dyexe - Dual-Purpose Executable/Library for macOS

This project demonstrates creating a macOS executable that can also be loaded as a dynamic library.

How It Works

The binary is built as a Position Independent Executable (PIE) with exported symbols using C++:

• -fPIC: Position Independent Code
• -Wl,-export_dynamic: Export symbols for dynamic loading
• -Wl,-pie: Create a PIE executable
• __attribute__((visibility("default"))): Mark functions for export
• C++ std::chrono for timestamp initialization

Building

make

This creates binaries in the build/ directory:

• build/dyexe - The dual-purpose binary
• build/test_loader - A test program that loads dyexe as a library

Usage

As an Executable

The executable prints a Unix timestamp (seconds since epoch) to stdout:

build/dyexe
# Output: 1766845603

As a Dynamic Library

build/test_loader build/dyexe

Or programmatically in C:

void *handle = dlopen("./dyexe", RTLD_LAZY);
long long (*get_time)(void) = dlsym(handle, "dyexe_get_time");
long long timestamp = get_time();
dlclose(handle);

Testing

Run all tests:

make test

This runs:

1. Executable test (test_executable.sh): Spawns the executable, captures stdout, and verifies the timestamp is close to current time
2. Library test (test_loader):
   • Loads dyexe as a dynamic library
   • Calls dyexe_get_time() twice and verifies both calls return the same value
   • Verifies the timestamp is close to current time

Run individual tests:

# Test executable mode
./test_executable.sh build/dyexe

# Test library mode
build/test_loader build/dyexe

API Functions

• long long dyexe_get_time(void) - Returns Unix timestamp (seconds since epoch) initialized at program start

Clean Up

make clean