On Fri, 25 Feb 2005 13:58:52 -0500, Wolfgang Thaller
During my ongoing research on "doing whatever I feel like", I discovered that using C++ libaries in GHCi (no problems with GHC) wasn't as pleasant as I had hoped. Apparently C++ sources requires to be linked with crtbegin.o and crtend.o (and others?) and I was wondering how to solve this nicely. Any hints or pointers would be greatly appreciated.
I think the files crtbegin.o and crtend.o are Linux-specific or maybe GNU-binutils-specific. Different platforms tend to have different strange requirements for C++ code.
Loading shared libraries that happen to be written in C++ into GHCi shouldn't be a problem (or is it? definitely works on Mac OS X). Loading C++ .o files is a different story.
Generally speaking, there are at least two things that set C++ .o files apart from "normal" C .o files:
*) static constructors/destructors
Sometimes there are pieces of code that expect to be called before main() or at program termination. The GHCi Linker doesn't support this, so some code may crash because things haven't been initialised properly.
*) multiple definitions
There is often some code in C++ header files (e.g. templates, inline functions, class members declared in the class declaration). These pieces of code are sometimes inlined, but sometimes they are not; in that case, gcc generates code for them in every .o file that uses them and counts on the linker to just include one version in the final executable. The GHCi linker will probably just abort and complain about multiply-defined symbols.
The above is just theory, there might be even more problems in practice :-( .
I've written a binding to a C++ library where I use a simple wrapper file to overcome the name mangling (extern "C" functions calling C++, nothing fancy). Is there a way to make that more GHCi friendly or should I explore other options? -- Friendly, Lemmih