Is -fvia-C still needed?

Simon Marlow marlowsd at
Thu Sep 25 08:18:16 EDT 2008

Jason Dusek wrote:
>   Without GCC, how would we compile C extensions?

I'm not sure what you mean.  To answer the original question: yes, 
-fvia-C is almost redundant.  We took some steps in 6.10.1 to make 
-fvia-C behave in a way more consistent with -fasm (that I still need to 
document properly!), so -fvia-C no longer includes any header files when 
compiling the generated C code.

If you were using -fvia-C to call C functions defined as CPP macros via 
the FFI, then you can't do that any more in 6.10.1.  You have to write a 
C wrapper function and call that instead.

I think -fvia-C generates slightly faster code in some cases, but it 
might also generate slower code sometimes.  FWIW, we still use it for 
our binary distributions, but I haven't measured the difference it 
makes, if any.


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