[bazel] Port #145358: LIBC_THREAD_MODE

[rupprecht]

I'm not sure how libc should be configuring this in bazel, but for now it seems like LIBC_THREAD_MODE_PLATFORM restores the default behavior.

Defining this param is required:

ERROR: /var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/c9d34ded3a9d94cc250207948aceadfc/external/llvm-project/libc/BUILD.bazel:5788:14: Compiling libc/src/stdio/generic/vprintf.cpp failed: (Exit 1): clang failed: error executing CppCompile command (from target @@llvm-project//libc:vprintf) /usr/lib/llvm-18/bin/clang -U_FORTIFY_SOURCE -fstack-protector -Wall -Wthread-safety -Wself-assign -Wunused-but-set-parameter -Wno-free-nonheap-object -fcolor-diagnostics -fno-omit-frame-pointer ... (remaining 31 arguments skipped)
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
In file included from external/llvm-project/libc/src/stdio/generic/vprintf.cpp:11:
In file included from external/llvm-project/libc/src/__support/File/file.h:19:
external/llvm-project/libc/src/__support/threads/mutex.h:25:2: error: LIBC_THREAD_MODE is undefined
   25 | #error LIBC_THREAD_MODE is undefined
      |  ^

As an alternative to this PR, we could make the libc header default to LIBC_THREAD_MODE_PLATFORM if not provided, instead of an #error

[llvmbot]

@llvm/pr-subscribers-libc

Author: Jordan Rupprecht (rupprecht)

Changes

I'm not sure how libc should be configuring this in bazel, but for now it seems like LIBC_THREAD_MODE_PLATFORM restores the default behavior.

Defining this param is required:

ERROR: /var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/c9d34ded3a9d94cc250207948aceadfc/external/llvm-project/libc/BUILD.bazel:5788:14: Compiling libc/src/stdio/generic/vprintf.cpp failed: (Exit 1): clang failed: error executing CppCompile command (from target @@<!-- -->llvm-project//libc:vprintf) /usr/lib/llvm-18/bin/clang -U_FORTIFY_SOURCE -fstack-protector -Wall -Wthread-safety -Wself-assign -Wunused-but-set-parameter -Wno-free-nonheap-object -fcolor-diagnostics -fno-omit-frame-pointer ... (remaining 31 arguments skipped)
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
In file included from external/llvm-project/libc/src/stdio/generic/vprintf.cpp:11:
In file included from external/llvm-project/libc/src/__support/File/file.h:19:
external/llvm-project/libc/src/__support/threads/mutex.h:25:2: error: LIBC_THREAD_MODE is undefined
   25 | #error LIBC_THREAD_MODE is undefined
      |  ^

As an alternative to this PR, we could make the libc header default to LIBC_THREAD_MODE_PLATFORM if not provided, instead of an #error

---

Full diff: https://github.com/llvm/llvm-project/pull/151539.diff

1 Files Affected:

• (modified) utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl (+3)

diff --git a/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl b/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
index 96d7fa86e9ddf..b49e7c3fad954 100644
--- a/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
+++ b/utils/bazel/llvm-project-overlay/libc/libc_configure_options.bzl
@@ -46,4 +46,7 @@ LIBC_CONFIGURE_OPTIONS = [
 
     # Documentation in libc/src/__support/libc_assert.h
     # "LIBC_COPT_USE_C_ASSERT",
+
+    # Documentation in libc/docs/configure.rst
+    "LIBC_THREAD_MODE=LIBC_THREAD_MODE_PLATFORM",
 ]

[saturn691]

Hmm, it should default to LIBC_THREAD_MODE_PLATFORM...

llvm-project/libc/config/config.json

Lines 8 to 13 in 7abb519

	"threads": {
	"LIBC_CONF_THREAD_MODE": {
	"value": "LIBC_THREAD_MODE_PLATFORM",
	"doc": "The implementation used for Mutex, acceptable values are LIBC_THREAD_MODE_PLATFORM, LIBC_THREAD_MODE_SINGLE, and LIBC_THREAD_MODE_EXTERNAL."
	}
	},

[rupprecht]

Hmm, it should default to LIBC_THREAD_MODE_PLATFORM...

AFAICT, the bazel config doesn't read those json files. What I'm suggesting is the header file itself could default, i.e. use this:

#if !defined(LIBC_THREAD_MODE)
#define LIBC_THREAD_MODE LIBC_THREAD_MODE_PLATFORM
#endif // LIBC_THREAD_MODE

Instead of

llvm-project/libc/src/__support/threads/mutex.h

Lines 24 to 26 in 99d70e0

	#if !defined(LIBC_THREAD_MODE)
	#error LIBC_THREAD_MODE is undefined
	#endif // LIBC_THREAD_MODE

I don't have a preference though. Forcing the build system to define the vars is fine w/ me.