[Bug preprocessor/64220] New: gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[Bug preprocessor/64220] New: gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[cameron at tacklind dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

            Bug ID: 64220
           Summary: gcc preprocessor defines outside of the reserved
                    namespace: unix linux AVR
           Product: gcc
           Version: 4.9.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cameron at tacklind dot com

The preprocessor defines names outside of the reserved namespace.

Essentially, if I'm not mistaken, the following command should output nothing
# gcc -dM -E - < /dev/null | grep -v '^#define _[_A-Z]'

However, for historical reasons, the preprocessor defines things like "unix"
and "linux" or "AVR" (with avr-gcc). I'm sure other show up on other systems
that I have not tested.

This has been referenced slightly in #2069, but the solution there was to just
manually un-define (-U) the extra define. (Which I'll do if I have to)

This is also talked about briefly in the documentation where it suggest better
alternatives like __unix__ et al. It even says "The C standard requires that
all system-specific macros be part of the reserved namespace."

https://gcc.gnu.org/onlinedocs/cpp/System-specific-Predefined-Macros.html

Could these defines outside of the reserved namespace be removed? Or deprecated
now (if they aren't already?) and removed in 5.0?

Or are those defines here to stay for historical reasons?

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
What is wrong on this?  You are not requesting any strict conformance mode, and
with GNU extensions those are acceptable.  Retry with -std=c89, -std=c99,
-std=c11, -ansi or similar options, then those macros shouldn't be defined.

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2014-12-08
     Ever confirmed|0                           |1

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[cameron at tacklind dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

--- Comment #2 from Cameron Tacklind <cameron at tacklind dot com> ---
Ah, I had not seen a reference to the -std making a difference. You are right
that adding -std=c99 removes the extra define.

Of note, I'm finding it difficult to find where this behavior (the define being
in gnuXX and not cXX) is described in the documentation. (But I may just be
blind)

If this is a desired define behavior, then by all means leave it and please
close this as a "WONTFIX". I just wanted to bring this up, in particular,
because I want to use AVR in a project I'm working on and I had not seen a good
reason for its existence besides deprecated usage.

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/onlinedocs/gcc-4.9.2/cpp/System-specific-Predefined-Macros.html#System-specific-Predefined-Macros

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #3)
> https://gcc.gnu.org/onlinedocs/gcc-4.9.2/cpp/System-specific-Predefined-
> Macros.html#System-specific-Predefined-Macros

When the -ansi option, or any -std option that requests strict conformance, is
given to the compiler, all the system-specific predefined macros outside the
reserved namespace are suppressed. The parallel macros, inside the reserved
namespace, remain defined.

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[cameron at tacklind dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

--- Comment #5 from Cameron Tacklind <cameron at tacklind dot com> ---
Pardon my brevity. Yes, I'd seen that.

I was trying to comment on this list seemingly missing a reference to that
particular difference. Or that if it is listed, it is difficult to find.

https://gcc.gnu.org/onlinedocs/gcc/C-Extensions.html

By my main issue persists of extra defines being set outside of the reserved
namespace. If this is something that you do not want to change, I am fine with
that. If so, please close this indicating that you want this behavior.

[Bug preprocessor/64220] gcc preprocessor defines outside of the reserved namespace: unix linux AVR

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64220

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
                 CC|                            |gjl at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #6 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Confusion has been resolved with help of the documentation.