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| author | Jakub Jelinek <jakub@redhat.com> | 2025-01-21 09:14:01 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2025-01-21 09:14:01 +0100 |
| commit | 2a6816883107ee4a4aabb43763ce079512f3f0f8 (patch) | |
| tree | 1ca8b16a1f41cf8dc3553bfe36cc7602c5a23bd6 | |
| parent | 843ca8a964bcfeae72d9d48e2dd549fa818120e3 (diff) | |
| download | gcc-2a6816883107ee4a4aabb43763ce079512f3f0f8.zip gcc-2a6816883107ee4a4aabb43763ce079512f3f0f8.tar.gz gcc-2a6816883107ee4a4aabb43763ce079512f3f0f8.tar.bz2 | |
c, c++: Return 1 for __has_builtin(__builtin_va_arg) and __has_builtin(__builtin_c23_va_start)
The Linux kernel uses its own copy of stdarg.h.
Now, before GCC 15, our stdarg.h had
#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
#define va_start(v, ...) __builtin_va_start(v, 0)
#else
#define va_start(v,l) __builtin_va_start(v,l)
#endif
va_start definition but GCC 15 has:
#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
#define va_start(...) __builtin_c23_va_start(__VA_ARGS__)
#else
#define va_start(v,l) __builtin_va_start(v,l)
#endif
I wanted to suggest to the kernel people during their porting to C23
that they'd better use C23 compatible va_start macro definition,
but to make it portable, I think they really want something like
#if defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L
#define va_start(v, ...) __builtin_va_start(v, 0)
#ifdef __has_builtin
#if __has_builtin(__builtin_c23_va_start)
#undef va_start
#define va_start(...) __builtin_c23_va_start(__VA_ARGS__)
#endif
#else
#define va_start(v,l) __builtin_va_start(v,l)
#endif
or so (or with >= 202311L), as GCC 13-14 and clang don't support
__builtin_c23_va_start (yet?) and one gets better user experience with
that.
Except it seems __has_builtin(__builtin_c23_va_start) doesn't actually work,
it works for most of the stdarg.h __builtin_va_*, doesn't work for
__builtin_va_arg (neither C nor C++) and didn't work for
__builtin_c23_va_start if it was available.
The following patch wires __has_builtin for those.
2025-01-21 Jakub Jelinek <jakub@redhat.com>
gcc/c/
* c-decl.cc (names_builtin_p): Return 1 for RID_C23_VA_START and
RID_VA_ARG.
gcc/cp/
* cp-objcp-common.cc (names_builtin_p): Return 1 for RID_VA_ARG.
gcc/testsuite/
* c-c++-common/cpp/has-builtin-4.c: New test.
| -rw-r--r-- | gcc/c/c-decl.cc | 2 | ||||
| -rw-r--r-- | gcc/cp/cp-objcp-common.cc | 1 | ||||
| -rw-r--r-- | gcc/testsuite/c-c++-common/cpp/has-builtin-4.c | 16 |
3 files changed, 19 insertions, 0 deletions
diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc index 314b118..68d331b 100644 --- a/gcc/c/c-decl.cc +++ b/gcc/c/c-decl.cc @@ -11804,6 +11804,8 @@ names_builtin_p (const char *name) case RID_CHOOSE_EXPR: case RID_OFFSETOF: case RID_TYPES_COMPATIBLE_P: + case RID_C23_VA_START: + case RID_VA_ARG: return 1; default: break; diff --git a/gcc/cp/cp-objcp-common.cc b/gcc/cp/cp-objcp-common.cc index fc6c790..8336d0b 100644 --- a/gcc/cp/cp-objcp-common.cc +++ b/gcc/cp/cp-objcp-common.cc @@ -587,6 +587,7 @@ names_builtin_p (const char *name) case RID_BUILTIN_ASSOC_BARRIER: case RID_BUILTIN_BIT_CAST: case RID_OFFSETOF: + case RID_VA_ARG: return 1; case RID_BUILTIN_OPERATOR_NEW: case RID_BUILTIN_OPERATOR_DELETE: diff --git a/gcc/testsuite/c-c++-common/cpp/has-builtin-4.c b/gcc/testsuite/c-c++-common/cpp/has-builtin-4.c new file mode 100644 index 0000000..65d2b18 --- /dev/null +++ b/gcc/testsuite/c-c++-common/cpp/has-builtin-4.c @@ -0,0 +1,16 @@ +/* { dg-do preprocess } */ + +#if __has_builtin (__builtin_va_start) != 1 +#error "No __builtin_va_start" +#endif +#if __has_builtin (__builtin_va_end) != 1 +#error "No __builtin_va_end" +#endif +#if __has_builtin (__builtin_va_arg) != 1 +#error "no __builtin_va_arg" +#endif +#if __STDC_VERSION__ >= 202311L +#if __has_builtin (__builtin_c23_va_start) != 1 +#error "no __builtin_c23_va_start" +#endif +#endif |