[Bug c++/54895] New: the compiler treats '__cdecl' & '__stdcall' as the same.

[Bug c++/54895] New: the compiler treats '__cdecl' & '__stdcall' as the same.

[i.nixman at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

             Bug #: 54895
           Summary: the compiler treats '__cdecl' & '__stdcall' as the
                    same.
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: i.nixman@gmail.com


When I compile this simple code:
void myfoo(void(__cdecl*)()){}
void myfoo(void(__stdcall*)()){}
int main(){}


I get the following error:
Assembler messages:
Error: symbol `__Z5myfooPFvvE' is already defined

Why the compiler treats theese two specificators as the same?


Another example code work as expected:
template<typename T, typename U>
struct is_same {
        enum { value = 0 };
};

template<typename T>
struct is_same<T, T> {
        enum { value = 1 };
};

int main() {
        typedef void(__stdcall* stdcall_func_ptr)();
        typedef void(__cdecl* cdecl_func_ptr)();

        return is_same<stdcall_func_ptr, cdecl_func_ptr>::value;
}

main returns 0

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[i.nixman at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #1 from niXman <i.nixman at gmail dot com> 2012-10-10 19:53:48 UTC ---
used i686-w64-mingw32

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[sezeroz at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

Ozkan Sezer <sezeroz at gmail dot com> changed:

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

--- Comment #2 from Ozkan Sezer <sezeroz at gmail dot com> 2012-10-10 20:17:26 UTC ---
FWIW, this is not specific to 4.7 and goes back to at least 4.4.

[Bug target/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> 2012-10-10 20:52:38 UTC ---
Related to PR c++/2316. Those attributes are properly supported in C but not
with fancy C++ features. I don't think they have a mangling, for instance.

[Bug target/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

Kai Tietz <ktietz at gcc dot gnu.org> changed:

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

--- Comment #4 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-22 11:47:12 UTC ---
This is most likely a duplicate of already fixed PR/55268.

[Bug target/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[i.nixman at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #5 from niXman <i.nixman at gmail dot com> 2012-11-22 18:37:55 UTC ---
(In reply to comment #4)
> This is most likely a duplicate of already fixed PR/55268.

I checked upon the 193725 revision.
The first test gives the same result. The second test now gives the wrong
result(1). Before this the result of the second test was right.

[Bug target/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-11-22
     Ever Confirmed|0                           |1

--- Comment #6 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-22 18:48:18 UTC ---
(In reply to comment #5)
> (In reply to comment #4)
> > This is most likely a duplicate of already fixed PR/55268.
> 
> I checked upon the 193725 revision.
> The first test gives the same result. The second test now gives the wrong
> result(1). Before this the result of the second test was right.

Well, the first test fails due the calling-convention isn't part of the
signature in C++.  For C you will get for this code simply a double-definition.
 Issue here is that we don't get an error for g++ as it detects that a types
are different for both myfoo functions.

The second case checks something different. That it now returns 1 is correct
due types are different due different calling-convention used.

So remaining testcase is the first one.

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |c++
      Known to work|                            |4.4.0, 4.5.0, 4.6.0, 4.7.0,
                   |                            |4.8.0

--- Comment #7 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-22 18:55:40 UTC ---
it is actual not a target issue.  it is more a general c++ issue as
calling-convention (call-abi attributes) aren't part of signature.

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-11-22 19:08:14 UTC ---
So it works everywhere? ;)

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #9 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-22 19:11:12 UTC ---
(In reply to comment #8)
> So it works everywhere? ;)

Well, it doesn't work for all targets providing different calling-conventions
for functions.  Eg functions with regparm, stdcall, etc
That the sample is architecture specific, doesn't make it there for target
specific, isn't it? ;)

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #10 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-11-22 19:14:03 UTC ---
I don't know, I'm still finding the "Known to work" field pretty weird, to be
honest.

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|4.4.0, 4.5.0, 4.6.0, 4.7.0, |
                   |4.8.0                       |
      Known to fail|                            |4.4.0, 4.5.0, 4.6.0, 4.7.0,
                   |                            |4.8.0

--- Comment #11 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-11-22 19:15:49 UTC ---
heh, oh duhh :}

[Bug c++/54895] the compiler treats '__cdecl' & '__stdcall' as the same.

[ktietz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54895

--- Comment #12 from Kai Tietz <ktietz at gcc dot gnu.org> ---
This bug got partially fixed for x86 (32-bit) by PR/44282.  For x64 we have the
issue that there is made no difference between different calling-conventions,
as all variants are treated as standard fastcall-convention under the hood.