RAII mutex pseudo in c

rmtx.c

#include <stdio.h>
#include <stdbool.h>
#include <assert.h>

typedef struct {
    int locked;
} mutex_t;

static void mutex_init(mutex_t *mtx) {
    mtx->locked = 0;
}

static void mutex_lock(mutex_t *mtx) {
    ++mtx->locked;
}

static void mutex_unlock(mutex_t *mtx) {
    --mtx->locked;
}

typedef struct {
    mutex_t *mtx;
    bool locked;
} raii_mutex_t;

static void raii_mutex_cleanup(raii_mutex_t *mtx) {
    if (mtx->locked)
        mutex_unlock(mtx->mtx);
}

static void raii_mutex_lock(raii_mutex_t *mtx) {
    if (mtx->locked)
        return;
    mutex_lock(mtx->mtx);
    mtx->locked = true;
}

static void raii_mutex_unlock(raii_mutex_t *mtx) {
    if (!mtx->locked)
        return;
    mutex_unlock(mtx->mtx);
    mtx->locked = false;
}

#define raii_mutex(_name, _mtx) raii_mutex_t _name __attribute__((cleanup(raii_mutex_cleanup))) = {.mtx = (_mtx), .locked = false}

static void foo(mutex_t *mtx) {
    raii_mutex(rmtx, mtx);
    raii_mutex_lock(&rmtx);
    assert(mtx->locked == true);
}

int main(int argc, char **argv)
{
    mutex_t mtx;

    mutex_init(&mtx);
    foo(&mtx);
    assert(mtx.locked == false);

    return 0;
}