dlopen from command-line arguments

dlopentest.c

/*! \file dlopentest.c
    Testing dlopen with user args from the command line.
    
    ** Remember to use libdl, -ldl when compiling. **
    \author Christopher Welborn
    \date   09-14-2019
*/
#include <dlfcn.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *concat_strings(const char *s1, const char *s2) {
    char *ret = malloc(strlen(s1) + strlen(s2) + 1);

    ret[0] = '\0';

    strcat(ret, s1);
    strcat(ret, s2);

    return ret;
}

static int open_library(char *libname) {
    char *tmp, *full_library_name;
    int ret;

    /* First, attempt to open just the library, if it has been fully
     * specified. */
    if (dlopen(libname, RTLD_NOW | RTLD_GLOBAL)) {
        printf("Loaded libary: %s\n", libname);
        return 1;
    }

    /* Append ".so" and prepend "lib" onto `libname' so that we accept
     * library names as GCC does. */
    tmp = concat_strings("lib", libname);
    full_library_name = concat_strings(tmp, ".so");
    printf("Couldn't load '%s', trying '%s'...\n", libname, full_library_name);
    if(dlopen(full_library_name, RTLD_NOW | RTLD_GLOBAL)) {
        printf("Library was loaded: '%s'\n", full_library_name);
        ret = 1;
    } else {
        printf("Library load failed: '%s'\n", full_library_name);
        ret = 0;
    }

    free(tmp);
    free(full_library_name);

    return ret;
}
int main(int argc, char** argv) {
    if (argc < 2) {
        fprintf(stderr, "No arguments. Usage: dlopentest FILE...\n");
        return EXIT_FAILURE;
    }
    for (int i = 1; i < argc; i++) {
        if (!open_library(argv[i])) continue;
    }
    return EXIT_SUCCESS;
}