Re: Why Special float.h Files? (Was: Re: PATCH: XFAIL c99-float-1.c...)

[Richard Henderson <rth at redhat dot com>]

On Wed, Jan 31, 2001 at 08:01:37AM -0800, Jeffrey Oldham wrote:
> 1) How do we ensure that gcc's float.h are consistent with the
>    underlying system since the underlying system can change without
>    warning us?  Do I just guess correct values?

The underlying system *cannot* change -- <float.h> is like <limits.h>
(which we also provide) and describes the behaviour of the types that
the compiler uses to implement floating point operations.

> 2) Who uses these float.h header files?  gcc only?  gcc users?

Users.

> 3) Why are a proliferation of gcc/config/float-*.h files appearing
>    when the fixinc mechanism exists to modify existing system files
>    into a form that gcc needs?

There's no point.  We can just as well replace the whole thing
and avoid the weirdness fixinc is sure to run into.

>    Using this mechanism will help ensure
>    consistency between the system-provided files and what gcc needs.

You might as well ask how better to ensure how "size_t" remains
consistent with system-provided files.  The answer is the same:
that information is hard-coded into the compiler.

> 4) Where is documentation explaining these float-*.h files and which
>    gcc/config.gcc items to change? 

Guess.  There isn't any.

>    For example, only some of the
>    i[34567]86-*-* entries specify "float_format=i386" but I cannot
>    discern why some cases are omitted.

A mistake, for sure.


r~