G++ defining _GNU_SOURCE

[Joern Rennecke]

> 1. define CPLUSCPLUS_CPP_SPEC as "-D_GNU_SOURCE " + CPP_SPEC. Am I right to 
> assume that K&R doesn't support:
> 
> #define CPLUSPLUS_CPP_SPEC "-D_GNU_SOURCE " CPP_SPEC

Yes.

> ? Or is there a way to do this in K&R? Otherwise most of the stuff between 
> CPP_SPEC and CPLUSPLUS_CPP_SPEC has to be shared (like aix51.h does) and 
> this looks quite error prone to me.

You can put the stuff for CPP_SPEC into an extra_spec, which is then used
both by CPP_SPEC and CPLUSPLUS_CPP_SPEC.