Segmentation fault when trying to copy strings

[mobile-it]

#include <stdio.h>

int main(void){
char string[] = "hello\n";
char *p;
char *q;
q = string;


while(*p++=*q++)
;
printf("%s\n",q);
printf("%s\n",p);

return 0;
}

I get a segmentation fault when I try to run this program on ubuntu linux after compiled with gcc anyone knows the problem? I want to use this

 while(*p++=*q++)
;

instruction


thanks

 

[ace1903]

Pointer p is uninitialized p==NULL;
*(NULL)=value; probably causes segmentation fault. Try adding line p=(char *)malloc(max_string_lenght);

 

[jhbbunch]

You are using the assignment operator '=', you need to use the logical equal operator '==' :

You should use *p++ == *q++

Plus the pointer p was never assigned a valid address so it's address is NULL. So the statement will give an error. But even if p was assigned a valid address, the *p++ = *q++ statement by definition is always true so it won't terminate until the pointer p is incremented until it gives an error or just wraps around the segment to address 0 and so on ad nauseum..