Can't set C char array element

Question

I have try set one of array item to specific value. The program is compiled but when I execute it return segfault.

Here is the code:

#include <stdio.h>

void Debug(unsigned char* str, char simbol, char size);


int main() {

  Debug((unsigned char*)"DEBUG: message: x\r\n", 'e', 40);
  return(0);

}

//this function I try to replace all occurrences of x with simbol value 'e'

void Debug (unsigned char* str, char simbol, char size){
    char i;

    for (i = 0 ; i < size ; i++){
        if( str[i] == 'x' ){
            str[i] = simbol;
        }
    }
    printf ("%s\n",  str);
}

Thanks in advance for any help !

#include #include void Debug(unsigned char* str, char simbol, char size); int main() { unsigned char * mumu; mumu = malloc(sizeof(unsigned char)*40); mumu = "DEBUG: message: x\r\n"; Debug(mumu, 'e', 40); return(0); } void Debug (unsigned char* str, char simbol, char size){ int i; unsigned char * mumu2; mumu2 = malloc(sizeof(unsigned char)*40); strcpy(mumu2,str); for (i = 0 ; i < size ; i++){ if( str[i] == 'x' ){ mumu2[i] = simbol; }} printf ("%s\n", mumu2); return; } THIS IS A WORKING CODE — Dimitri, Feb 13 '15 at 09:57

score 0 · Answer 1 · answered Feb 13 '15 at 08:45

0

unsigned char* str

Here str is read-only and you are trying to write to this location hence segmentation fault.

Have a array

unsigned char str[100] = "DEBUG: message: x\r\n";

and pass this array to the function.

answered Feb 13 '15 at 08:45

Gopi

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Thank you! With predefined array it work perfect. – TonyMony Feb 16 '15 at 06:27
@TonyMony Yes that should work...:) You can mark this answered – Gopi Feb 16 '15 at 06:29

score 0 · Answer 2 · answered Feb 13 '15 at 08:46

0

You try to modify a const object (the string). This is the reason, why you had to cast the string to unsigned char* in the first place. To solve this,you have to copy that string into a char array first.

answered Feb 13 '15 at 08:46

MikeMB

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Can't set C char array element

2 Answers2