fishhook

To dynamically rebind symbols in Mach-O binaries on iOS (simulator or device), add fishhook.h and fishhook.c to your project and use the rebind_symbols function.

To use it, you must:

1. Define function pointers to hold the original implementations (e.g., static int (*orig_close)(int);).
2. Create replacement functions that perform your desired logic and then call the original function pointer.
3. Call rebind_symbols with an array of struct rebinding and the count of rebindings.

#import <dlfcn.h>
#import <UIKit/UIKit.h>
#import "fishhook.h"

static int (*orig_close)(int);

int my_close(int fd) {
  printf("Calling real close(%d)\n", fd);
  return orig_close(fd);
}

int main(int argc, char * argv[])
{
  @autoreleasepool {
    // Rebind 'close' to 'my_close' and store the original in 'orig_close'
    rebind_symbols((struct rebinding[1]){{"close", my_close, (void *)&orig_close}}, 1);

    close(0);
    return 0;
  }
}