CODEWITHSUNDEEP
cstringmallocdynamic-memory-allocationfree
avivgood2
avivgood2

Reputation: 237

Freeing string untill null terminator

Assume I have a struct

struct 
foo{
char *p1;
char *p2;
char *p3;
}foo;

and I have assigned the struct malloc - allocated string line that

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

char temp[] = "this is string"
char *allocated_temp = malloc(sizeof(temp));
strcpy(allocated_temp, temp);

struct foo bar; 
bar.p1 = strtok(allocated_temp, " ");
bar.p2 = strtok(NULL, " ");
bar.p3 = strtok(NULL, " ");

I want to free p1 without freeing the other memory that is pointed to by p2 and p3. using realloc will not work as p3 will be freed first, and I am searching for a more of a elegant solution than using coping the struct to a new one without the first part or reallocating the other two strings to a different address.

What good solutions does this problem have?

(to clarify, when I am saying I want to free p1 i mean the "this\0" part of the string.

Upvotes: 1

Views: 516

Answers (1)

xhienne
xhienne

Reputation: 6144

There is no solution to your problem with standard tools (malloc, etc). You can only free the end of the memory that was allocated by realloc()-ing with a smaller size.

If you want to free p1 this way, you must first move your data to the beginning of the allocated block, update your pointers (p2 and p3) and then call realloc().

The best way is probably to change your program in order to malloc p1, p2 and p3 separately.

Upvotes: 1

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