NEWS.stable: log cherry-pick [e446f25]->[c092018] relocatable-shell: Update suggested...

[gnulib.git] / m4 / stdalign.m4

diff --git a/m4/stdalign.m4 b/m4/stdalign.m4
index 5c97942..9efafe5 100644 (file)
--- a/m4/stdalign.m4
+++ b/m4/stdalign.m4
@@ -1,6 +1,6 @@
-# Check for stdalign.h that conforms to C1x.
+# Check for stdalign.h that conforms to C11.
 
-dnl Copyright 2011-2012 Free Software Foundation, Inc.
+dnl Copyright 2011-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -14,13 +14,29 @@ AC_DEFUN([gl_STDALIGN_H],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <stdalign.h>
-            int align_int = alignof (int) + _Alignof (double);
+            #include <stddef.h>
+
+            /* Test that alignof yields a result consistent with offsetof.
+               This catches GCC bug 52023
+               <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>.  */
+            #ifdef __cplusplus
+               template <class t> struct alignof_helper { char a; t b; };
+            # define ao(type) offsetof (alignof_helper<type>, b)
+            #else
+            # define ao(type) offsetof (struct { char a; type b; }, b)
+            #endif
+            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__ \
+                ((defined __cplusplus && 201103 <= __cplusplus) \
+                 || __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC \
                  || 0x5110 <= __SUNPRO_C || 1300 <= _MSC_VER)
-              int alignas (8) alignas_int = 1;
+              struct alignas_test { char c; char alignas (8) alignas_8; };
+              char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
+                                ? 1 : -1];
             #endif
           ]])],
        [gl_cv_header_working_stdalign_h=yes],