defer.h File Reference

Cross-platform defer statement implementation for automatic resource cleanup. This header provides a 'defer' statement that executes code when the current scope exits, similar to Go's defer or other languages' scope guards. More...

#include <stddef.h>

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Detailed Description

Cross-platform defer statement implementation for automatic resource cleanup. This header provides a 'defer' statement that executes code when the current scope exits, similar to Go's defer or other languages' scope guards.

References:

• https://gustedt.wordpress.com/2025/01/06/simple-defer-ready-to-use/
• https://thephd.dev/c2y-the-defer-technical-specification-its-time-go-go-go
• https://gcc.gnu.org/onlinedocs/gccint/Trampolines.html
• https://github.com/moon-chilled/Defer/blob/master/defer.h

Compilation Instructions

C++: g++ main.cpp clang++ main.cpp cl main.cpp (MSVC) No special flags required - uses RAII with lambdas

C with GCC: gcc -fno-trampolines main.c Uses function descriptors (safe, no executable stack required)

Alternative for GCC 4.9+: gcc main.c Uses nested functions with auto storage class (safe, no trampolines)

C with Clang: clang -fblocks -lBlocksRuntime main.c Requires blocks runtime library

Install blocks runtime: Ubuntu/Debian: sudo apt-get install libblocksruntime-dev Arch Linux: sudo pacman -S libdispatch

C with MSVC: cl main.c Uses __try/__finally (no special flags required)

Usage Example

#include "defer.h"
#include <stdio.h>
#include <stdlib.h>
 
int main() {
    FILE *f = fopen("test.txt", "w");
    defer({ fclose(f); printf("File closed\n"); });
 
    void *ptr = malloc(100);
    defer({ free(ptr); printf("Memory freed\n"); });
 
    fprintf(f, "Hello, World!\n");
    // Cleanup happens automatically in reverse order
    return 0;
}

Definition in file defer.h.