Segmentation fault (core dumped) in strtok [duplicate]

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Possible Duplicate:

Memory Allocation char* and char[]

Why does the开发者_运维百科 following program give a Segmentation fault in run-time ?

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

main()
{
    char * str = "Have a. nice, day :)";
    char * ptr;

    ptr = strtok( str, " .,");

    printf("%s",ptr);
 }

But if I use char str[] = "Have a. nice, day :)"; it gives me the output. Why is that i get the error even though strtok definition is char* strcpy( char * , const char * ) ???~

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strtok modifies the argument, str points to a string literal, modifying a string literal causes undefined behavior. Initializing a non-const char* with a string literal is in fact deprecated.

When you write str[], str becomes a mutable array initialized with the string.

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strtok modifies the string passed to it. I suspect it has something to do with char * = "literal string" giving you a pointer to the string in the .data section, while char[] = "literal string" allocates a buffer on the stack, and copies the initial contents from the .data section.