Passing a gcc flag through makefile

Question

I am trying to build a pass using llvm and I have finished building llvm and its associated components. However, when I run make after following all the steps to build a pass including the makefile, I get the following

relocation R_X86_64_32 against `a local symbol' can not be used when making a shared object; recompile with -fPIC

After tyring to find a fix by googling the error message, I came to know that this is not specific to llvm. A few solutions suggested that I should use "--enable-shared" while running configure but that didn't help my case. Now I want to re-build llvm using fPIC, as the error says. But how do I do this using the makefile?

Answer 1

Looks like you could add the -fPIC (for position-independent code, something you want for a shared library that could be loaded at any address) by setting shell variables:

export CFLAGS="$CFLAGS -fPIC"
export CXXFLAGS="$CXXFLAGS -fPIC"

Looking at Makefile.rules, these will be picked up and used. Seems strange that it wasn't there to begin with.

EDIT:

Actually, reading more in the makefiles, I found this link to the LLVM Makefile Guide. From Makefile.rules, setting either SHARED_LIBRARY=1 or LOADABLE_MODULE=1 (which implies SHARED_LIBRARY) in Makefile will put -fPIC in the compiler flags.