Re: gcc and profiling

[Marc Espie <Marc.Espie@liafa.jussieu.fr>]

The interfacing of gcc with external programs, such as ld, is one of the
scarier parts of gcc itself.

There are some knobs to automate some *limited* amount of profiling support,
specifically, -pg automatically links against libc_p instead of libc.

Other libraries do not follow suit.  This appears to be intentional: -lm says
`link against libm.a'. If it automatically became libm_p.a, there would
be no easy way left to link against some profiled libraries and some 
non-profiled libraries... 

The design guideline is that libraries you explicitly have to mention on
the command line you need to care about, gcc will handle its `default'
libraries (-lc, -lgcc...) automatically.

There is a huge nasty problem with g++ and libstdc++ currently: there is
no mechanism in gcc akin to the libc magic handling, that would change the
name of the standard C++ when profiling is used. (Fortran has a similar
problem).  The solution does involve rewriting a fairly large part of the
specs handling code... which is already special-cased all over the place,
and I don't have the time to do it right now.

(for those of you who build the egcs-snapshot port, this is the cause of
failure of all tests involving C++ and profiling).
-- 
	Marc Espie		
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