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Date: Mon, 18 May 2015 21:56:20 +0300
From: "Eli Zaretskii (eliz AT gnu DOT org)" <djgpp AT delorie DOT com>
Subject: Re: ANNOUNCE: DJGPP 2.05 beta 1
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> Date: Mon, 18 May 2015 19:05:41 +0300
> From: "Andris Pavenis (andris DOT pavenis AT iki DOT fi)" <djgpp AT delorie DOT com>
> 
> On 05/18/2015 06:22 PM, Ozkan Sezer (sezeroz AT gmail DOT com) wrote:
> > On 5/18/15, Eli Zaretskii (eliz AT gnu DOT org) <djgpp AT delorie DOT com> wrote:
> >>> Date: Mon, 18 May 2015 16:06:19 +0300
> >>> From: "Ozkan Sezer (sezeroz AT gmail DOT com)" <djgpp AT delorie DOT com>
> >>>
> >>> The discussion is about we are pointing to gcc's headers directory
> >>> for allowed includes when building djgpp itself, whereas
> >>>
> >>> (i) we don't need that at all anymore (it was done only to work around
> >>> a gcc builtin problem and it got solved without needing this hack),
> >>>
> >>> (ii) we are building with -nostdinc which means we are self-
> >>> sufficient, and that hack is against this,
> >>>
> >>> (iii) since our DBL_MAX, etc are not compile time constants but symbols,
> >>> and gcc ones are, the binary output of several djgpp functions such as
> >>> strtod, etc, are different with and without gcc-headers hack.
> >>>
> >>> Those are the reasons I am against allowing gcc's headers in djgpp
> >>> build.
> >> AFAIR, -nostdinc means without library headers, but it does not
> >> preclude the headers that are internal to the compiler.

Actually, I think we use -nostdinc to make sure that the header files
come from the library being compiled, not from the installed
production environment.  IOW, if you have DJGPP v2.03 installed and
want to build a v2.05 library, you don't want to include, say, stdio.h
that came with v2.03.

Which means...

> >> [...]
> Including GCC own headers at first is expected behavior.

...that including GCC headers is fine, provided that it's needed.

But why is it needed?  Andris, you installed the change that added
that 2 years ago; do you remember what was the reason for that?

> There is however one other thing:
> 
> Unmodified GCC float.h does NOT include next float.h. See
> https://github.com/gcc-mirror/gcc/blob/master/gcc/ginclude/float.h
> 
> For example in my Linux installation  there is no float.h in /usr/include.
> 
> Including  next float.h is an additional hack. I modified GCC float.h and put there
> #ifdef __DJGPP__
> #include_next <float.h>
> #endif
> near the begin of GCC float.h. As far I verified there is no float.h in gcc-3.2, but it appears
> in gcc-3.3. The oldest 3.3 DJGPP port deleted/v2gnu/gcc331b.zip already includes DJGPP float.h
> in the begin.
> 
> I verified now that for MINGW cross-compiler (I have it installed) "#include_next <float.h>" is at end of GCC float.h.

In my native MinGW installation, there's no such include_next, FWIW.