HOWTO.md

Building

clang -shared -o /tmp/test-dylib.dylib test-dylib.c

Running

export DYLD_INSERT_LIBRARIES=/tmp/test-dylib.dylib
# test it
zsh -c 'echo Hello from zsh'

Sample output

# main is at: 0x10d74bdb8
Hello from zsh

test-dylib.c

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

static void init(void) __attribute__((constructor));
static void init(void)
{
    /* FIXME: this does only work if there's actually a symbol called 'main' */
    void *main_ptr = dlsym(RTLD_DEFAULT, "main");
    printf("main is at: %p\n", main_ptr);
}