[Bug preprocessor/65387] New: cpp -C emits extraneous comment header on every file

[Bug preprocessor/65387] New: cpp -C emits extraneous comment header on every file

[bugs at stellardeath dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65387

            Bug ID: 65387
           Summary: cpp -C emits extraneous comment header on every file
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: trivial
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bugs at stellardeath dot org

cpp is often (mis)used for non-C files, many Fortran projects for example
prefer to run a separate preprocessor step by invoking cpp by hand instead of
relying on the built-in preprocessing of the fortran compiler (don't ask why -
I don't understand it either).

In order not to mess up anything in the non-C file, cpp is usually invoked as

  cpp -C -P -traditional

The "-C" flag started to make problems in recent versions(?), as this now emits
a large comment header on every file:

#> echo "asd" | cpp -C -P
/* Copyright (C) 1991-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */
/* This header is separate from features.h so that the compiler can
   include it implicitly at the start of every compilation.  It must
   not itself include <features.h> or any other header that includes
   <features.h> because the implicit include comes before any feature
   test macros that may be defined in a source file before it first
   explicitly includes a system header.  GCC knows the name of this
   header in order to preinclude it.  */
/* glibc's intent is to support the IEC 559 math functionality, real
   and complex.  If the GCC (4.9 and later) predefined macros
   specifying compiler intent are available, use them to determine
   whether the overall intent is to support these features; otherwise,
   presume an older compiler has intent to support these features and
   define these macros by default.  */
/* wchar_t uses ISO/IEC 10646 (2nd ed., published 2011-03-15) /
   Unicode 6.0.  */
/* We do not support C11 <threads.h>.  */
asd


Would it be too much trouble to not include this extraneous header?

Kind regards,
  Lorenz

[Bug preprocessor/65387] [4.8/4.9/5 Regression] cpp -C emits extraneous comment header on every file

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65387

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-11
                 CC|                            |jsm28 at gcc dot gnu.org
   Target Milestone|---                         |4.8.5
            Summary|cpp -C emits extraneous     |[4.8/4.9/5 Regression] cpp
                   |comment header on every     |-C emits extraneous comment
                   |file                        |header on every file
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Heh.  Does this since 4.8.  This is from stdc-predef.h we forcefully include in
each translation unit.  You can use -nostdinc to restore original behavior.

Note that this bug will likely be closed as invalid/wontfix.  OTOH the included
comment says the file is LGPL which may have issues if it gets included in
sth statically linked?  I think we should change its license to BSD/MIT.

[Bug preprocessor/65387] [4.8/4.9/5 Regression] cpp -C emits extraneous comment header on every file

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65387

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Oh, in my case stdc-predef.h comes from glibc thus the license comment should
be directed there.  The GCC shipped stuff seems to have the runtime exception.

[Bug preprocessor/65387] [4.8/4.9/5 Regression] cpp -C emits extraneous comment header on every file

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65387

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
https://gcc.gnu.org/gcc-4.8/porting_to.html suggests to use -ffreestanding

Of course, the real fix for this and future issues arising from such mis-use is
to make libcpp more general and enable cpp to have a "Fortran mode" (-x
fortran) or even compile a Fortran version of cpp (fpp?). This would be a very
valuable contribution to GCC and gfortran and, technically, it should be not
very difficult:

https://gcc.gnu.org/wiki/GettingStarted#Basics:_Contributing_to_GCC_in_10_easy_steps
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide384

--- Comment #1 from Matthias Klose <doko at gcc dot gnu.org> ---
patch posted at
https://gcc.gnu.org/ml/gcc-patches/2015-03/msg00627.html

[Bug preprocessor/65387] [4.8/4.9/5 Regression] cpp -C emits extraneous comment header on every file

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65387

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

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Well, IMHO if you do not want comments or are not prepared to handle them, just
don't use -C.
Fortran these days has integrated preprocessor, I doubt fpp would be of any use
and you'd need to define how exactly should "fortran" preprocessing behave
(e.g. how it is different from assembly preprocessing).  Note that even -E
-xassembler-with-cpp preprocessing includes stdc-predef.h by default, you need
to use -nostdinc to avoid that.
In any case, not a bug IMHO.