Tripwire

Lightweight C memory debugging wrapper. Include the header and it transparently replaces standard allocation and memory functions via preprocessor macros.

No compiler flags, no linking extra libraries, no external tools.

Why Tripwire?

	Tripwire	ASan	Valgrind	Electric Fence
Setup	Copy two files	Compiler flag (-fsanitize=address)	External binary	Link library
Compiler support	Any C89+ compiler	GCC/Clang only	N/A (runtime)	GCC/Clang
Platform	Anywhere malloc works	Linux, macOS, some BSDs	Linux (best), macOS (limited)	Linux
Overhead	Minimal (sentinel bytes)	~2x slowdown, ~3x memory	~10-20x slowdown	One page per allocation
Leak detection	Yes (tripwire_report())	Yes	Yes	No
Buffer overflow	Yes (sentinel canaries)	Yes (shadow memory)	Yes	Yes (page guards)
Double free	Yes	Yes	Yes	No
Source location	File and line number	File, line, stack trace	Stack trace	Signal only
Integration	#include "tripwire.h"	Rebuild with flag	Run under valgrind	Link with -lefence

Use tripwire when you want quick, portable memory checks with zero setup cost -- especially in environments where ASan or Valgrind aren't available (embedded targets, unfamiliar toolchains, quick debugging sessions).

Use ASan/Valgrind when you need thorough instrumentation, stack traces, or are debugging production-grade software on a supported platform.

Installation

Copy tripwire.h and tripwire.c into your project:

# As a file copy
cp tripwire.h tripwire.c /path/to/your/project/

# Or as a git submodule
git submodule add https://github.com/phil-base/tripwire.git vendor/tripwire

Usage

Include tripwire.h after the standard headers in your source files, and compile with tripwire.c:

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

int main(void)
{
    char *buf = malloc(10);
    // use buf...
    free(buf);

    tripwire_report();  // print any leaks
    tripwire_cleanup(); // free all internal tracking state
    return 0;
}

cc -o myprogram myprogram.c tripwire.c

Or use the included Makefile to build and run the test suite:

make run

Example Output

Buffer overflow (sentinel corrupted):

SENTINEL 1 cracked in main.c at 23

memset size doesn't match allocation:

MEMSET mismatch: expected 32 got 64 in main.c at 25

Double free:

free(): DOUBLE FREE:: main.c: 30

Leak report from tripwire_report():

LEAK: 128 bytes at 0x600000000010 allocated in parser.c:42
LEAK: 64 bytes at 0x600000000120 allocated in parser.c:58
tripwire: 2 leak(s) detected

"SENTINEL 0" means the bytes before the allocation were corrupted (underflow). "SENTINEL 1" means the bytes after the allocation were corrupted (overflow).

Wrapped Functions

Standard call	Tripwire replacement
malloc(size)	Adds sentinels, tracks allocation
realloc(p, size)	Validates pointer, checks sentinels, re-wraps
calloc(n, size)	Tracked zero-initialized allocation
strdup(s)	Tracked string duplication
free(p)	Validates pointer, checks sentinels, detects double-free
memset(p, c, l)	Checks sentinels and size match
memcpy(d, s, l)	Checks sentinels and overflow
memmove(d, s, l)	Checks sentinels and overflow

Diagnostics

Function	Purpose
tripwire_report()	Print all unfreed allocations with file and line
tripwire_cleanup()	Free all internal tracking state (call after report)

Limitations

• Not thread-safe. The internal allocation list has no locking. Use tripwire in single-threaded programs or single-threaded test harnesses.
• Sentinel-based detection only. Tripwire uses 4-byte canary values before and after each allocation. It catches overwrites that hit these bytes but cannot detect arbitrary out-of-bounds access the way ASan's shadow memory can.
• No stack or global checking. Only heap allocations (malloc, calloc, realloc, strdup) are tracked. Stack buffer overflows and global variable issues are invisible to tripwire.
• memset size mismatch is a heuristic. Tripwire warns when the memset size differs from the allocation size. Partial memset on a buffer is valid C but will trigger a warning.
• Tracker metadata grows over the lifetime of the program. Freed allocation records are kept for double-free detection. Call tripwire_cleanup() at program exit to release them.

License

MIT. See LICENSE.