PR 23572 warnings for out of range floating-point constants

["Manuel López-Ibáñez" <lopezibanez at gmail dot com>]

:ADDPATCH c/c++:

At the moment, there is a warning if a floating-point constant is too
large to fit in the type's range. In such cases the constant is
converted to +inf or -inf. However, there is no warning if the
constant is too small and it is taken as 0. The following patch adds
such warning. It also adds the possibility of enabling the warning not
only with -pedantic but also with -Wconversion (since it fits its
definition).

Bootstrapped and regression tested with --enable-languages=all.

I could only test using i686-pc-linux-gnu. Any suggestions to make the
tests more portable?

OK for mainline?

2007-01-21  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>

 PR other/23572
 * c-lex.c (interpret_float): Warn if the constant is too small and
thus it is taken as 0. Warn with -pedantic or -Wconversion.

testsuite/
 * gcc.dg/gcc.dg/pr23572.c: New. Test with -pedantic
 * gcc.dg/gcc.dg/pr23572-2.c: New. Test with -pedantic-errors.
 * gcc.dg/gcc.dg/pr23572-3.c: New. Test with -Wconversion.

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