[Clang][Headers] Fix tgmath.h incompatibility with Glibc #161301
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When building Glibc with Clang, several conformance and math tests related to <tgmath.h> fail. This is because Clang's built-in <tgmath.h> is used by default, which is not fully compatible with the expectations of the Glibc test suite. Glibc provides its own <tgmath.h> which is specifically designed to work with its library implementation, supporting all necessary GNU extensions and features. This patch modifies Clang's <tgmath.h> to detect when it is being used in a Glibc environment (by checking for the `__GLIBC__` macro). When `__GLIBC__` is defined, Clang's header will use `include_next` to include Glibc's system header, effectively deferring to Glibc's implementation. This is the same mechanism already used for macOS (`__APPLE__`). This change allows Glibc to be successfully built and tested with Clang, resolving the following test failures: - conform/ISO11/tgmath.h/conform - conform/ISO99/tgmath.h/conform - conform/POSIX2008/tgmath.h/conform - conform/XOPEN2K/tgmath.h/conform - conform/XOPEN2K8/tgmath.h/conform - math/test-tgmath - math/test-tgmath2 This approach addresses the compatibility issue at its source within Clang, rather than requiring workarounds in Glibc.
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-backend-x86 Author: Zhao Mao (ac-bcc) ChangesWhen building Glibc with Clang, several conformance and math tests related to <tgmath.h> fail. This is because Clang's built-in <tgmath.h> is used by default, which is not fully compatible with the expectations of the Glibc test suite. Glibc provides its own <tgmath.h> which is specifically designed to work with its library implementation, supporting all necessary GNU extensions and features. This patch modifies Clang's <tgmath.h> to detect when it is being used in a Glibc environment (by checking for the This change allows Glibc to be successfully built and tested with Clang, resolving the following test failures:
This approach addresses the compatibility issue at its source within Clang, rather than requiring workarounds in Glibc. Full diff: https://github.com/llvm/llvm-project/pull/161301.diff 1 Files Affected:
diff --git a/clang/lib/Headers/tgmath.h b/clang/lib/Headers/tgmath.h
index 7acf18b9dd357..e79e84b1c72e5 100644
--- a/clang/lib/Headers/tgmath.h
+++ b/clang/lib/Headers/tgmath.h
@@ -17,7 +17,7 @@
* platforms. This is done after #include <math.h> to avoid depcycle conflicts
* between libcxx and darwin in C++ modules builds.
*/
-#if defined(__APPLE__) && __STDC_HOSTED__ && __has_include_next(<tgmath.h>)
+#if (defined(__APPLE__) && __STDC_HOSTED__ && __has_include_next(<tgmath.h>)) || defined(__GLIBC__)
# include_next <tgmath.h>
#else
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You can test this locally with the following command:git-clang-format --diff origin/main HEAD --extensions h -- clang/lib/Headers/tgmath.h
View the diff from clang-format here.diff --git a/clang/lib/Headers/tgmath.h b/clang/lib/Headers/tgmath.h
index e79e84b1c..594e44d55 100644
--- a/clang/lib/Headers/tgmath.h
+++ b/clang/lib/Headers/tgmath.h
@@ -17,7 +17,8 @@
* platforms. This is done after #include <math.h> to avoid depcycle conflicts
* between libcxx and darwin in C++ modules builds.
*/
-#if (defined(__APPLE__) && __STDC_HOSTED__ && __has_include_next(<tgmath.h>)) || defined(__GLIBC__)
+#if (defined(__APPLE__) && __STDC_HOSTED__ && \
+ __has_include_next(<tgmath.h>)) || defined(__GLIBC__)
# include_next <tgmath.h>
#else
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When building Glibc with Clang, several conformance and math tests related to <tgmath.h> fail. This is because Clang's built-in <tgmath.h> is used by default, which is not fully compatible with the expectations of the Glibc test suite.
Glibc provides its own <tgmath.h> which is specifically designed to work with its library implementation, supporting all necessary GNU extensions and features.
This patch modifies Clang's <tgmath.h> to detect when it is being used in a Glibc environment (by checking for the
__GLIBC__macro). When__GLIBC__is defined, Clang's header will useinclude_nextto include Glibc's system header, effectively deferring to Glibc's implementation. This is the same mechanism already used for macOS (__APPLE__).This change allows Glibc to be successfully built and tested with Clang, resolving the following test failures:
This approach addresses the compatibility issue at its source within Clang, rather than requiring workarounds in Glibc.