chdir to the location of the .app bundle in C++ macOS application - c++

Question

I have packaged a macOS binary of an application which loads resources in a folder just outside of the .app bundle. The directory structure looks like
Foo/
Foo.app/
Contents/
...
resources/
I would like to change the working directory of the application to the parent directory Foo/, and this is what I have come up with so far.
#if defined(APPLE)
#include "CoreFoundation/CoreFoundation.h"
#include <unistd.h>
#include <libgen.h>
#endif
int main() {
#if defined(APPLE)
// macOS workaround for setting the working directory to the location of the .app
{
CFBundleRef bundle = CFBundleGetMainBundle();
CFURLRef bundleURL = CFBundleCopyBundleURL(bundle);
char path[PATH_MAX];
Boolean success = CFURLGetFileSystemRepresentation(bundleURL, TRUE, (UInt8 *)path, PATH_MAX);
assert(success);
CFRelease(bundleURL);
chdir(dirname(path));
}
#endif
...
}
This appears to work on macOS 10.7 and 10.10 (which is all I have to test on), but on 10.12, users have reported that resources are not loading, so I suspect that the above hack no longer works correctly.
Is there a better way of changing to the directory of the .app bundle that is being run?

Answer 1

Loading resources from outside of the app bundle is a security vulnerability. Apple has implemented app translocation (a.k.a. path randomization) in 10.12 to prevent it. Their recommended solution is to ship your app in a signed disk image. See here:
Starting in macOS 10.12, you can no longer provide external code or data alongside your code-signed app in a zip archive or unsigned disk image. An app distributed outside the Mac App Store runs from a randomized path when it is launched and so cannot access such external resources. To provide secure execution, code sign your disk image itself using the codesign tool, or distribute your app through the Mac App Store. For more information, see the updated revision to macOS Code Signing In Depth.

Answer 2

Here is another way to do it, but I haven't tested it yet on all the macOS versions. I hope this helps someone, but I'm not accepting it as an answer until I determine it's the best method.
#include <unistd.h> // for chdir
#include <libgen.h> // for dirname
#include <mach-o/dyld.h> // for _NSGetExecutablePath
#include <limits.h> // for PATH_MAX?
char path[PATH_MAX];
uint32_t pathLen = sizeof(path);
int err = _NSGetExecutablePath(path, &pathLen);
assert(!err);
// Switch to the directory of the actual binary
chdir(dirname(path));
// and then go up three directories to get to the folder of the .app bundle
chdir("../../../");