repl.c

// needs clang
// probably only macos
// usage:
// clang main.c && ./a.out
// try entering `5 * 5`, or `printf("hello\n")`

#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>

#include <unistd.h>

#include <sys/types.h>
#include <sys/wait.h>

#define MAX_LEN 1024

char *check_error() {
  char *err;    
  err = dlerror();
  if (err)
    {
      printf("dl error! %s\n", err);
    }
  
  return err;
}

int main(int argc, char **argv) {
  //  wat();
  char *plugin_name;
  void *plugin;
  int ( *f1ptr )();
  
  int res = 0;
  
  while (res != -1) {
    //  char lib[MAX_LEN];
    //  char func[MAX_LEN];
    char *lib;
    char *func;
    // char line[MAX_LEN];
    
    char *line = malloc(MAX_LEN);
    if (line == NULL) {
      printf("No memory\n");
      return 1;
    }
    
    /*
      printf("lib: ");  
      scanf("%s", lib);  
      printf("func: ");    
      scanf("%s", func);
    */
    
    lib = "aoeu.dylib";
    func = "aoeu";
    
    FILE *fp;
    fp = fopen("temp.c", "w+");
    
    printf("c=> ");    
    fgets(line, MAX_LEN, stdin);
    //scanf("%s", line);
    
    fputs("#include <stdio.h>\n", fp);
    fputs("int ", fp);
    fputs(func, fp);
    fputs("() {\n", fp);
    fputs("return ", fp);
    fputs(line, fp);
    fputs(";\n}", fp);
    fclose(fp);
    
    free(line);
    
    char * ls_args[7] = { "clang", "-shared", "-fpic", "temp.c", "-o", lib, NULL};
    pid_t c_pid, pid;
    int status;
    
    c_pid = fork(); //duplicate
    
    if( c_pid == 0 ){
      //child
      pid = getpid();
      
      //printf("Child: %d, %d: I'm the child\n", pid, c_pid);
      //printf("Child: sleeping for 2-seconds, then exiting with status 12\n");
      
      execvp( ls_args[0], ls_args );
    } else if (c_pid > 0) {
      //parent
      
      //waiting for child to terminate
      pid = wait(&status);
      
      if ( WIFEXITED(status) ){
        //printf("Parent: Child exited with status: %d\n", WEXITSTATUS(status));
      }
      
    }else{
      //error: The return of fork() is negative
      perror("fork failed");
      _exit(2); //exit failure, hard
    }
    
    check_error();
    
    plugin = dlopen(lib, RTLD_NOW);
    
    check_error();
    
    if (!plugin)
      {
        printf("Cannot load %s: %s", plugin_name, dlerror ());
      }
    
    f1ptr = dlsym( plugin, func );
    
    check_error();
    
    res = f1ptr();
    printf("%d\n", res);
    
    
    
    dlclose(plugin);
    
    check_error();
    
    
  }
  
  return 0;
}