free pointer to chars

[cfdprogrammer]

Hi all,

I am having a problem I never had before when deallocating a pointer to char. I am not sure what I am doing wrong because I am using the same standard I have used other times.

I am declaring and allocating the following variable:

char   *problem[10];

//Allocation of the strings of the above lines:
  for(i=0; i<10; i++)
    problem[i] = (char *) malloc(32 * sizeof(char *));

and after it use, I free it by:

  for(i=0; i<10; i++)
    free(problem[i]);

but I get the following error:

malloc: *** error for object 0x200000: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug

Could anyone help me with this?

thank you in advance,
cfd

[laserlight]

This is wrong:

problem[i] = (char *) malloc(32 * sizeof(char *));

It should be:

problem[i] = malloc(32 * sizeof(char));

or better yet:

problem[i] = malloc(32 * sizeof(problem[i][0]));

or since sizeof(char) == 1:

problem[i] = malloc(32);

though you probably should use a named constant instead of directly using 32.

[cfdprogrammer]

Hi, thanks for replying, but although I change the allocation following your suggestion, I am still getting the error the the pointer I am freeing was not allocated to begin with.

I don't know where the actual problem would be since I am not freeing it twice throughout the code.

Thanks again

[cfdprogrammer]

Apologies,

I was deallocating another array within another function. That is what was causing the problem.

Thanks again for helping.
cfd

[laserlight]

So, this results in the error that you were talking about?

#include <stdlib.h>

int main(void)
{
    char *problem[10];
    int i;

    for (i = 0; i < 10; i++)
        problem[i] = malloc(32 * sizeof(problem[i][0]));

    for (i = 0; i < 10; i++)
        free(problem[i]);

    return 0;
}