Resize an APFS container on an iOS device

resize_apfs.c

//  clang -o resize_apfs -Wall -Wextra -Wpedantic -Werror -Wl,-U,_mh_execute_header,-e,_main -Xlinker APFS.tbd resize_apfs.c
//  Tested on iOS 10 and 15, won't work on iOS 12
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

typedef int (*apfs_resize_container_t)(const char *, unsigned long long);
typedef const char *(*apfs_get_error_string_t)(int);

int main(int argc, char *argv[]) {
    if (argc != 3) {
        printf("Usage: %s diskToResize newSize\n", argv[0]);
        return 1;
    }

    const char *diskToResize = argv[1];
    unsigned long long newSize = strtoull(argv[2], NULL, 10);

    void *apfsHandle = dlopen("/System/Library/PrivateFrameworks/APFS.framework/APFS", RTLD_LAZY);
    if (!apfsHandle) {
        printf("Error: Failed to load APFS framework.\n");
        return 1;
    }

    apfs_resize_container_t apfs_resize_container = (apfs_resize_container_t)dlsym(apfsHandle, "APFSContainerResize");
    if (!apfs_resize_container) {
        printf("Error: Failed to get symbol APFSContainerResize.\n");
        dlclose(apfsHandle);
        return 1;
    }

    apfs_get_error_string_t apfs_get_error_string = (apfs_get_error_string_t)dlsym(apfsHandle, "APFSGetErrorString");
    if (!apfs_get_error_string) {
        printf("Error: Failed to get symbol APFSGetErrorString.\n");
        dlclose(apfsHandle);
        return 1;
    }

    int ret = apfs_resize_container(diskToResize, newSize);
    if (ret != 0) {
        printf("Error: Failed to resize APFS container with error code %d: %s\n", ret, apfs_get_error_string(ret));
        dlclose(apfsHandle);
        return 1;
    }

    printf("APFS container %s has been resized to %llu bytes.\n", diskToResize, newSize);

    dlclose(apfsHandle);
    return 0;
}