[Bug c++/15774] New: Conflicting function decls not diagnosed

[Bug c++/15774] New: Conflicting function decls not diagnosed

[dannysmith at users dot sourceforge dot net]

The C++ frontend doesn't always call targetm.compare_type_attributes
when comparing function decls in decl.c: decls_match.  As a result
conflicting decls are not diagnosed.  Here is a testcase.

/* stdcall.c */
extern void foo(int);

void bar() { foo(1);}

void __attribute__((stdcall)) foo(int i) {};

This should casue fatal error because of type conflict between
declaration and definition of foo.

In C it does.

D:\develop\bugs>gcc -S -Wall stdcall.c 
> stdcall.c:5: error: conflicting types for 'foo'
> stdcall.c:1: error: previous declaration of 'foo' was here

In C++ it doesn't

D:\develop\bugs>gcc -xc++ -S -Wall stdcall.c
compiles without error.

But it produces bad code.  This is easier to spot on windows targets because
of the target specific stdcall decoration.

        .file        "stdcall.c"
        .text
        .align 4
        .align 2
.globl __Z3barv
        .def        __Z3barv;        .scl        2;        .type        
32;        .endef
__Z3barv:
        pushl        %ebp
        movl        %esp, %ebp
        subl        $8, %esp
        subl        $12, %esp
        pushl        $1
        call        __Z3fooi   <<< undefined
        addl        $16, %esp  <<< Should be $12.
        leave
        ret
        .align 2
.globl __Z3fooi@4
        .def        __Z3fooi@4;        .scl        2;        .type        
32;        .endef
__Z3fooi@4:
        pushl        %ebp
        movl        %esp, %ebp
        leave
        ret        $4
        .def        __Z3fooi;        .scl        3;        .type        
32;        .endef


The testcase fails in 3.4.0 and 3.5.0 on i386-i386-pc-mingw32


The following patch to cp/declc fixes the testcase.  I don't think it is right, 
but I'll run it throw bootstrap and regtest and  submit proper patch if it 
doesn't cause any other problems.

Danny

Index: decl.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/decl.c,v
retrieving revision 1.1212
diff -c -3 -p -r1.1212 decl.c
*** decl.c	28 May 2004 21:58:15 -0000	1.1212
--- decl.c	2 Jun 2004 10:35:33 -0000
*************** decls_match (tree newdecl, tree olddecl)
*** 1021,1027 ****
  	    }
  #endif
  	  else
! 	    types_match = compparms (p1, p2);
  	}
        else
  	types_match = 0;
--- 1021,1030 ----
  	    }
  #endif
  	  else
! 	    types_match = compparms (p1, p2)
! 			  && comptypes (TREE_TYPE (newdecl),
! 					 TREE_TYPE (olddecl),
! 					 COMPARE_REDECLARATION);
  	}
        else
  	types_match = 0;

-- 
           Summary: Conflicting function decls not diagnosed
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dannysmith at users dot sourceforge dot net
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-pc-mingw32
  GCC host triplet: i386-pc-mingw32
GCC target triplet: i386-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[dannysmith at users dot sourceforge dot net]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |2.95.3 3.3.3 3.4.0 3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-02 11:37 -------
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-06-02 11:37:54
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-06-28 01:04 -------
Danny,

did you test the patch? What was the outcome?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |giovannibajo at libero dot
                   |                            |it


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[dannysmith at users dot sourceforge dot net]

------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-06-28 01:42 -------
Yes I did test it and it was wrong, because it appears  C++ front end handles 
attributes of class member functions differently than global functions. 
Attributes of member functions are only honoured when declared within class 
definition,  which makes sense to me.  So for something like this (g++-old-
deja/g++.ext/attrib2.C) my patch would cause an error to be emitted.  Should it?
Should C++ require (as does C) that the subsequent definition also have an 
explicit attribute?

// { dg-do run { target i?86-*-* } }
// Test that stdcall doesn't prevent us from using op delete.
// Contributed by Jason Merrill <jason@cygnus.com>

struct A {
  void operator delete (void *) __attribute__ ((stdcall));
};

void foo()
{
  A* ap = new A;
  delete ap;
}

void  A:: operator delete (void *)  { }

int main()
{
  A* ap = new A;
  delete ap;
}

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-06-28 07:40 -------
I think the idea is that if you *ADD* an attribute in a later redeclaration, 
you should get an error (like in your testcase), but if you omit it in the 
redeclaration it is ok (the attribute is implicit in that case).

// OK
void foo(void) stdcall;
void foo(void) {}

// OK
void bar(void) stdcall;
void bar(void) stdcall {}

// ERROR
void foobar(void);
void foobar(void) stdcall {}


Jason, would you kindly comment on this? We need to know which way to proceed 
with this patch.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at redhat dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[jason at redhat dot com]

------- Additional Comments From jason at redhat dot com  2004-06-29 03:03 -------
Subject: Re:  Conflicting function decls not diagnosed

On 28 Jun 2004 07:40:43 -0000, "giovannibajo at libero dot it" <gcc-bugzilla@gcc.gnu.org> wrote:

> I think the idea is that if you *ADD* an attribute in a later
> redeclaration, you should get an error (like in your testcase), but if
> you omit it in the redeclaration it is ok (the attribute is implicit in
> that case).

> Jason, would you kindly comment on this? We need to know which way to proceed 
> with this patch.

That makes sense to me as a general rule.

Jason


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

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

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

--- Comment #9 from Kai Tietz <ktietz at gcc dot gnu.org> 2011-02-19 21:26:39 UTC ---
After discussing in more detail with Jason, I'll close this bug as fixed.

[Bug c++/15774] Conflicting function decls not diagnosed

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ktietz at gcc dot gnu.org
         AssignedTo|dannysmith at users dot     |ktietz at gcc dot gnu.org
                   |sourceforge.net             |
      Known to fail|                            |

--- Comment #8 from Kai Tietz <ktietz at gcc dot gnu.org> 2011-01-13 21:40:17 UTC ---
This bug is fixed on trunk (4.6) version. But the final solution needs some
more work, so that those kind of issues are handled in type-comparision
directly and double code (as present in the moment) can be avoided.

[Bug c++/15774] Conflicting function decls not diagnosed

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

--- Comment #7 from Kai Tietz <ktietz at gcc dot gnu.org> 2010-12-25 10:41:09 UTC ---
Author: ktietz
Date: Sat Dec 25 10:41:05 2010
New Revision: 168241

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=168241
Log:
2010-12-25  Kai Tietz  <kai.tietz@onevision.com>

    PR c++/15774
    * decl.c (decls_match): Check for FUNCTION_DECL
    also for identity of compatible attributes.


ChangeLog gcc/testsuite

2010-12-25  Kai Tietz  <kai.tietz@onevision.com>

    PR c++/15774
    * g++.dg/warn/pr15774-1.C: New test.
    * g++.dg/warn/pr15774-2.C: New test.


Added:
    trunk/gcc/testsuite/g++.dg/warn/pr15774-1.C
    trunk/gcc/testsuite/g++.dg/warn/pr15774-2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/15774] Conflicting function decls not diagnosed

[dannysmith at users dot sourceforge dot net]

------- Comment #6 from dannysmith at users dot sourceforge dot net  2007-09-19 21:52 -------
With 4.1, 4.2 and trunk, there is still no diagnosis of change in calling
convention in decl,  but the bug in generated code is exposed only with
-fno-unit-at-time.
Danny


-- 

dannysmith at users dot sourceforge dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|2.95.3 3.3.3 3.4.0 4.0.0    |2.95.3 3.3.3 3.4.0 4.0.0
                   |                            |4.1.0 4.2.1 4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774

[Bug c++/15774] Conflicting function decls not diagnosed

[dannysmith at users dot sourceforge dot net]

-- 

dannysmith at users dot sourceforge dot net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dannysmith at users dot
                   |dot org                     |sourceforge dot net
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2005-04-30 16:18:12         |2006-06-30 02:48:45
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15774