Mail Archives: djgpp/1997/03/27/05:45:19
On Wed, 26 Mar 1997, Maurice Lombardi wrote:
> How can I know all options (including defaults) which have been used
> in the various libraries distributed in binary form (libc, libm,
> libgcc, libgpc etc.) in djdev201.zip, gcc2721b.zip and gpc20b.zip.
The Makefile and the auxiliary files it uses list them. Since the
Makefiles are used to build the library (nobody is crazy enough to
bypass the Makefiles and do it manually for the entire library), you
can be sure that these are the compiler options used.
> I have tried to compile libc, libm and others from djlsr201.zip.
> I have found bugs which indicate that the binaries have been compiled
> with another version of the compiler/assembler.
The only librray where this is known to happen is some old versions of
Allegro. Where did you see such problems in libc and libm?
> I execute my programs only on a Pentium or very seldom a 486,
> and I care only for speed, not for space or strange things like
> IEEE compliance or possibility to run with no coproc. and an emulator
> which cannot compute sin or cos (so I definitely want -ffast-math
> evereywhere including in the libraries).
It is of course OK to rebuild the library with options that are best
suited to your needs, especially if you don't distribute your code,
but please beware: when you use non-default options like -ffast-math
to compile general-purpose libraries such as libm.a, you might stumble
across bugs in the compiler or the library code that were never seen
in DJGPP. When you use the distributed libraries you at least have
the collective experience of many DJGPP users which made the libraries
relatively bug-free and stable. In my experience, the performance
gain is usually marginal, so I would suggest to recompile specific
single functions, and only if you have found that using non-default
options yields a significant improvements at run time.
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