[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-03-29
     Ever Confirmed|0                           |1

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-29 13:41:07 UTC ---
confirmed

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[vhaisman at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Václav Zeman <vhaisman at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|4.4.1                       |4.7.0

--- Comment #6 from Václav Zeman <vhaisman at gmail dot com> 2012-03-29 17:39:40 UTC ---
This still fails for gcc version 4.7.0 20120225.

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #7 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2012-03-29 19:58:34 UTC ---
Clang prints:

/tmp/webcompile/_25725_0.cc:15:5: error: call to constructor of 'S' is
ambiguous
  S s1 ("test");
    ^   ~~~~~~
/tmp/webcompile/_25725_0.cc:4:3: note: candidate constructor [with T = char]
  S (T const *)
  ^
/tmp/webcompile/_25725_0.cc:8:3: note: candidate constructor [with N = 5]
  S (char const (&)[N])
  ^
/tmp/webcompile/_25725_0.cc:1:8: note: candidate is the implicit copy
constructor
struct S
       ^
1 error generated.

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |dodji at gcc dot gnu.org
                   |gnu.org                     |

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[dodji at seketeli dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

--- Comment #8 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-03-31 17:02:48 UTC ---
A candidate fix was posted to
http://gcc.gnu.org/ml/gcc-patches/2012-03/msg01993.html for review.

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

--- Comment #9 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-04-02 08:51:30 UTC ---
Author: dodji
Date: Mon Apr  2 08:51:26 2012
New Revision: 186067

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186067
Log:
PR c++/40942 - Failure of template specialization partial ordering

gcc/cp/

    * pt.c (more_specialized_fn):  Don't apply decay conversion to
    types of function parameters.

gcc/testsuite/

    * g++.old-deja/g++.pt/spec40.C: Adjust to take the resolution of
    DR 214 in account.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.old-deja/g++.pt/spec40.C

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

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

--- Comment #10 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-04-02 08:56:24 UTC ---
Fixed in 4.8 (trunk).

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.0

[Bug c++/40942] New: GCC accepts code that Comeau and MSVC deems invalid.

[v dot haisman at sh dot cvut dot cz]

The following test case compiles with GCC, it chooses the second ctor. Both
MSVC8 and Comeau reject it complaining about overload ambiguity.


#include <cstdlib>

template <bool B, class T = void>
struct enable_if_c {
  typedef T type;
};

template <class T>
struct enable_if_c<false, T> {};

template <class Cond, class T = void>
struct enable_if : public enable_if_c<Cond::value, T> {};


struct true_type
{
  enum { value = 1 };
};


struct false_type
{
  enum { value = 0 };
};


template <typename T, typename U>
struct is_same
  : public false_type
{ };


template <typename T>
struct is_same<T, T>
  : public true_type
{ };


struct S
{
  template <typename T>
  S (T const *,
     typename enable_if<is_same<char, T>, T *>::type = 0)
  { }

  template <size_t N>
  S (char const (&)[N])
  { }
};

int
main()
{
  char array[] = "test";

  S s1 ("test");
  S s2 (array);
}


-- 
           Summary: GCC accepts code that Comeau and MSVC deems invalid.
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: v dot haisman at sh dot cvut dot cz
 GCC build triplet: x86_64-portbld-freebsd7.1
  GCC host triplet: x86_64-portbld-freebsd7.1
GCC target triplet: x86_64-portbld-freebsd7.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[jwakely dot gcc at gmail dot com]

------- Comment #1 from jwakely dot gcc at gmail dot com  2009-08-04 12:48 -------
Testcase can be reduced to:

struct S
{
  template <typename T>
  S (T const *)
  { }

  template <size_t N>
  S (char const (&)[N])
  { }
};

int
main()
{
  S s1 ("test");
}

GCC still accepts this while Comeau rejects it.


-- 

jwakely dot gcc at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jwakely dot gcc at gmail dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[bangerth at gmail dot com]

------- Comment #2 from bangerth at gmail dot com  2009-08-25 13:24 -------
Why would this be ambiguous? A string literal has type "array of n const char"
(see 2.13.4/1), so it should go with the array constructor. Do you disagree?

W.


-- 

bangerth at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[v dot haisman at sh dot cvut dot cz]

------- Comment #3 from v dot haisman at sh dot cvut dot cz  2009-08-25 14:20 -------
(In reply to comment #2)
> Why would this be ambiguous? A string literal has type "array of n const char"
> (see 2.13.4/1), so it should go with the array constructor. Do you disagree?
> 
> W.
> 
IANALL, but I think this might be the reason:

The conversion sequence for S (T const *) is array-to-pointer conversion as per
4.2. The conversion sequence for S (char const (&)[N]) is lvalue-to-rvalue
conversion. For both the ranks are the exact match and thus they are
indistinguishable conversion sequences as per 13.3.3.2?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942

[Bug c++/40942] GCC accepts code that Comeau and MSVC deems invalid.

[tom at kera dot name]

------- Comment #4 from tom at kera dot name  2009-08-25 14:48 -------
(In reply to comment #2)
> Why would this be ambiguous? A string literal has type "array of n const char"
> (see 2.13.4/1), so it should go with the array constructor. Do you disagree?
> 
> W.
> 

Table 9 under 13.3.3/1 shows that array-to-pointer conversion is Exact Match.
As is rvalue-to-lvalue conversion (though string literals are lvalues anyway
:D). As is Identity, which is what applies here.

There is no clear ranking between them, hence Comeau reporting ambiguity.
Although I personally think Identity should overrule absolutely everything, it
doesn't. So IMO GCC is buggy in this way.


-- 

tom at kera dot name changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tom at kera dot name


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40942