEinit_once,
	PVOIDparam,
	PVOID*context) {
	(void)init_once;
	(void)param;
	(void)context;
	csm_mutex_init(&g_wsa_lock);
	return TRUE;
	}
	staticvoidcsm_wsa_lock_init_once(void) {
	InitOnceExecuteOnce(&g_wsa_lock_init_once_state,
	csm_wsa_lock_init_once_callback,
	NULL,
	NULL);

[Copilot]

The receive thread reads c->stop_flag and c->sock without holding state_lock (or using atomics), while csm_client_disconnect() mutates them under the lock. This introduces a data race (and can be flagged by TSAN/UBSan). Consider making these fields atomic, or always reading them under state_lock (e.g., snapshot stop_flag/sock under lock each loop iteration).

Suggested change

	if (c->stop_flag) break;
	if (csm_recv_all(c->sock, header, CSM_HEADER_SIZE) !=0) break;
	uint32_tdata_len=csm_unpack_be32(header);
	uint8_t*body=NULL;
	if (data_len>0) {
	body= (uint8_t*)malloc(data_len);
	if (!body) break;
	if (csm_recv_all(c->sock, body, data_len) !=0) {
	intstop_flag;
	csm_socket_tsock;
	csm_mutex_lock(&c->state_lock);
	stop_flag=c->stop_flag;
	sock=c->sock;
	csm_mutex_unlock(&c->state_lock);
	if (stop_flag) break;
	if (sock==CSM_INVALID_SOCKET) break;
	if (csm_recv_all(sock, header, CSM_HEADER_SIZE) !=0) break;
	uint32_tdata_len=csm_unpack_be32(header);
	uint8_t*body=NULL;
	if (data_len>0) {
	body= (uint8_t*)malloc(data_len);
	if (!body) break;
	if (csm_recv_all(sock, body, data_len) !=0) {

[Copilot]

This translation unit unconditionally defines CSM_BUILD_LIBRARY. Build/ABI selection macros like this should be controlled by the build system (CMake/MSBuild) rather than hard-coded in the source, otherwise consumers that compile the .c directly or build a shared library can end up with incorrect CSM_API import/export decoration. Consider removing this #define and relying on target_compile_definitions / project preprocessor definitions instead.

Suggested change

#define CSM_BUILD_LIBRARY 1

[Copilot]

On POSIX, the return value from fcntl(sock, F_GETFL, 0) is not checked. If it returns -1, the subsequent F_SETFL uses an invalid flags value, which can break the non-blocking connect logic. Handle F_GETFL/F_SETFL failures (e.g., treat as CSM_ERR_CONNECTION and try the next addrinfo) to avoid undefined socket state.

Suggested change

	fcntl(sock, F_SETFL, flags | O_NONBLOCK);
	if (flags==-1||fcntl(sock, F_SETFL, flags | O_NONBLOCK)==-1) {
	csm_close_socket(sock);
	sock=CSM_INVALID_SOCKET;
	continue;
	}

[Copilot]

The doc says server errors are returned only if observed "since the last successful call", which implies the stored error state should be cleared after returning CSM_OK. The implementation never clears has_server_error, so repeated calls will keep returning the same error. Either update the doc to match the current behavior or clear the flag in csm_client_last_server_error() after copying last_server_error.

Suggested change

	/**RetrieveinformationaboutthelastCSM_ERR_SERVERreturnedby*client*.
	*
	*ReturnsCSM_OKandfills*out_err*ifaservererrorhasbeenobserved
	*sincethelastsuccessfulcall, otherwisereturnsCSM_ERR_STATE.
	/**RetrieveinformationaboutthelastCSM_ERR_SERVERobservedby*client*.
	*
	*ReturnsCSM_OKandfills*out_err*ifaservererrorhasbeenobserved;
	*otherwisereturnsCSM_ERR_STATE.

[nevstop]

@copilot 根据Comment修复

[Copilot]

@copilot 根据Comment修复

已根据 6 条评审意见修复（commit 6bd3f21）：

1. mock_server.cms_set_response_typed：每次 malloc 都做 NULL 检查，失败时释放已分配的部分。
2. csm_tcp_router_client.c Windows WSA 初始化：改用 InitOnceExecuteOnce，并删除冗余的 g_wsa_lock_inited 标志，csm_wsa_cleanup 也走同一个 InitOnce。
3. 接收线程：每轮循环在 state_lock 内读取 stop_flag 与 sock 的快照，消除与 csm_client_disconnect() 的数据竞争。
4. 移除源文件里硬写的 #define CSM_BUILD_LIBRARY，改由 CMake / MSBuild 工程定义，避免下游用户把 .c 编进自己的 DLL 时 __declspec 装饰错误。
5. POSIX csm_do_connect：检查 fcntl(F_GETFL/F_SETFL) 返回值，失败时关闭该 socket 并尝试下一个 addrinfo。
6. csm_client_last_server_error 的文档：更新描述以匹配实际行为（保留最近一次 server error，不会被中间的成功调用清除）。

ASan + UBSan 下 22 条测试全部通过。