Re: -isystem vs. #pragma system_header

[Zack Weinberg <zack at wolery dot cumb dot org>]

On Wed, May 17, 2000 at 06:48:40PM -0700, Nathan Myers wrote:
> (Cross-posted to libstdc++ list; please reply on the gcc list.)
> 
> In connexion with the new #pragma system_header...
> When last I checked (two years back), "-isystem" in C++ was 
> undocumented and severely broken in C++, doing what no sane 
> person could conceive of wanting.  If it hasn't been replaced 
> with something sane, maybe it would be best to get rid of it now.

I'm not able to divine from what you wrote, specifically what
semantics of -isystem you object to.  If it's just the implicit extern
"C", then I believe that is no longer done.

...
> I am concerned that with the new pragma it may become harder to control
> warning behavior on header files.  E.g., users don't ever want warnings 
> about system headers, but when we are developing we do want warnings.  
> Ideally, the headers would not have anything in them to warn about,
> but we have to sub-include vendor headers we have no control over.
> 
> This can be solved using something like the above suggested feature, or 
> by adding (yet) another "-W" option to control how the compiler emits
> warnings for system headers.

I could trivially add a -fno-system-headers or something like that
that shut off all special treatment for system headers.  Anything more
complex than that is going to need careful discussion.

zw