Re: [jamboost] -isystem and warnings

From: David Abrahams (dave_at_[hidden])
Date: 2002-10-27 22:49:18

Rene Rivera <grafik666_at_[hidden]> writes:

> [2002-10-27] David Abrahams wrote:
> 
> >
> >In some of my Boost.Build v2 testing I've encountered warnings from
> >GCC because we're normally using -isystem to add Boost headers as part
> >of the #include <...> -only search path (there appears to be no other
> >way). I'm beginning to think that we have to give up on -isystem,
> >since it causes so many problems, including that on some platforms it
> >adds an implicit extern "C" { } wrapper. For the record, I still think
> >we're doing the right thing by using angle-includes for boost.
> 
> That's fine for GCC, but if we switch to "-I" we'll probably get other
> warnings. 

I don't understand what you're saying. We'll get warnings with other
compilers if we switch GCC to use "-I" for <sysinclude>? You can't
mean _that_.

> Of course the reason it probably causes problems is that it
> doesn't seem to be a well tested part of GCC :-(

Yeah, it only gets used on ALL THE SYSTEM HEADERS! <wink>

> >Anyway, the warnings I've been seeing are:
> >
> > boost/cast.hpp:178: warning: decimal constant is so large that it is
> unsigned
> >
> >This one worries me a little. Has anyone tested the fencepost
> >condition here to make sure it's doing the right job?
> 
> I've seen that one but I was under the impression that it was not related at
> all to -isystem. 

I guess I wasn't clear. -isystem suppresses some warnings, including
the one above. Boost.Build v2 is just using -I so it shows up.

> I've seen that warning on the darwin-tools.jam file I've been trying
> to get working and it's using -I (as -isystem does the extern
> wrapping).
> 
> Are we getting warnings that go away if we don't use -isystem?

No, the other way around. We're not getting warnings that we'd see if
we were using -I.

-- 
David Abrahams
dave_at_[hidden] * http://www.boost-consulting.com