Mercurial > hg > octave-lojdl > gnulib-hg
changeset 16321:1031e29cf9ff
stdalign: relax _Alignof and tighten _Alignas test
* m4/stdalign.m4 (gl_STDALIGN_H): Relax the _Alignof test,
as it was too strict: alignof must divide offsetof, but it need
not equal offsetof. Inspired by Joseph S. Myers's comment
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023#c10>.
Conversely, tighten the _Alignas test a bit, as the resulting
alignment must be exactly 8.
author | Paul Eggert <eggert@cs.ucla.edu> |
---|---|
date | Fri, 27 Jan 2012 22:17:42 -0800 |
parents | fb33caa0a0ce |
children | 7256be967b3a |
files | ChangeLog m4/stdalign.m4 |
diffstat | 2 files changed, 14 insertions(+), 3 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2012-01-27 Paul Eggert <eggert@cs.ucla.edu> + + stdalign: relax _Alignof and tighten _Alignas test + * m4/stdalign.m4 (gl_STDALIGN_H): Relax the _Alignof test, + as it was too strict: alignof must divide offsetof, but it need + not equal offsetof. Inspired by Joseph S. Myers's comment + <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023#c10>. + Conversely, tighten the _Alignas test a bit, as the resulting + alignment must be exactly 8. + 2012-01-27 Bruno Haible <bruno@clisp.org> stdalign: Document the last change.
--- a/m4/stdalign.m4 +++ b/m4/stdalign.m4 @@ -25,15 +25,16 @@ #else # define ao(type) offsetof (struct { char a; type b; }, b) #endif - char test1[_Alignof (double) == ao (double) ? 1 : -1]; - char test2[alignof (long int) == ao (long int) ? 1 : -1]; + char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1]; + char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1]; + char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1]; /* Test _Alignas only on platforms where gnulib can help. */ #if \ (__GNUC__ || __IBMC__ || __IBMCPP__ \ || 0x5110 <= __SUNPRO_C || 1300 <= _MSC_VER) int alignas (8) alignas_int = 1; - char test3[8 <= _Alignof (alignas_int) ? 1 : -1]; + char test_alignas[_Alignof (alignas_int) == 8 ? 1 : -1]; #endif ]])], [gl_cv_header_working_stdalign_h=yes],