CODEWITHSUNDEEP
cgcc-warning
static_sid
static_sid

Reputation: 23

How to fix the "[something] may be used uninitialized in this function" warning?

I am trying to make string copy command but I am getting the compilation warning (see the title) when compiling the program. If I compile the code without -Wall option than it gives me the correct output but I want to compile it with -Wall and get no warnings. How do I solve my issues? I already googled it but I didn't understand it.

When I initialise str2 to NULL or 0 it gives me seg fault.

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

void my_strcpy(char *dest[], const char *src[]);

int main(){

  char *str1, *str2;
  int i;

  printf("What is the longest length of a string that you will enter?");
  scanf("%i",&i);

  str1=malloc(i * sizeof(char));
  if (str1 == NULL){
    printf("\n malloc failed to allocate enough memory!\n");
    return 1;
  }

  printf("Enter a string: ");
  scanf("%s", str1);

  my_strcpy(str2,str1);
  printf("%s \n", str1);
  return 0;
}

void my_strcpy(char *dest, const char *src)
{
  int i;

  for(i=0; src[i]!='\0'; i++)
    dest[i]=src[i];
}

I expect the output to display just one string for example:

text entered: hello world

output:

hello

Upvotes: 1

Views: 8488

Answers (1)

dash-o
dash-o

Reputation: 14452

There are few things that are needed to address compiler warning:

  1. Function prototype for my_strcpy. Considering matching the protytype to the implementation: void my_strcpy(char *dest, const char *src);, and NOT void my_strcpy(char *dest[], const char *src[]);

  2. Allocation for str2. It is declared as a pointer, but no assignment to a space was done. Consider adding str2 = malloc(i+1); or similar.

  3. Allocation for str1 (run time error, not compiler warning). Remember to add space for the terminal NUL bytes: str1=malloc((i+1) * sizeof(char)); instead of str1=malloc(i * sizeof(char));

Upvotes: 2

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