[Bug libstdc++/40974] cannot build gcc-4.4.1: fenv_t has not been declared

["rwild at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #20 from rwild at gcc dot gnu dot org  2009-12-22 21:04 -------
Created an attachment (id=19374)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19374&action=view)
patch to turn off multiple inclusion guard for fenv.h C++ wrapper

Comment #18 confirms #13.

It is probably sufficient to turn off the inclusion guard for the include_next.
 However, it is also a slightly risky thing to do; and I'm
not quite sure whether it is conceptually the right thing to do.  (FWIW,
gnulib uses split inclusion guards for include_next in a number of places.)
(One risk is backward compatibility requirements stemming from including
the header from the installed, possibly older, compiler.)

Another strategy that comes to mind is to use -nostdinc++ and then add
the other include headers manually, but that is likely even more risky.

I'd be interested to see how the clfs build fares with this patch.  If
it succeeds, bonus points for also installing the just-built compiler
and then trying to do another cross build using the just-installed
compiler.

Building and testing of a native compiler succeeded on
x86_64-unknown-linux-gnu.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40974