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List:       mingw-users
Subject:    Re: [Mingw-users] asprintf missing,
From:       Jonathan Schleifer <js-mingw-users () webkeks ! org>
Date:       2008-12-19 13:05:33
Message-ID: 20081219140533.2c14e1d9 () webkeks ! org
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Ok, I found out how to reprodue the problem. The -O2 flag is causing
the problem. Take a look at this:

asgard:/tmp$ cat asprintf.c            
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

int
asprintf(char **strp, const char *fmt, ...)
{
	int size;
	va_list args;

	va_start(args, fmt);

	if ((size = vsnprintf(NULL, 0, fmt, args)) < 0)
		return size;
	if ((*strp = malloc((size_t)size + 1)) == NULL)
		return -1;

	return vsnprintf(*strp, (size_t)size + 1, fmt, args);
}

int main()
{
	char *x;

	printf("ret: %d\n", asprintf(&x, "hello"));
	printf("ptr: %p\n", x);
	puts(x);

	return 0;
}
asgard:/tmp$ mingw32-gcc asprintf.c
asgard:/tmp$ wine a.exe 
ret: 5
ptr: 00110888
hello

Until here, everything works as expected. But look now at this (still
the same file):

asgard:/tmp$ mingw32-gcc -O2 asprintf.c
asgard:/tmp$ wine a.exe 
ret: -1
ptr: 00000000
wine: Unhandled page fault on read access to 0x00000000 at address 0xb7dd7ab3 (thread \
0009), starting debugger... Unhandled exception: page fault on read access to \
0x00000000 in 32-bit code (0xb7dd7ab3). Register dump:
 CS:0073 SS:007b DS:007b ES:007b FS:0033 GS:003b
 EIP:b7dd7ab3 ESP:0060fe5c EBP:0060fe88 EFLAGS:00010246(   - 00      -RIZP1)
 EAX:00000000 EBX:7ebe5d98 ECX:00000000 EDX:00000000
 ESI:00000000 EDI:00401130
Stack dump:
0x0060fe5c:  7ebc5995 00000000 00403033 0060fe94
0x0060fe6c:  0060fe98 000000fc 7ebe5d98 0060fea8
0x0060fe7c:  7eeb19c0 7ffdf000 00401130 0060feb8
0x0060fe8c:  004013d0 00000000 00000000 0060feb8
0x0060fe9c:  0040139a 7ebebdc8 00401130 0060fec8
0x0060feac:  7ebbc51c 00000000 0060fed0 0060fef8
Backtrace:
=>1 0xb7dd7ab3 strlen+0x33() in libc.so.6 (0x0060fe88)
  2 0x004013d0 in a (+0x13d0) (0x0060feb8)
  3 0x004010b6 in a (+0x10b6) (0x0060fef8)
  4 0x00401148 in a (+0x1148) (0x0060ff08)
  5 0x7ee74d97 start_process+0xc7(arg=0x0) \
[/tmp/wine-1.1.1/dlls/kernel32/process.c:904] in kernel32 (0x0060ffe8)  6 0xb7ed3587 \
wine_switch_to_stack+0x17() in libwine.so.1 (0x00000000) 0xb7dd7ab3 strlen+0x33 in \
libc.so.6: movl	0x0(%eax),%ecx Modules:
Module	Address			Debug info	Name (15 modules)
PE	  400000-  40a000	Export          a
ELF	7bf00000-7bf03000	Deferred        <wine-loader>
ELF	7eb99000-7ec01000	Deferred        msvcrt<elf>
  \-PE	7ebb0000-7ec01000	\               msvcrt
ELF	7ee01000-7ef2e000	Dwarf           kernel32<elf>
  \-PE	7ee20000-7ef2e000	\               kernel32
ELF	7ef2e000-7ef38000	Deferred        libnss_files.so.2
ELF	7ef38000-7ef5d000	Deferred        libm.so.6
ELF	7ef5d000-7f000000	Deferred        ntdll<elf>
  \-PE	7ef70000-7f000000	\               ntdll
ELF	b7d68000-b7d6c000	Deferred        libdl.so.2
ELF	b7d6c000-b7e9a000	Export          libc.so.6
ELF	b7e9a000-b7eb1000	Deferred        libpthread.so.0
ELF	b7ecc000-b8002000	Dwarf           libwine.so.1
ELF	b8003000-b801f000	Deferred        ld-linux.so.2
Threads:
process  tid      prio (all id:s are in hex)
00000008 (D) Z:\tmp\a.exe
	00000009    0 <==
0000000c 
	00000013    0
	00000012    0
	0000000e    0
	0000000d    0
0000000f 
	00000015    0
	00000014    0
	00000011    0
	00000010    0
Backtrace:
=>1 0xb7dd7ab3 strlen+0x33() in libc.so.6 (0x0060fe88)
  2 0x004013d0 in a (+0x13d0) (0x0060feb8)
  3 0x004010b6 in a (+0x10b6) (0x0060fef8)
  4 0x00401148 in a (+0x1148) (0x0060ff08)
  5 0x7ee74d97 start_process+0xc7(arg=0x0) \
[/tmp/wine-1.1.1/dlls/kernel32/process.c:904] in kernel32 (0x0060ffe8)  6 0xb7ed3587 \
wine_switch_to_stack+0x17() in libwine.so.1 (0x00000000)

So it seems mingw32-gcc uses a different vsnprintf when using -O2?

-- 
Jonathan


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