[Bug c++/16030] New: [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[Bug c++/16030] New: [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[dannysmith at users dot sourceforge dot net]

The  decoration of stdcall symbols in winnt.c:i386_pe_encode_section_info
causesa problems with the use of static aliases for MI thunks in
cp/method.c 

This problem is in 3.4.1 and trunk.

Consider this testcase:

// stdcall_thunk.C
class  MBase
{
public:
  virtual int __attribute__((stdcall)) vf() const = 0;
  virtual ~MBase() {};
};

class D1 : virtual public MBase
{
public:
  int __attribute__((stdcall)) vf() const;
};

class M1: public D1
{
public:
  int __attribute__((stdcall)) vf() const;
};

int D1::vf() const { return 1; }
int M1::vf() const { return D1::vf();}


This produces the assembly:

	.file	"stdcall_thunk.C"
	.def	LTHUNK0@4;	.scl	3;	.type	32;	.endef
	.set	LTHUNK0@4,__ZNK2D12vfEv  <<< not decorated

[...]

.globl __ZNK2D12vfEv@4  <<< stdcall decoration
	.def	__ZNK2D12vfEv@4;	.scl	2;	.type	32;	.endef
__ZNK2D12vfEv@4: 
	pushl	%ebp
	movl	%esp, %ebp
	movl	$1, %eax
	leave
	ret	$4
[...]


Note that although the D1::vf name has the correct stdcall decoaration,
the target of LTHUNK0@4 does not.

Although ld actually has an option to fix-up stdcall symbols to
the undecorated name, using that option can mask stack corruption bugs
until the app is actually run.

One way to fix is to use the RTL name rather than DECL_ASSEMBLER_NAME in
make alias_for_thunk, ie:

Index: method.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/method.c,v
retrieving revision 1.285
diff -c -3 -p -r1.285 method.c
*** method.c	16 Jun 2004 01:21:31 -0000	1.285
--- method.c	17 Jun 2004 02:41:09 -0000
*************** make_alias_for_thunk (tree function)
*** 314,320 ****
    SET_DECL_ASSEMBLER_NAME (alias, DECL_NAME (alias));
    TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (alias)) = 1;
    if (!flag_syntax_only)
!     assemble_alias (alias, DECL_ASSEMBLER_NAME (function));
    return alias;
  }
  
--- 314,330 ----
    SET_DECL_ASSEMBLER_NAME (alias, DECL_NAME (alias));
    TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (alias)) = 1;
    if (!flag_syntax_only)
!     {
!       /* Using DECL_ASSEMBLER_NAME to get the identifier for the alias
! 	 target loses any decoration that targetm.encode_section_info
! 	 may have added.  Use the RTL name instead.  */
!       tree idp;
!       /* Is this necessary?  */
!       if (!DECL_RTL_SET_P (function))
! 	make_decl_rtl (function, NULL);
!       idp = get_identifier (XSTR (XEXP (DECL_RTL (function), 0), 0));
!       assemble_alias (alias, idp);
!     }
    return alias;
  }
  


With above patch, I get this:

	.file	"stdcall_thunk.C"
	.def	LTHUNK0@4;	.scl	3;	.type	32;	.endef
	.set	LTHUNK0@4,__ZNK2D12vfEv@4  <<< OK

[...]

.globl __ZNK2D12vfEv@4
	.def	__ZNK2D12vfEv@4;	.scl	2;	.type	32;	.endef
__ZNK2D12vfEv@4:
	pushl	%ebp
	movl	%esp, %ebp
	movl	$1, %eax
	leave
	ret	$4


Is there a better way to do this?

Danny

-- 
           Summary: [cygwin/mingw]: stdcall function decoration vs LTHUNK
                    alias in multiple inheritanc
           Product: gcc
           Version: 3.4.1
            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: i686-pc-mingw32
  GCC host triplet: i686-pc-mingw32
GCC target triplet: i686-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[dannysmith at users dot sourceforge dot net]

------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-07-07 01:04 -------
Patch submitted:
http://gcc.gnu.org/ml/gcc-patches/2004-07/msg00534.html

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
            Summary|[cygwin/mingw]: stdcall     |[cygwin/mingw]: stdcall
                   |function decoration vs      |function decoration vs
                   |LTHUNK alias in multiple    |LTHUNK alias in multiple
                   |inheritanc                  |inheritanc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-07-07 01:07 -------
Since LTHUNK is new, this is a regression.
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-07-07 01:07:17
               date|                            |
            Summary|[cygwin/mingw]: stdcall     |[3.4/3.5 Regression]
                   |function decoration vs      |[cygwin/mingw]: stdcall
                   |LTHUNK alias in multiple    |function decoration vs
                   |inheritanc                  |LTHUNK alias in multiple
                   |                            |inheritanc
   Target Milestone|---                         |3.4.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2004-08-12 08:15 -------
Mark, can you review the patch at 
http://gcc.gnu.org/ml/gcc-patches/2004-07/msg00534.html? 
 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at codesourcery dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mark at codesourcery dot com]

------- Additional Comments From mark at codesourcery dot com  2004-08-12 14:35 -------
Subject: Re:  [3.4/3.5 Regression] [cygwin/mingw]: stdcall
 function decoration vs LTHUNK alias in multiple inheritanc

steven at gcc dot gnu dot org wrote:

>------- Additional Comments From steven at gcc dot gnu dot org  2004-08-12 08:15 -------
>Mark, can you review the patch at 
>http://gcc.gnu.org/ml/gcc-patches/2004-07/msg00534.html? 
>  
>
As a minor point, the get_identifier bit of that patch is very 
inefficient.  Instead, assemble_alias should be modified to take a "char 
*" argument, or a new function should be created that both 
assemble_alias and make_alias_fr_thunk can use.

But, a more major point is that I'm not at all confident that it's 
correct to use the encoded name on all targets.  Maybe 
ASM_OUTPUT_DEF_FROM_DECLS should be defined for these targets instead?



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[dannysmith at users dot sourceforge dot net]

------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-08-18 10:06 -------
cygming.h already does define ASM_OUTPUT_DEF_FROM_DECLS and it uses the RTL
encoded name for the new decl, but leaves the target of the alias alone. I don't
think it should modify the target,(at least in __attribute__ ((alias
("target"))) usage).

New patch submitted at:
http://gcc.gnu.org/ml/gcc-patches/2004-08/msg01320.html

Danny

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-08-19 21:21 -------
Patch OK, please commit.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4/3.5 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-08-21 08:02 -------
Subject: Bug 16030

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	dannysmith@gcc.gnu.org	2004-08-21 08:02:04

Modified files:
	gcc            : ChangeLog 
	gcc/config/i386: winnt.c 

Log message:
	PR  c++/16030
	* config/i386/winnt/c (gen_stdcall_suffix, gen_fastcall_suffix):
	Remove, merging into ...
	(gen_stdcall_or_fastcall_suffix): New function, returning tree
	rather than const char*, and accepting additional parameter.
	Don't add suffix to '*'-prefixed symbols or variadic functions.
	(i386_pe_encode_section_info): Adjust for call to new function.
	Call change_decl_assembler_name.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.5013&r2=2.5014
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/i386/winnt.c.diff?cvsroot=gcc&r1=1.70&r2=1.71



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[dannysmith at users dot sourceforge dot net]

------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-08-21 08:05 -------
Fixed on 3.5  The patch applies cleanly to 3.4.2.  OK there as well?
Danny

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|3.4.1 3.5.0                 |3.4.1
      Known to work|                            |3.5.0
            Summary|[3.4/3.5 Regression]        |[3.4 Regression]
                   |[cygwin/mingw]: stdcall     |[cygwin/mingw]: stdcall
                   |function decoration vs      |function decoration vs
                   |LTHUNK alias in multiple    |LTHUNK alias in multiple
                   |inheritanc                  |inheritanc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mark at codesourcery dot com]

------- Additional Comments From mark at codesourcery dot com  2004-08-23 06:54 -------
Subject: Re:  [3.4 Regression] [cygwin/mingw]: stdcall function
 decoration vs LTHUNK alias in multiple inheritanc

dannysmith at users dot sourceforge dot net wrote:

>------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-08-21 08:05 -------
>Fixed on 3.5  The patch applies cleanly to 3.4.2.  OK there as well?
>Danny
>
>  
>
OK.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-08-29 18:51 -------
Postponed until GCC 3.4.3.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.2                       |3.4.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-10-31 02:01 -------
Postponed until GCC 3.4.4.  

Although it's somewhat sad the patch has not yet been applied, given that I
approved it in August.  It's still OK to apply the patch, before 3.4.3, if
somebody wants to do that.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.3                       |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-10-31 02:05 -------
Danny, can you please quickly retest the patch and apply it immediatly to the 
branch? We might be still in time for 3.4.3.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[dannysmith at users dot sourceforge dot net]

------- Additional Comments From dannysmith at users dot sourceforge dot net  2004-10-31 02:37 -------
No, I won't backport this patch.  Although the patch did apply cleanly and 
fixed this bug,  using change_decl_assembler name caused warnings with mingw 
(in my code base, not in testsuite) that are not seen on trunk.  I'm sorry that 
I didn't report this immediately.  I'll try to sort it out before 3.4.4 but I 
do not see this as a high priority problem.

Danny

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030

[Bug c++/16030] [3.4 Regression] [cygwin/mingw]: stdcall function decoration vs LTHUNK alias in multiple inheritanc

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16030