64-bit breakdown

[Simon Marlow]

Jay Scott wrote:
> I have a MacBook (which is a Core 2 Duo) running Mac OS X 10.4. On this
> platform, gcc makes 32-bit executables by default, but if you give it -
> m64 it makes them 64-bit. I've tried it, and it works. gcc gives its
> version as "i686-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer,
> Inc. build 5367)"
> 
> But 64-bit doesn't work with my ghc installation (6.8.2 from the binary
> distribution on the downloads page). If I compile a "Hello World"
> program with -fvia-c -optc-m64, it fails, saying
> 
> --
> Warning: retaining unknown function `_siC_entry.eh' in output from C compiler
> Warning: retaining unknown function `_Main_main_entry.eh' in output from
> C compiler
> Warning: retaining unknown function `_ZCMain_main_entry.eh' in output
> from C compiler
> Prologue junk?: _siC_entry:
> LFB142:
>         subq    $8, %rsp
> LCFI0:
> --
> 
> I don't need to solve this, but I thought I should make sure it's known.

GHC is built up front to generate either 32-bit or 64-bit code, there's 
no way to change this for a given GHC build.  You should be able to 
install two versions of GHC side-by-side, but if you need to pass -m64 
to gcc to get it to generate 64-bit code, then you will need to invoke 
ghc with something like

   ghc -optc-m64 -opta-m64 -optl-m64 ...

Cheers,
	Simon