[MinGW-notify] [ mingw-Bugs-917257 ] optimization bug - wrong indirection with shared libraries

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Bugs item #917257, was opened at 2004-03-16 03:57
Message generated for change (Settings changed) made by earnie
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https://sourceforge.net/tracker/?func=detail&atid=102435&aid=917257&group_id=2435

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Category: None
Group: None
>Status: Closed
Resolution: None
Priority: 5
Private: No
Submitted By: Sebastian Tusk (sebastiantusk)
Assigned to: Nobody/Anonymous (nobody)
Summary: optimization bug - wrong indirection with shared libraries

Initial Comment:
I have here a problem with optimization option -O1
generates corrupt code. Using a linux(debian-unstable)
machine to cross-compile for windows the below shown
sample code gives strange results with -O1. Without -O1
anything seems fine.

Two calls into a shared library are in the sample code.
In this case the library is Python but it happens also
with xerxces. The problem is not restricted to function
calls. Pointers to variables in the shared library
causes the problem too.

As you may notice from the below shown assembler output
the first call (Py_Initialize()) is compiled into
004012ba a1b4404000       mov    
eax,[image00400000+0x40b4 (004040b4)]
004012bf ffd0             call    eax
for the unoptimized version and
004012ba ff15b4404000     call    dword ptr
[image00400000+0x40b4 (004040b4)]
for the optimized. That is correct and works.

But the second call (Py_InitModule4( NULL, NULL, NULL,
NULL, 0x123 )) is compiled into
004012c5 c744241023010000 mov     dword ptr
[esp+0x10],0x123
004012cd c744240c00000000 mov     dword ptr [esp+0xc],0x0
004012d5 c744240800000000 mov     dword ptr [esp+0x8],0x0
004012dd c744240400000000 mov     dword ptr [esp+0x4],0x0
004012e5 c7042400000000   mov     dword ptr [esp],0x0
004012ec a1b0404000       mov    
eax,[image00400000+0x40b0 (004040b0)]
004012f1 ffd0             call    eax
for the unoptimized version and
004012c4 c744241023010000 mov     dword ptr
[esp+0x10],0x123
004012cc c744240c00000000 mov     dword ptr [esp+0xc],0x0
004012d4 c744240800000000 mov     dword ptr [esp+0x8],0x0
004012dc c744240400000000 mov     dword ptr [esp+0x4],0x0
004012e4 c7042400000000   mov     dword ptr [esp],0x0
004012eb e8c02d0000       call    image00400000+0x40b0
(004040b0)
for the optimized.

You see that the optimized call doesn't have the
indirection necessary to call a function in a shared
library. The same indirection that is done correctly in
the first call (Py_Initialize()). The program crashes
at this point as you may imagine.

I have no idea for which calls the problem occurs. Some
calls work some not. I think this is a compiler bug but
maybe I overlook something.

Should I post this mail to the gcc developers too?

Regards,
Sebastian

  *** compiler command
g++ -b i586-mingw32msvc -V 3.3.1
-I../the_fall/libs/Python-2.2.3/Include -masm=intel
test2.cpp -fno-exceptions -L../libs/Python-2.2.3/libs/
-lpython22

  *** sample code
#include <windows.h>
#include "Python.h"

int WINAPI WinMain( HINSTANCE hInstance,
        HINSTANCE hPrevInstance,
        LPSTR lpCmdLine,
        int nCmdShow )
{
        asm( "nop; nop; nop; int 3" );
        Py_Initialize();
        asm( "nop; nop; nop; int 3" );
        Py_InitModule4( NULL, NULL, NULL, NULL, 0x123 );
        asm( "nop; nop; nop; int 3" );

        return 0;
}

  *** without -O1 option
004012b6 90               nop
004012b7 90               nop
004012b8 90               nop
004012b9 cc               int     3
004012ba a1b4404000       mov    
eax,[image00400000+0x40b4 (004040b4)]
004012bf ffd0             call    eax
004012c1 90               nop
004012c2 90               nop
004012c3 90               nop
004012c4 cc               int     3
004012c5 c744241023010000 mov     dword ptr
[esp+0x10],0x123
004012cd c744240c00000000 mov     dword ptr [esp+0xc],0x0
004012d5 c744240800000000 mov     dword ptr [esp+0x8],0x0
004012dd c744240400000000 mov     dword ptr [esp+0x4],0x0
004012e5 c7042400000000   mov     dword ptr [esp],0x0
004012ec a1b0404000       mov    
eax,[image00400000+0x40b0 (004040b0)]
004012f1 ffd0             call    eax
004012f3 90               nop
004012f4 90               nop
004012f5 90               nop
004012f6 cc               int     3

  *** with -O1 option
004012b6 90               nop
004012b7 90               nop
004012b8 90               nop
004012b9 cc               int     3
004012ba ff15b4404000     call    dword ptr
[image00400000+0x40b4 (004040b4)]
004012c0 90               nop
004012c1 90               nop
004012c2 90               nop
004012c3 cc               int     3
004012c4 c744241023010000 mov     dword ptr
[esp+0x10],0x123
004012cc c744240c00000000 mov     dword ptr [esp+0xc],0x0
004012d4 c744240800000000 mov     dword ptr [esp+0x8],0x0
004012dc c744240400000000 mov     dword ptr [esp+0x4],0x0
004012e4 c7042400000000   mov     dword ptr [esp],0x0
004012eb e8c02d0000       call    image00400000+0x40b0
(004040b0)
004012f0 90               nop
004012f1 90               nop
004012f2 90               nop
004012f3 cc               int     3 

----------------------------------------------------------------------

Comment By: Danny Smith (dannysmith)
Date: 2004-03-16 11:52

Message:
Logged In: YES 
user_id=11494

This is what I get with g++-3.4.0 at -O1 -masm=intel

Danny

	.file	"test2.ii"
	.intel_syntax
	.text
	.align 2
.globl _WinMain@16
	.def	_WinMain@16;	.scl	2;	.type
	32;	.endef
_WinMain@16:
	push	ebp
	mov	ebp, esp
	sub	esp, 24
/APP
	nop; nop; nop; int 3
/NO_APP
	call	[DWORD PTR __imp__Py_Initialize]
/APP
	nop; nop; nop; int 3
/NO_APP
	mov	DWORD PTR [esp+16], 291
	mov	DWORD PTR [esp+12], 0
	mov	DWORD PTR [esp+8], 0
	mov	DWORD PTR [esp+4], 0
	mov	DWORD PTR [esp], 0
	call	DWORD PTR __imp__Py_InitModule4
/APP
	nop; nop; nop; int 3
/NO_APP
	mov	eax, 0
	leave
	ret	16

----------------------------------------------------------------------

Comment By: Sebastian Tusk (sebastiantusk)
Date: 2004-03-16 07:05

Message:
Logged In: YES 
user_id=999113

I have found that ommitting the -masm=intel command line
option solves the problem.

----------------------------------------------------------------------

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