I wrote the following code to trim a char string at left. The code is
simple and I think there is no error, but when I run, I get
a "Segmentation fault". If I use the debugger (gdb), the error does
not occur. May anyone help me to understand why? and where is the
error?
Thanks a lot.
I am using a Red Hat distribution, version 7.3 and a cc release,
version 2.96.
== code start (ltrim.c) ==
#include <errno.h>
#include <string.h>
/* ltrim() function
* parameters:
* string = the string to trim at left
* return value:
* char* : the trimmed string at left
*/
char* ltrim(char *strn ){
if (strn!=NULL) {
char *p=strn;
char *tmp_buffer = NULL;
int l = strlen(p);
printf( "ltrim() : [%p] [%s], len: %d \n", p, p, l);
tmp_buffer = (char*) calloc( l+1, sizeof(char) );
if (tmp_buffer!=NULL) {
int x=0;
char c='\0';
printf("buffer before the filling: [%p] [%s] [%d]\n",
tmp_buffer, tmp_buffer, strlen(tmp_buffer) );
strcpy( tmp_buffer, p );
printf("buffer after the filling with the string: [%p] [%s] [%d]
\n", tmp_buffer, tmp_buffer, strlen(tmp_buffer) );
while ( (c=tmp_buffer[x++])!=0 && c==' ' ) {
printf("p: %d, c: [%c] 0X%2X\n",x, c, c);
}
printf( "reset string [%p], len: %d to 0\n", p, l );
memset((void*)p, 0, l );
printf("prepare the return parameter\n");
strcpy(p, &tmp_buffer[x-1]);
printf( "new string: [%s] l: %d -> free memory : [%p] [%s] [%d]
\n", p, strlen(p), tmp_buffer, tmp_buffer, strlen(tmp_buffer) );
free(tmp_buffer);
tmp_buffer = NULL;
printf( "memory freed\n");
printf( "ltrim() : (trimmed) [%s], len: %d \n", strn, strlen
(strn) );printf( "ltrim() : (trimmed) [%s], len: %d \n", strn, strlen
(strn) );
} else {
printf( "ltrim() : cannot allocate memory [%s] \n", strerror
(errno));
}
}
printf("return the value\n");
return (char*) strn;
}
int main (char **argz, char argc)
{
char *s0 = " bye 1 ";
char *d0 = ltrim(s0);
printf( "before: [%s] after [%s] \n", s0, d0 );
exit(0);
}
== code end ====
