Test dynamic library loading and (de-) initialisation

lib_loader.c

/*
 * Test program for https://github.com/nim-lang/Nim/issues/21403
 *
 * Build: make LDFLAGS="-ldl" CFLAGS="-g -O0" lib_loader
 * 
 * Run: heaptrack lib_loader libmylib.so [<iterations>]
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <dlfcn.h>

static int parse_loop_count(int argc, char** argv) {
    long loops = 100; // default
    if (argc >= 3) {
        char* end = NULL;
        loops = strtol(argv[2], &end, 10);
        if (end == argv[2] || *end != '\0' || loops <= 0 || loops > INT_MAX) {
            fprintf(stderr, "Invalid loop count '%s', using default 100\n", argv[2]);
            loops = 100;
        }
    }
    return (int)loops;
}

int main(int argc, char** argv) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s /path/to/library.so [loop_count]\n", argv[0]);
        return 1;
    }

    const char* lib_path = argv[1];
    int loops = parse_loop_count(argc, argv);

    printf("Running %d iterations...\n", loops);

    for (int i = 0; i < loops; ++i) {
        void* so = dlopen(lib_path, RTLD_NOW | RTLD_LOCAL);
        if (!so) {
            fprintf(stderr, "dlopen failed: %s\n", dlerror());
            return 2;
        }

        dlerror(); // Clear errors

        typedef void (*init_fn_t)(void);
        typedef void (*deinit_fn_t)(void);

        init_fn_t init_fn = (init_fn_t)dlsym(so, "dynlib_init");
        const char* err = dlerror();
        if (err || !init_fn) {
            fprintf(stderr, "dlsym('dynlib_init') failed: %s\n", err ? err : "symbol not found");
            dlclose(so);
            return 3;
        }

        dlerror();
        deinit_fn_t deinit_fn = (deinit_fn_t)dlsym(so, "dynlib_deinit");
        err = dlerror();
        if (err || !deinit_fn) {
            fprintf(stderr, "dlsym('dynlib_deinit') failed: %s\n", err ? err : "symbol not found");
            dlclose(so);
            return 4;
        }

        init_fn();
        deinit_fn();

        // Unload shared library
        dlclose(so);
    }

    return 0;
}