[Bug preprocessor/59566] New: [4.8 regression] g++ preprocessor output includes comments meant for GNU C Library files

[Bug preprocessor/59566] New: [4.8 regression] g++ preprocessor output includes comments meant for GNU C Library files

[gdlxn at us dot ibm.com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59566

            Bug ID: 59566
           Summary: [4.8 regression] g++ preprocessor output includes
                    comments meant for GNU C Library files
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gdlxn at us dot ibm.com

Created attachment 31484
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31484&action=edit
Example input and output files

I've found that g++ 4.8.x preprocessor output unexpectedly includes comments
meant for GNU C Library files.

To illustrate this problem, I ran the g++ preprocessor on test.hpp using as
follows

    g++ -C -E -o test-<gcc-version>.hpp -P test.hpp

With g++ 4.7.3, this generated the expected output file.  However, with g++
4.8.0, 4.8.1, and 4.8.2 the generated output file unexpectedly contained a
number of comments meant for GNU C Library files.

[Bug preprocessor/59566] [4.8/4.9 regression] g++ preprocessor output includes comments meant for GNU C Library files

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59566

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2013-12-20
   Target Milestone|---                         |4.8.3
            Summary|[4.8 regression] g++        |[4.8/4.9 regression] g++
                   |preprocessor output         |preprocessor output
                   |includes comments meant for |includes comments meant for
                   |GNU C Library files         |GNU C Library files
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
You are using -C, so what do you expect?  Note that since 4.8.x GCC
automatically
includes stdc-predef.h (which you can see when you remove the -P option).  The
comment nicely explains in the last sentence:

/* 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.  */

Thus, it works as designed. No?

[Bug preprocessor/59566] [4.8/4.9 regression] g++ preprocessor output includes comments meant for GNU C Library files

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59566

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

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

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Yeah, that is not a bug.
With -ffreestanding, -nostdinc or -fpreprocessed <stdc-predef.h> isn't
automatically included, but you then have to deal with the other effects of
those options.

[Bug preprocessor/59566] [4.8/4.9 regression] g++ preprocessor output includes comments meant for GNU C Library files

[gdlxn at us dot ibm.com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59566

--- Comment #3 from gdlxn at us dot ibm.com ---
Richard and Jakub - Thanks for the quick response and explanation.  I was able
to use the -nostdinc option to suppress the automatic inclusion of
<stdc-predef.h>, which eliminates the unwanted comments.