kern/181501: [regression] libstdc++ vs. std::isfinite() since math.h at r253260

[Jan Beich]

>Number:         181501
>Category:       kern
>Synopsis:       [regression] libstdc++ vs. std::isfinite() since math.h at r253260
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 24 12:40:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Jan Beich
>Release:        FreeBSD 10.0-CURRENT amd64
>Organization:
>Environment:
>Description:
Recent math.h cleanup made c++ inconsistent in how it treats an integer
argument for float functions between different standard libraries.

cf. http://lists.cs.uiuc.edu/pipermail/cfe-dev/2013-January/027280.html

>How-To-Repeat:
$ cat a.cc
#include <cmath>

int main()
{
  std::isfinite(5);

  return 0;
}

$ c++ -stdlib=libc++ a.cc
$ c++ -stdlib=libstdc++ a.cc
In file included from a.cc:1:
/usr/include/c++/4.2/cmath:472:51: error: controlling expression type 'int' not compatible with any generic association type
    __capture_isfinite(_Tp __f) { return isfinite(__f); }
                                                  ^~~
/usr/include/math.h:115:38: note: expanded from macro 'isfinite'
#define isfinite(x) __fp_type_select(x, __isfinitef, __isfinite, __isfinitel)
                                     ^
/usr/include/math.h:86:49: note: expanded from macro '__fp_type_select'
#define __fp_type_select(x, f, d, ld) _Generic((x),                     \
                                                ^
/usr/include/c++/4.2/cmath:543:45: note: in instantiation of function template specialization '__gnu_cxx::__capture_isfinite<int>' requested here
    isfinite(_Tp __f) { return ::__gnu_cxx::__capture_isfinite(__f); }
                                            ^
a.cc:5:8: note: in instantiation of function template specialization 'std::isfinite<int>' requested here
  std::isfinite(5);
       ^
1 error generated.

>Fix:
either !defined(__cplusplus) or !defined(__GLIBCXX__)

--- math.h_cxx.diff begins here ---
Index: lib/msun/src/math.h
===================================================================
--- lib/msun/src/math.h	(revision 254772)
+++ lib/msun/src/math.h	(working copy)
@@ -82,7 +82,7 @@ extern const union __nan_un {
 #define	FP_ZERO		0x10
 
 #if (__STDC_VERSION__ >= 201112L && defined(__clang__)) || \
-    __has_extension(c_generic_selections)
+    __has_extension(c_generic_selections) && !defined(__cplusplus)
 #define	__fp_type_select(x, f, d, ld) _Generic((x),			\
     float: f(x),							\
     double: d(x),							\
--- math.h_cxx.diff ends here ---


>Release-Note:
>Audit-Trail:
>Unformatted: