tralloc - track allocations

An C libray for tracking the size of heap-allocated memory blocks.

This is more of a proof-of-concept than anything and I wouldn't recommend using it in production. There's an accompanying article here: Tracking Allocations in C

Overview

This library provides several functions that act as wrappers around the stdlib memory allocation functions to provide information on the number of heap-allocated bytes for individual pointers and overall.

It's implemented with functions the act as stdlib wrappers so that it can sit ontop of whatever stdlib implementation you're using. The downside of this is that it's unable to track any allocations made without these wrappers.

There are also a few usability pitfalls:

• If you call some of the functions on pointers that have not been allocated by tralloc allocation functions, then it'll probably cause a memory error. This behaviour is consistent with stdlib though. Make sure to read function documentation.
• If you use a tralloc pointer to an address that wasn't returned by tralloc (either from incrementing/decrementing it), then it'll cause a memory error.

This was done more as a personal exercise than anything, most of the time in C you'll track allocated memory yourself. This was just a cool idea I got carried away with.

Goals

• Track the total number of heap-allocated bytes.
• Track number of bytes allocated for individual memory blocks.
• Don't get in the way of any users, behave as regular stdlib.

Guidelines

• Do not call tralloc_realloc(), tralloc_allocsiz() or tralloc_free on an address not returned by one of the tralloc stdlib wrapper functions.
• Don't expect tralloc to work on a non-tralloc pointer address.
• You should be able to use the tralloc stdlib wrappers just as you would use their stdlib counterparts without error.
• If you want to use malloc instead of tr_malloc, use a macro. See test.c for an example of this.
• It's experimental, so don't do anything silly and expect it to work.

API

tralloc_siz

size_t tralloc_siz();

Returns the number of bytes heap-allocated by tralloc memory allocation functions.

tralloc_limit

size_t tralloc_limit();

Returns the maximum limit set on tralloc_siz. If 0 is returned, there is no limit (returns 0 by default).

tralloc_setlimit

size_t tralloc_setlimit(size_t n);

Sets the maximum limit on tralloc_siz. If this limit is reached, then tralloc alloc functions will fail and return NULL. Returns n if successful and 0 if unsuccessful.

tralloc_allocsiz

size_t tralloc_allocsiz(void *ptr);

Returns number of bytes allocated for ptr.

ptr must be a the address returned by a tralloc allocation.

stdlib wrappers

These functions behave exactly the same and their stdlib counterparts. The only difference is that they will also add the memory overhead required to track the number of allocated bytes for each pointer (which sizeof(size_t) per-pointer) and increment/decrement the tracked heapsiz accordingly. This overhead is stored at index [-1] of the returned pointers and used by functions within the library for tracking the heapsiz.

tralloc_malloc

void *tralloc_malloc(size_t n);

tralloc_calloc

void *tralloc_calloc(size_t num, size_t n);

tralloc_realloc

void *tralloc_realloc(void *ptr, size_t n);

ptr must be a the address returned by a tralloc allocation.

tralloc_free

void tralloc_free(void *ptr);

ptr must be a the address returned by a tralloc allocation.

Authors

• gearsix