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.)
Tested on arch64-linux-gnu. OK for trunk and 6.x?
Thanks,
Richard
libstdc++-v3/
2017-03-10 George Lander <george.lan...@arm.com>
* acinclude.m4 (glibcxx_cv_obsolete_isnan): Define
_GLIBCXX_INCLUDE_NEXT_C_HEADERS before including math.h.
* configure: Regenerate.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index d9859aa..5998fe6 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -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;
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 9bb9862..29456c4 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -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 {
