A portable, libre heap allocator replacement for malloc/free with built-in safety checks. Detects buffer overflows, double frees, invalid frees, and memory leaks.

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RealFCC 196a84947a leak: replace O(n) linked-list tracker with open-addressing hash table - alloc_tracker_t list + per-node sys_alloc replaced by a flat power-of-two slot table (leak_slot_t), grown geometrically - leak_tracker_add/remove now O(1) avg instead of O(n) scan + mmap per node - remove uses backward-shift deletion to keep probe chains short over long run times (no tombstone buildup) - new leak_tracker_update(ptr, size, file, line) collapses the remove+add pair used by realloc into a single in-place op - alloc.c: lr_realloc_debug uses leak_tracker_update at both grow-in-place and shrink-in-place paths - internal.h: add leak_tracker_update prototype No change to public API or leak report output format.		2026年06月30日 13:17:35 -05:00
docs	librealloc v1.0-rc1: portable heap allocator with safety features	2026年06月27日 17:51:15 -05:00
examples	Revert "Restructure allocator to glibc-style ptmalloc arena"	2026年06月30日 01:17:45 -05:00
include	Revert "Restructure allocator to glibc-style ptmalloc arena"	2026年06月30日 01:17:45 -05:00
src	leak: replace O(n) linked-list tracker with open-addressing hash table	2026年06月30日 13:17:35 -05:00
.gitignore	librealloc v1.0-rc1: portable heap allocator with safety features	2026年06月27日 17:51:15 -05:00
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README.md	chore: Fixed the docs	2026年06月28日 10:49:42 -05:00

README.md

librealloc

A portable, libre heap allocator replacement for malloc/free with built-in safety features. Designed for POSIX systems (Linux, macOS, BSD).

Features

Fast segregated free lists for near O(1) best-fit allocation
Thread-safe with pthread mutex protection
Buffer overflow detection via canaries on every block, crashes on corruption
Double-free detection with immediate abort and source location
Leak detection that crashes at exit if any allocations were not freed
Source tracking records file and line number for every allocation
No external dependencies beyond POSIX syscalls (mmap)
Portable across Linux (glibc, musl), macOS, and BSD

Documentation

Quick Start

make # Build library and example
make test # Build and run safety tests

Usage

#include "librealloc.h"
int main() {
 char *ptr = lr_malloc(100);
 strcpy(ptr, "Hello!");
 
 ptr = lr_realloc(ptr, 200);
 
 lr_free(ptr);
 return 0;
}

Link with: -llibrealloc -lpthread

API Reference

Allocation

Function	Description
`lr_malloc(size)`	Allocate `size` bytes. Records source file and line.
`lr_calloc(nmemb, size)`	Allocate zeroed memory. Checks for overflow.
`lr_realloc(ptr, size)`	Resize allocation. Copies existing data.
`lr_free(ptr)`	Free memory. Checks for errors, aborts on violation.

Diagnostics

Function	Description
`lr_alloc_dump_stats()`	Print allocation statistics to stdout.
`lr_alloc_check_integrity()`	Verify heap integrity.
`lr_alloc_verbose(enable)`	Enable verbose debug output to stderr.
`lr_force_leak_check()`	Manually trigger leak detection.
`lr_alloc_size(ptr)`	Return usable size of allocated block.
`lr_alloc_block_check(ptr)`	Verify canaries and magic on a block.

Safety Guarantees

Buffer overflow detection - Canaries before and after user data. Detected when the block is freed. Program aborts with file and line number.
Double-free prevention - Blocks track allocation state. Second free causes immediate abort with source location.
Invalid free detection - Magic number validation on every free. Stack pointers and garbage addresses are caught.
Memory leak detection - All allocations tracked. At exit, detailed report printed and program aborts.

Limitations

librealloc makes C code safer but cannot prevent:

Use-after-free through stale pointers
Dangling pointer aliases after freeing
Null pointer dereferences
Stack buffer overflows
Data races on shared data (only the allocator itself is thread-safe)

Performance

Segregated free lists with 12 size classes (32 bytes to 64KB). Coalescing on free reduces fragmentation. Per-block overhead is 64 bytes.

Platform Support

Linux (glibc, musl)
macOS
FreeBSD, OpenBSD, NetBSD

Windows is not supported.

Reporting Bugs

Bugs are tracked on Codeberg. When reporting a bug, please include:

Operating system and version
libc implementation (glibc, musl, etc.)
Compiler and version
Steps to reproduce the issue
Any relevant error messages or backtraces

Open an issue at: https://codeberg.org/RealFCC/librealloc/issues

Submitting Patches

See CONTRIBUTING.md for guidelines.

Pull requests: https://codeberg.org/RealFCC/librealloc/pulls

License

GNU Affero General Public License v3.0 or later. See LICENSE.md for the full text.