Thanks, I tried to fix that by pushing the following patch; please give it a try.
I had tested with Clang before, but I was using Clang 2.x and the problem is new to Clang 3.x (which I don't have). It strikes me, though, that this sort of approach cannot work if <stdalign.h> is installed into a directory intended to be used by shared libraries or whatnot. This is because the compiler used in the configure-time test for <stdalign.h> may not be the same as the compiler used later, when the shared library is compiled against. I expect that this isn't the only place where gnulib has this problem, though, and since it's purely theoretical right now for stdalign.h I didn't pursue it. stdalign: port to Clang 3.0 Problem reported by Simon Josefsson in <http://lists.gnu.org/archive/html/bug-gnulib/2011-12/msg00005.html>. * doc/posix-headers/stdalign.texi (stdalign.h): Mention Clang 3.0, which has <stdalign.h> but which does not define alignof. * m4/stdalign.m4 (gl_STDALIGN_H): Check for Clang 3.0's problem. diff --git a/doc/posix-headers/stdalign.texi b/doc/posix-headers/stdalign.texi index b3d39f0..bebc70d 100644 --- a/doc/posix-headers/stdalign.texi +++ b/doc/posix-headers/stdalign.texi @@ -13,6 +13,8 @@ Portability problems fixed by Gnulib: @itemize @item This header file is missing on most circa-2011 platforms. +@item +Clang 3.0's @code{<stdalign.h>} does not define @code{alignof}/@code{_Alignof}. @end itemize Portability problems not fixed by Gnulib: diff --git a/m4/stdalign.m4 b/m4/stdalign.m4 index da64dc6..2641dce 100644 --- a/m4/stdalign.m4 +++ b/m4/stdalign.m4 @@ -9,9 +9,24 @@ dnl with or without modifications, as long as this notice is preserved. AC_DEFUN([gl_STDALIGN_H], [ - AC_CHECK_HEADERS_ONCE([stdalign.h]) + AC_CACHE_CHECK([for working stdalign.h], + [gl_cv_header_working_stdalign_h], + [AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM( + [[#include <stdalign.h> + int align_int = alignof (int) + _Alignof (double); - if test $ac_cv_header_stdalign_h = yes; then + /* 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; + #endif + ]])], + [gl_cv_header_working_stdalign_h=yes], + [gl_cv_header_working_stdalign_h=no])]) + + if test $gl_cv_header_working_stdalign_h = yes; then STDALIGN_H='' else STDALIGN_H='stdalign.h'
