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[libstdc++-v3] Fix detection of obsolete isnan 

libstdc++-v3 configure checks whether old glibc inline definitions
of isnan would conflict with the libstdc++-v3 definitions and
works around them if so.  But if g++ 6.x build A is used to build
another g++ 6.x B, the configure step for B will pick up the math.h
installed alongside A instead of the glibc version.  configure will
then assume that the workaround isn't necessary, leaving B with a
broken cmath.

isinf already worked around this.  This patch extends the same fix
to isnan.  (Thanks to George for the fix.)

libstdc++-v3/
2017-03-10  George Lander  <george.lander@arm.com>

	* acinclude.m4 (glibcxx_cv_obsolete_isnan): Define
	_GLIBCXX_INCLUDE_NEXT_C_HEADERS before including math.h.
	* configure: Regenerate.

From-SVN: r246025
This commit is contained in:
George Lander 2017-03-10 12:22:45 +00:00 committed by Richard Sandiford
parent f1b0632aab
commit 74106ead26
3 changed files with 9 additions and 1 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2017-03-10 George Lander <george.lander@arm.com>
* acinclude.m4 (glibcxx_cv_obsolete_isnan): Define
_GLIBCXX_INCLUDE_NEXT_C_HEADERS before including math.h.
* configure: Regenerate.
2017-03-09 Jonathan Wakely <jwakely@redhat.com>
* include/std/functional (_Not_fn): Define macro to simplify

3
libstdc++-v3/acinclude.m4
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@ -2297,7 +2297,8 @@ AC_DEFUN([GLIBCXX_CHECK_MATH11_PROTO], [
AC_MSG_CHECKING([for obsolete isnan function in <math.h>])
AC_CACHE_VAL(glibcxx_cv_obsolete_isnan, [
AC_COMPILE_IFELSE([AC_LANG_SOURCE(
[#include <math.h>
[#define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
#include <math.h>
#undef isnan
namespace std {
using ::isnan;

1
libstdc++-v3/configure vendored
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@ -18390,6 +18390,7 @@ else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
#include <math.h>
#undef isnan
namespace std {