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Date: Fri, 05 Jun 2015 09:57:11 +0300
From: "Eli Zaretskii (eliz AT gnu DOT org)" <djgpp AT delorie DOT com>
Subject: Re: DJGPP v2.05: some thoughts
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> Date: Thu, 04 Jun 2015 23:15:51 +0300
> From: "Andris Pavenis (andris DOT pavenis AT iki DOT fi)" <djgpp AT delorie DOT com>
> 
> echo '#include <iostream>' | i586-pc-msdosdjgpp-gcc -c -x c++ -std=c++11 - -o /dev/null
> 
> (hint: replace i586-pc-msdosdjgpp-gcc with simple gcc for native build)
> 
> Works OK with with -std=c++03, fails with -std=c++11 and -std=c++14
> 
> The problem is that our errno.h gets almost completely excluded
> 
> Andris
> 
> PS. following seems to workaround the problem:
> 
> Konsole output
> --- errno.h.orig        2015-06-04 23:12:46.745892048 +0300
> +++ errno.h     2015-06-04 23:13:13.382210708 +0300
> @@ -25,7 +25,7 @@
> 
> #endif /* (__STDC_VERSION__ >= 199901L) || !__STRICT_ANSI__ */
> 
> -#ifndef __STRICT_ANSI__
> +#if !defined(__STRICT_ANSI__) || defined(__cplusplus)
> 
> #define E2BIG          3
> #define EACCES         4

This looks wrong: we shouldn't have errno values visible under ANSI
compilation which are not defined by the ANSI C standard.  E.g., C99
only defines EDOM, EILSEQ, and ERANGE.

If the later standards define more errno values, they should be only
visible when the corresponding -std= option was specified for
compiler.  They should not be defined unconditionally, that is
definitely not TRT.

What preprocessor macros are defined by GCC that depend on -std=
value?  Assuming that it's __STDC_VERSION__, and that -stdc=c11 sets
it to 201112L and specifies that E2BIG should be in errno.h, then we
should do something like this:

 #if defined(__STRICT_ANSI__) && __STDC_VERSION__ >= 201112L
 #define E2BIG  3

However, the C11 draft standard I see still defines only the same 3
macros in errno that the old C99 standard did.  So I think this is a
C++ only thing, and we should also allow those values when __cplusplus
is defined, even under __STRICT_ANSI__.