[Bug c++/37582] New: std::pow strange overload resolution

[Bug c++/37582] New: std::pow strange overload resolution

[jarausch at igpm dot rwth-aachen dot de]

gcc is complaining about an ambiguous overloading of operator&&
in the statement (last non-trivial line)
    return std::pow(a,2.0);

where no such operator appears. (I haven't seen a macro definition of 'pow'
which pulls in '&&')

If I replace the statement above by
    return ::pow(a,2.0);

the error disappears.

The function 'pow' should be injected into namespace 'std'
when doing
#include <cmath>

or am I missing something?


-- 
           Summary: std::pow strange overload resolution
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jarausch at igpm dot rwth-aachen dot de
 GCC build triplet: i386
  GCC host triplet: i386
GCC target triplet: i386


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] std::pow strange overload resolution

[jarausch at igpm dot rwth-aachen dot de]

------- Comment #1 from jarausch at igpm dot rwth-aachen dot de  2008-09-19 07:33 -------
Created an attachment (id=16360)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16360&action=view)
preprocessed failing source code


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] std::pow strange overload resolution

[jarausch at igpm dot rwth-aachen dot de]

------- Comment #2 from jarausch at igpm dot rwth-aachen dot de  2008-09-19 07:35 -------
gcc -v -save-temps -c TEST3.C
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-4.3.1-r1/work/gcc-4.3.1/configure --prefix=/usr
--bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.3.1
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.3.1
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.3.1/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.3.1/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4
--host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec
--enable-nls --without-included-gettext --with-system-zlib --disable-checking
--disable-werror --enable-secureplt --disable-multilib --enable-libmudflap
--disable-libssp --enable-cld --enable-java-awt=gtk --with-arch=i686
--enable-languages=c,c++,java,treelang,fortran --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.3.1-r1 p1.1'
Thread model: posix
gcc version 4.3.1 (Gentoo 4.3.1-r1 p1.1) 
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-mtune=generic' '-march=i686'
 /usr/libexec/gcc/i686-pc-linux-gnu/4.3.1/cc1plus -E -quiet -v -D_GNU_SOURCE
TEST3.C -mtune=generic -march=i686 -fpch-preprocess -o TEST3.ii
ignoring nonexistent directory
"/usr/lib/gcc/i686-pc-linux-gnu/4.3.1/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4/i686-pc-linux-gnu
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4/backward
 /usr/local/include
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-c' '-mtune=generic' '-march=i686'
 /usr/libexec/gcc/i686-pc-linux-gnu/4.3.1/cc1plus -fpreprocessed TEST3.ii
-quiet -dumpbase TEST3.C -mtune=generic -march=i686 -auxbase TEST3 -version -o
TEST3.s
GNU C++ (Gentoo 4.3.1-r1 p1.1) version 4.3.1 (i686-pc-linux-gnu)
        compiled by GNU C version 4.3.1, GMP version 4.2.3, MPFR version 2.3.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 80bbbbf6aed7cf0c473d383e5ba3eede
TEST3.C: In function 'double S_Precision::square(double)':
TEST3.C:57: error: ISO C++ says that these are ambiguous, even though the worst
conversion for the first is better than the worst conversion for the second:
TEST3.C:57: note: candidate 1: operator&&(bool, bool) <built-in>
TEST3.C:46: note: candidate 2: bool S_Precision::operator&&(int, const
S_Precision::super_real&)
/usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4/cmath:389: error: ISO C++
says that these are ambiguous, even though the worst conversion for the first
is better than the worst conversion for the second:
/usr/lib/gcc/i686-pc-linux-gnu/4.3.1/include/g++-v4/cmath:389: note: candidate
1: operator&&(bool, bool) <built-in>
TEST3.C:46: note: candidate 2: bool S_Precision::operator&&(int, const
S_Precision::super_real&)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-09-19 09:34 -------
Shorter testcase:

#include <cmath>

class super_real {
public:
    super_real (double);
};

bool operator&& (int i, const super_real& a);

double square(double a) {
    return std::pow(a,2.0);
}


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |rejects-valid
      Known to fail|                            |4.3.0 4.3.2
      Known to work|                            |4.2.4 4.4.0
           Priority|P3                          |P1
   Last reconfirmed|0000-00-00 00:00:00         |2008-09-19 09:34:07
               date|                            |
            Summary|std::pow strange overload   |[4.3 Regression] std::pow
                   |resolution                  |strange overload resolution
   Target Milestone|---                         |4.3.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2008-09-22 19:55 -------
Is && part of GNU C++98 now?


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #5 from jakub at gcc dot gnu dot org  2008-10-22 21:22 -------
Couldn't cmath just use:
   template<typename _Tp, typename _Up>
     inline
     typename __gnu_cxx::__promote_2<
-    typename __gnu_cxx::__enable_if<__is_arithmetic<_Tp>::__value
-        && __is_arithmetic<_Up>::__value,
+    typename __gnu_cxx::__enable_if<bool(__is_arithmetic<_Tp>::__value)
+        && bool(__is_arithmetic<_Up>::__value),
         _Tp>::__type, _Up>::__type
     pow(_Tp __x, _Up __y)
     {
...
?  Though 4.4 cc1plus doesn't complain...


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bkoz at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2008-12-11 11:45 -------
Janis, can we have your regression hunting services to look what fixed this
on the mainline?


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |janis at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[hjl dot tools at gmail dot com]

------- Comment #7 from hjl dot tools at gmail dot com  2008-12-11 17:20 -------
It is fixed by revision 133519:

http://gcc.gnu.org/ml/gcc-cvs/2008-03/msg00738.html
http://gcc.gnu.org/ml/gcc-patches/2008-03/msg01285.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug c++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #8 from jakub at gcc dot gnu dot org  2008-12-11 17:25 -------
That looks very invasive for the branch.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #9 from jakub at gcc dot gnu dot org  2008-12-11 19:55 -------
Created an attachment (id=16888)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16888&action=view)
gcc43-pr37582.patch

Given:
  // N.B. The conversions to bool are needed due to the issue
  // explained in c++/19404.
  template<class _Sp, class _Tp>
    struct __traitor
    {
      enum { __value = bool(_Sp::__value) || bool(_Tp::__value) };
      typedef typename __truth_type<__value>::__type __type;
    };
I see this isn't the first time libstdc++ works around the C++ bug.
So, either IMHO we should cast to bool there, or as done in this patch
use __traitor instead.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[paolo dot carlini at oracle dot com]

------- Comment #10 from paolo dot carlini at oracle dot com  2008-12-11 20:04 -------
(In reply to comment #9)
> So, either IMHO we should cast to bool there, or as done in this patch
> use __traitor instead.

For the branch, I pre-approve a patch adding and using __traitand.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #11 from jakub at gcc dot gnu dot org  2008-12-11 20:32 -------
Created an attachment (id=16889)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16889&action=view)
gcc43-pr37582.patch

Thanks for pointing the difference between || and &&, embarrassing.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #16888|0                           |1
        is obsolete|                            |
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #12 from jakub at gcc dot gnu dot org  2008-12-12 08:47 -------
Subject: Bug 37582

Author: jakub
Date: Fri Dec 12 08:46:26 2008
New Revision: 142704

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=142704
Log:
        PR c++/37582
        * include/bits/cpp_type_traits.h (struct __traitand): New.
        * include/c_global/cmath (std::atan2, std::pow): Use __traitand
        instead of && as first argument to __enable_if.
        * include/c_std/cmath (std::atan2): Likewise.
        * testsuite/26_numerics/headers/cmath/37582.cc: New.

Added:
   
branches/gcc-4_3-branch/libstdc++-v3/testsuite/26_numerics/headers/cmath/37582.cc
Modified:
    branches/gcc-4_3-branch/libstdc++-v3/ChangeLog
    branches/gcc-4_3-branch/libstdc++-v3/include/bits/cpp_type_traits.h
    branches/gcc-4_3-branch/libstdc++-v3/include/c_global/cmath
    branches/gcc-4_3-branch/libstdc++-v3/include/c_std/cmath


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #13 from jakub at gcc dot gnu dot org  2008-12-12 08:51 -------
Fixed.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582

[Bug libstdc++/37582] [4.3 Regression] std::pow strange overload resolution

[jakub at gcc dot gnu dot org]

------- Comment #14 from jakub at gcc dot gnu dot org  2008-12-12 11:23 -------
Subject: Bug 37582

Author: jakub
Date: Fri Dec 12 11:22:33 2008
New Revision: 142707

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=142707
Log:
        PR c++/37582
        * testsuite/26_numerics/headers/cmath/37582.cc: New.

Added:
    trunk/libstdc++-v3/testsuite/26_numerics/headers/cmath/37582.cc
Modified:
    trunk/libstdc++-v3/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37582