C Smartptr

Header-only library, adding Go-like defer and C++ smartptr-like auto-free to C!
Requires gcc (-std=gnu99 or higher)

Examples

• Basic malloc/free

int main() {
    smartptr void *ptr = malloc(10);
    // Yep, ptr will be auto freed!
}

• Custom cleanup functions

void user_destroy(User *user);

int main() {
    // You can specify custom destructors
    smartptr_func(user_destroy) User *my_user = user_create("Denloob");
}

• You can defer a function to run in the end of the scope

if (x == 1) {
    pthread_mutex_lock(&mutex);
    defer({ pthread_mutex_unlock(&mutex); });

    // Do something

    // Mutex unlocked in the end of the block
}

• You can also defer code blocks with the variables in the scope!

my_user = ...
defer({ printf("Bye %s!\n", my_user->name); });

• And if you wish, you can smartptr blocks too

smartptr_block({
    puts("Freeing...");
    free(*(void **)ptr); // <--- ptr is a pointer to my_num
}) int *my_num = malloc(sizeof(*my_num));

For more examples see examples directory. The macros are documented in the header file

Installation

Copy smartptr.h into your project and #include it. That's it! Make sure you are using gcc, although other compilers might work too.

QnA

Q: I compile with gcc but use clangd for static analysis. Will this library break clang?

A: You can easily allow the library to "do nothing" if it detects a non compatible compiler (like clang).
Thus clang (or any other compiler) analyzer will not break, and the gcc-compiled code will still work as intended.
To do this, open the header, and in the beginning, find

// If you wish, you may enable for clang or any other non-gnu compiler to completely
// ignore most* smartptr/defer statements. This can be useful for example if you
// are using it as an LSP (like clangd).
// * - non-special features like smartptr_func_ptr or smartptr will still work
#if (!defined(__GNUC__) || defined(__clang__))

#if 0
#define smartptr__setting_DO_NOTHING_SPECIAL
#else
#error "Unsupported compiler"
#endif

#endif

Now, switch the #if 0 to #if 1.
That's it!

Q: I am writing in a non-libc environment and stdlib/free breaks my compiling/linking

A: The easiest solution is to completely disable smartptr__free. Open the header and locate

// If you do not wish to have a macro `smartptr` that calls free
// (for example if you don't have libc, remove the following define)
#define smartptr__setting_SUPPORT_FREE

somewhere in the beginning of the file. Now simply remove the #define line and you are good to go!
All of the other smartptr and defer features will work as intended.

Contributing

Contributions are welcome! Open an Issue or a PR with your questions/suggestions.

License

C Smartptr is licensed under the MIT License. See LICENSE for more details.

Other info

Inspired by this proposal.