LD_PRELOAD scripting

preload.c

#!/usr/bin/tcc -run
#include <stdio.h>  // printf, perror, vsprintf
// injector
#include <stdlib.h> // setenv
#include <unistd.h> // execve
// hoooooks
#define __USE_GNU // man page says _GNU_SOURCE but is wrong lol
#include <dlfcn.h> // dlsym
#include <string.h> // strcmp
#include <curses.h>

int main(int ac, char** av) {
    if (getenv("LD_PRELOAD")) {
        static int (*fun)();
        fun = dlsym(RTLD_NEXT, __func__);
        fun(ac, av);
    } else {
            printf("%d\n", system("/usr/bin/tcc " __FILE__ " -ldl -lncursesw -shared -o lmao.so"));
            //             ^                      ^ lmao
            setenv("LD_PRELOAD", "lmao.so", 1);
            extern char** environ;
            int ret = execve("/usr/bin/vbindiff", av, environ);
            perror("wat");
    }
}

int __sprintf_chk(char* str, int flag, size_t strlen, const char* format, ...) {
    if (0 == strcmp(format, "%02X ")) {format = "%02x";}
  
    va_list args;
    va_start(args, format);
    int ret = vsprintf(str, format, args);
    va_end(args);

    return ret;
}

int waddnstr(WINDOW* win, const char* str, int n) {
    static int (*fun)();
    if (!fun) {fun = dlsym(RTLD_NEXT, __func__);}

    fun(win, str, n);
    if (2 == strlen(str)) {
        int val;
        scanf("%02x", val);
        wattr_set(win, val, val, NULL);
    }
}