Bug#263854: gcc-3.3: Generates bad code
Package: gcc-3.3
Version: 1:3.3.4-3
Severity: normal
-- System Information:
Debian Release: 3.1
APT prefers testing
APT policy: (500, 'testing')
Architecture: i386 (i686)
Kernel: Linux 2.4.24-bf2.4
Locale: LANG=C, LC_CTYPE=C
Versions of packages gcc-3.3 depends on:
ii binutils 2.14.90.0.7-8 The GNU assembler, linker and bina
ii cpp-3.3 1:3.3.4-3 The GNU C preprocessor
ii gcc-3.3-base 1:3.3.4-3 The GNU Compiler Collection (base
ii libc6 2.3.2.ds1-13 GNU C Library: Shared libraries an
ii libgcc1 1:3.3.4-3 GCC support library
-- no debconf information
The following code compiles badly for the my_strncpy_bug function : the
if( *tmp ) ++ tmp; is never generated.
The difference between both loops is the use of an inside loop temp
variable.
Execution :
sco@elton:/tmp$ gcc -O2 -o y y.c
sco@elton:/tmp$ ./y
t1:My First string for this test ... t2:
t1:My First string for this test ... t2:My First string for this test
....
t1:My First string for this test ... t2:
t1:My First string for this test ...
t2:MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMBefore buggy
sco@elton:/tmp$
--begining of source code for y.c
#include <stdio.h>
char *my_strncpy_bug( char *dst, const char *src, unsigned int n ) {
char *work = dst;
while( n ) {
const char *tmp = src;
*work = *tmp;
++ work;
if( *tmp )
++ tmp;
-- n;
}
return dst;
}
char *my_strncpy( char *dst, const char *src, unsigned int n ) {
char *work = dst;
while( n ) {
*work = *src;
++ work;
if( *src )
++ src;
-- n;
}
return dst;
}
int main( int argc, char **argv ) {
char tmp1[] = "My First string for this test ...";
char tmp_bug3[] = "Before buggy";
char tmp_bug2[256] = { 0 };
char tmp_nobug3[] = "Before no bug";
char tmp_nobug2[256] = { 0 };
printf( "t1:%s t2:%s\n", tmp1, tmp_nobug2 );
my_strncpy( tmp_nobug2, tmp1, 256 );
printf( "t1:%s t2:%s\n", tmp1, tmp_nobug2 );
printf( "t1:%s t2:%s\n", tmp1, tmp_bug2 );
my_strncpy_bug( tmp_bug2, tmp1, 256 );
printf( "t1:%s t2:%s\n", tmp1, tmp_bug2 );
return 0;
}
--end of source code for y.c
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