Mercurial > octave
changeset 21446:822dc5a202c9
build: Fix C11 compliance detection to work with clang
* prog_c.m4 (OCTAVE_PROG_CC_C11): Use offsetof macro to provide an
integral constant expression that can be evaluated at compile-time
to work with stricter compilers (e.g. clang).
| author | Mike Miller <mtmiller@octave.org> |
|---|---|
| date | Mon, 14 Mar 2016 13:06:59 -0700 |
| parents | de155ca994d4 |
| children | ac1e50cfc9ed |
| files | m4/prog_c.m4 |
| diffstat | 1 files changed, 7 insertions(+), 1 deletions(-) [+] |
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--- a/m4/prog_c.m4 Sun Mar 13 08:46:59 2016 -0700 +++ b/m4/prog_c.m4 Mon Mar 14 13:06:59 2016 -0700 @@ -32,6 +32,7 @@ AC_DEFUN([OCTAVE_PROG_CC_C11], [_OCTAVE_C_STD_TRY([c11], [_OCTAVE_C_C99_TEST_HEADER[ +#include <stddef.h> // Check _Alignas. char _Alignas (double) aligned_as_double; char _Alignas (0) no_special_alignment; @@ -81,7 +82,12 @@ [_OCTAVE_C_C99_TEST_BODY[ v1.i = 2; v1.w.k = 5; - _Static_assert (&v1.i == &v1.w.k, "Anonymous union alignment botch"); + // FIXME: Octave-specific change, this feature test is modified from the + // original Autoconf source. The address-of operator is not an integral + // constant expression and cannot be used with _Static_assert. + _Static_assert (offsetof(struct anonymous, i) + == offsetof(struct anonymous, w.k), + "Anonymous union alignment botch"); ]], dnl Try dnl GCC -std=gnu11 (unused restrictive mode: -std=c11)