why is this code causing runtime error?

Question

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

int main()
{
  char *a = "Hello ";
  const char *b = "World";

  printf("%s", strcat(a, b));
  system("PAUSE");

  return EXIT_SUCCESS;
}

String literals are not modifyable. http://stackoverflow.com/questions/1614723/why-is-this-c-code-causing-a-segmentation-fault/1614739#1614739 — AnT, Jan 14 '10 at 08:19

score 7 · Accepted Answer · answered Jan 14 '10 at 08:19

7

Because you are writing data at a memory location that you do not own.

Indeed, when running strcat, you are appending the characters of string b right after the characters of string a. But you haven't claimed for the memory after the string a.

answered Jan 14 '10 at 08:19

Didier Trosset

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score 2 · Answer 2 · edited Jan 14 '10 at 08:30

2

When you are concatenating b to a you are writing into memory you didn't allocate,

edited Jan 14 '10 at 08:30

Dan Olson

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answered Jan 14 '10 at 08:19

Alon

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why is this code causing runtime error?

2 Answers2