math: Import isinf and others to global namespace

Starting from C++11, several math functions, like isinf, moved into the std
namespace. Since cmath undefines those functions before redefining them inside
the namespace, and glibc 2.23 defines the C variants as macros, the C variants
in global namespace are not accessible any longer.

v2: Move the fix outside of Nouveau, as suggested by Jose Fonseca, since anyone
    might need it when GCC switches to C++14 by default with GCC 6.0.

v3:
*   Put the code directly inside c99_math.h rather than creating a new header
    file, as asked by Jose Fonseca;
*   Guard the code behind glibc version checks, as only glibc > =2.23 defines
    isinf & co. as functions, as suggested by Jose Fonseca.

Signed-off-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Jose Fonseca <jfonseca@vmware.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/c99_math.h b/include/c99_math.h
index 250e08d..e906c26 100644
--- a/include/c99_math.h
+++ b/include/c99_math.h
@@ -185,4 +185,27 @@ fpclassify(double x)
 #endif
 
 
+/* Since C++11, the following functions are part of the std namespace. Their C
+ * counteparts should still exist in the global namespace, however cmath
+ * undefines those functions, which in glibc 2.23, are defined as macros rather
+ * than functions as in glibc 2.22.
+ */
+#if __cplusplus >= 201103L && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 23))
+#include <cmath>
+
+using std::fpclassify;
+using std::isfinite;
+using std::isinf;
+using std::isnan;
+using std::isnormal;
+using std::signbit;
+using std::isgreater;
+using std::isgreaterequal;
+using std::isless;
+using std::islessequal;
+using std::islessgreater;
+using std::isunordered;
+#endif
+
+
 #endif /* #define _C99_MATH_H_ */