Why am I getting "undefined reference to `dladdr'" even with -ldl for this simple program?

Question

I'm working through an LLVM Tutorial, but I'm having trouble compiling. I've written a minimal example that reproduces the issue:

#include "llvm/Module.h" #include "llvm/LLVMContext.h"  int main(int argc, char **argv) {     llvm::Module *module = new llvm::Module("test", llvm::getGlobalContext());     return 0; } 

When I try to compile, I get a bunch of 'undefined reference' erros:

clang++ `llvm-config --cxxflags`   -c -o test.o test.cpp clang++  test.o  `llvm-config --ldflags --libs core` -o test /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x6c): undefined reference to `dladdr' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Signals.o): In function `PrintStackTrace(void*)': (.text+0x1f6): undefined reference to `dladdr' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Mutex.o): In function `llvm::sys::MutexImpl::MutexImpl(bool)': (.text+0x53): undefined reference to `pthread_mutexattr_init' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Mutex.o): In function `llvm::sys::MutexImpl::MutexImpl(bool)': (.text+0x64): undefined reference to `pthread_mutexattr_settype' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Mutex.o): In function `llvm::sys::MutexImpl::MutexImpl(bool)': (.text+0x74): undefined reference to `pthread_mutexattr_setpshared' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Mutex.o): In function `llvm::sys::MutexImpl::MutexImpl(bool)': (.text+0x88): undefined reference to `pthread_mutexattr_destroy' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Mutex.o): In function `llvm::sys::MutexImpl::tryacquire()': (.text+0x179): undefined reference to `pthread_mutex_trylock' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::RWMutexImpl()': (.text+0x3e): undefined reference to `pthread_rwlock_init' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::~RWMutexImpl()': (.text+0x80): undefined reference to `pthread_rwlock_destroy' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::reader_acquire()': (.text+0xb9): undefined reference to `pthread_rwlock_rdlock' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::reader_release()': (.text+0xe9): undefined reference to `pthread_rwlock_unlock' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::writer_acquire()': (.text+0x119): undefined reference to `pthread_rwlock_wrlock' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(RWMutex.o): In function `llvm::sys::RWMutexImpl::writer_release()': (.text+0x149): undefined reference to `pthread_rwlock_unlock' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Threading.o): In function `llvm::llvm_execute_on_thread(void (*)(void*), void*, unsigned int)': (.text+0x1cc): undefined reference to `pthread_create' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Threading.o): In function `llvm::llvm_execute_on_thread(void (*)(void*), void*, unsigned int)': (.text+0x208): undefined reference to `pthread_attr_setstacksize' /usr/lib/llvm-2.9/lib/libLLVMSupport.a(Threading.o): In function `llvm::llvm_execute_on_thread(void (*)(void*), void*, unsigned int)': (.text+0x228): undefined reference to `pthread_join' clang: error: linker command failed with exit code 1 (use -v to see invocation) make: *** [test] Error 1 

If I view the manpage for dladdr, it says that I need to link with -ldl. But I'm already doing that with llvm-config:

$ llvm-config --ldflags --libs core -L/usr/lib/llvm-2.9/lib  -lpthread -lffi -ldl -lm  -lLLVMCore -lLLVMSupport -L/usr/lib/llvm-2.9/lib 

Additionally, -ldl appears in the correct order (i.e., after the .o file that requires the symbols).

I'm at a loss for the next step in debugging this issue. Can anyone point me in the right direction? I'm running LVVM 2.9-7 on Ubuntu 12.04.

Answer 1

The library requiring the symbols is included by -lLLVMSupport, so -ldl must come after -lLLVMSupport. I changed this:

`llvm-config --ldflags --libs core` 

To this:

`llvm-config --libs core` `llvm-config --ldflags` 

And the linker was successful.