Use ::isinf and ::isnan if libc defines them

	PR libstdc++/48891
	* acinclude.m4 (GLIBCXX_CHECK_MATH11_PROTO): Check for obsolete isinf
	and isnan functions.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/c_global/cmath (isinf(double), isnan(double))
	[_GLIBCXX_HAVE_OBSOLETE_ISINF_ISNAN]: Import via using-directive.
	* testsuite/26_numerics/headers/cmath/48891.cc: New.

git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@232327 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 48 insertions, 0 deletions

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 94120ec4dd5..38f14f6729e 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -18174,6 +18174,54 @@ fi
       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_math11_overload" >&5
 $as_echo "$glibcxx_cv_math11_overload" >&6; }
       ;;
+    *-*-*gnu*)
+      # If <math.h> defines the obsolete isinf(double) and isnan(double)
+      # functions (instead of or as well as the C99 generic macros) then we
+      # can't define std::isinf(double) and std::isnan(double) in <cmath>
+      # and must use the ones from <math.h> instead.
+      { $as_echo "$as_me:${as_lineno-$LINENO}: checking for obsolete isinf and isnan functions in <math.h>" >&5
+$as_echo_n "checking for obsolete isinf and isnan functions in <math.h>... " >&6; }
+        if test "${glibcxx_cv_obsolete_isinf_isnan+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+
+          cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <math.h>
+             #undef isinf
+             #undef isnan
+             namespace std {
+               using ::isinf;
+               bool isinf(float);
+               bool isinf(long double);
+               using ::isnan;
+               bool isnan(float);
+               bool isnan(long double);
+             }
+             using std::isinf;
+             using std::isnan;
+             bool b = isinf(0.0) || isnan(0.0);
+
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  glibcxx_cv_obsolete_isinf_isnan=yes
+else
+  glibcxx_cv_obsolete_isinf_isnan=no
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+
+
+
+      if test $glibcxx_cv_obsolete_isinf_isnan = yes; then
+
+$as_echo "#define HAVE_OBSOLETE_ISINF_ISNAN 1" >>confdefs.h
+
+      fi
+      { $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_obsolete_isinf_isnan" >&5
+$as_echo "$glibcxx_cv_obsolete_isinf_isnan" >&6; }
+      ;;
   esac
 
   CXXFLAGS="$ac_save_CXXFLAGS"