How to get length of contiguous memory pointed at by char* after initializing it with malloc?

Question

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

int main()
{
    char* buffer = malloc(1000*sizeof(char));
    memset(buffer,'\0',1000);

    printf("%ld\n",sizeof buffer);    // Size of Pointer
    printf("%ld\n",sizeof *buffer);   // Size of Memory Block pointed at by buffer
    printf("%ld\n",strlen(buffer));   // Length of String
    return 0;
}


//  Output:-
//  8
//  1
//  0

The code works fine.

The output is as expected, but how do I find the length of contiguous memory that I initialized with malloc if I don't know the length?

You have to give the memory size to malloc, so how can you be in situation where you don't know the size ? — Ôrel, Jun 08 '20 at 12:11
I guess that was bad coding on my part, I should've allocated the memory in the function I used it in and passed it around for modification. — asds_asds, Jun 08 '20 at 12:14

score 4 · Answer 1 · answered Jun 08 '20 at 12:11

4

There's no standard way to find out how large a block of malloc'ed memory is.

It's up to you to keep track of the size yourself.

answered Jun 08 '20 at 12:11

dbush

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How to get length of contiguous memory pointed at by char* after initializing it with malloc?

1 Answers1