xcrun Error running program with custom malloc on macOS

Question

I am writing a custom malloc() - free() - realloc() set of functions for a school project.

I've written such functions and they appear to work, for example I can launch a simple program with my custom malloc and everithing works fine.

My malloc library is compiled as such ( gcc is symlinked to clang ):

# gcc -Wall -Wextra -Werror -shared -o libft_malloc_x86_64_Darwin.so ./src/malloc.o ./src/free.o ./src/realloc.o ./src/find.o ./src/alloc_mem.o ./src/show_alloc_mem.o ./src/utils.o -I ./include -I ./libft/include -I ./libft/libft -L./libft/ -L. -lft

Now, I tried to launch lldb with my malloc like this:

# ./run.sh lldb

with ./run.sh being:

#!/bin/sh
export DYLD_LIBRARY_PATH=.;
export DYLD_INSERT_LIBRARIES="libft_malloc.so";
export DYLD_FORCE_FLAT_NAMESPACE=1;
$@;

And I've got this error:

xcrun: error: unable to resolve xcrun_main (invalid handle passed to dlsym()).

What is this error about? I suppose this is a linker problem, but what this means exactly?

I've searched some info around, but nothing yet. Any tip is appreciated, as I will dig it.

I'm using macOS 10.12.6 and

# gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.0.0 (clang-900.0.38)
Target: x86_64-apple-darwin16.7.0
Thread model: posix

Answer 1

this error could happen when a function called from dynamic library does not exist. So, when you make export these variables, libc malloc will be replaced with yours. Do you implement all functions from this library?