Mercurial > gnulib
changeset 17950:c617c92c3ad8
stddef: port to pre-C11 GCC on x86
On this platform, max_align_t should have an alignment of 8 even
though the storage alignments of double, long, etc. max out at 4.
Inspired by a comment of Andreas Schwab's here:
https://sourceware.org/ml/libc-alpha/2015-04/msg00017.html
* lib/stddef.in.h (_GL_STDDEF_ALIGNAS) [!HAVE_MAX_ALIGN_T]: New macro.
(max_align_t) [!HAVE_MAX_ALIGN_T]: Use it.
* tests/test-stddef.c: Test __alignof__ too, if available.
| author | Paul Eggert <eggert@cs.ucla.edu> |
|---|---|
| date | Thu, 02 Apr 2015 10:35:53 -0700 |
| parents | b25f1b45e6fd |
| children | 2ae3c246cda5 |
| files | ChangeLog lib/stddef.in.h tests/test-stddef.c |
| diffstat | 3 files changed, 36 insertions(+), 4 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog Tue Mar 24 12:23:28 2015 +0000 +++ b/ChangeLog Thu Apr 02 10:35:53 2015 -0700 @@ -1,3 +1,14 @@ +2015-04-02 Paul Eggert <eggert@cs.ucla.edu> + + stddef: port to pre-C11 GCC on x86 + On this platform, max_align_t should have an alignment of 8 even + though the storage alignments of double, long, etc. max out at 4. + Inspired by a comment of Andreas Schwab's here: + https://sourceware.org/ml/libc-alpha/2015-04/msg00017.html + * lib/stddef.in.h (_GL_STDDEF_ALIGNAS) [!HAVE_MAX_ALIGN_T]: New macro. + (max_align_t) [!HAVE_MAX_ALIGN_T]: Use it. + * tests/test-stddef.c: Test __alignof__ too, if available. + 2015-03-24 Pádraig Brady <P@draigBrady.com> quotearg-simple-tests: add missing gl_FUNC_MMAP_ANON dependency
--- a/lib/stddef.in.h Tue Mar 24 12:23:28 2015 +0000 +++ b/lib/stddef.in.h Thu Apr 02 10:35:53 2015 -0700 @@ -83,12 +83,23 @@ /* Some platforms lack max_align_t. */ #if !@HAVE_MAX_ALIGN_T@ +/* On the x86, the maximum storage alignment of double, long, etc. is 4, + but GCC's C11 ABI for x86 says that max_align_t has an alignment of 8, + and the C11 standard allows this. Work around this problem by + using __alignof__ (which returns 8 for double) rather than _Alignof + (which returns 4), and align each union member accordingly. */ +# ifdef __GNUC__ +# define _GL_STDDEF_ALIGNAS(type) \ + __attribute__ ((__aligned__ (__alignof__ (type)))) +# else +# define _GL_STDDEF_ALIGNAS(type) /* */ +# endif typedef union { - char *__p; - double __d; - long double __ld; - long int __i; + char *__p _GL_STDDEF_ALIGNAS (char *); + double __d _GL_STDDEF_ALIGNAS (double); + long double __ld _GL_STDDEF_ALIGNAS (long double); + long int __i _GL_STDDEF_ALIGNAS (long int); } max_align_t; #endif
--- a/tests/test-stddef.c Tue Mar 24 12:23:28 2015 +0000 +++ b/tests/test-stddef.c Thu Apr 02 10:35:53 2015 -0700 @@ -55,6 +55,16 @@ verify (alignof (size_t) <= alignof (max_align_t)); verify (alignof (wchar_t) <= alignof (max_align_t)); verify (alignof (struct d) <= alignof (max_align_t)); +#if defined __GNUC__ || defined __IBM__ALIGNOF__ +verify (__alignof__ (double) <= __alignof__ (max_align_t)); +verify (__alignof__ (int) <= __alignof__ (max_align_t)); +verify (__alignof__ (long double) <= __alignof__ (max_align_t)); +verify (__alignof__ (long int) <= __alignof__ (max_align_t)); +verify (__alignof__ (ptrdiff_t) <= __alignof__ (max_align_t)); +verify (__alignof__ (size_t) <= __alignof__ (max_align_t)); +verify (__alignof__ (wchar_t) <= __alignof__ (max_align_t)); +verify (__alignof__ (struct d) <= __alignof__ (max_align_t)); +#endif int main (void)