segmentation fault when returning from this function

[johndoe444]

Hi,

For the following code segment I am getting segmentation fault:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char* trim(char* str)
{
	// while consecutive ws at the beginning skip
	int len = strlen(str);
	int i = 0,j = len-1,k,l = 0;
	
	while (str[i] == ' ' || str[i] == '\t' || str[i] == '\n' || str[i] == '\r') i++;
	// while consecutive ws at the end skip
	while (str[j] == ' ' || str[j] == '\t' || str[j] == '\n' || str[j] == '\r') j--;

	printf("i: %d, j: %d, len: %d\n",i,j,len);

	for (k = i;k <= j;k++)
	{
		str[l++] = str[k];
	}

	str[l] = '\0';

	printf("str: %s %d\n",str, strlen(str));
}

int main()
{
	char* str = (char*)malloc(10*sizeof(char));
	strcpy(str,"    abc \n");
	printf("str: %s\n",str);
	str = trim(str);	
	printf("str: %s\n",str);
	return 0;
}

str:     abc 
i: 4, j: 6, len: 9
str: abc 3
Segmentation fault

In this example *str in the trim is the same as the pointer *str in main (pointing to the same location). So I dont understand how come I get a segmentation fault.

In general it always baffles me what happens when a pointer is returned from within a function called by another function.

[gerard4143]

Number one, your trim function doesn't return anything...so if I had to guess str is getting whatever is in the eax/rax register..

str = trim(str);

[johndoe444]

Number one, your trim function doesn't return anything...so if I had to guess str is getting whatever is in the eax/rax register..

str = trim(str);

Thanks man. Silly mistake from me.