[Bug libstdc++/79147] New: Uselsss _GLIBCXX_PACKAGE_* macros in <bits/c++config.h>

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79147

            Bug ID: 79147
           Summary: Uselsss _GLIBCXX_PACKAGE_* macros in
                    <bits/c++config.h>
           Product: gcc
           Version: 6.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

The libstdc++ headers define these macros:

/* Define to the address where bug reports for this package should be sent. */
#define _GLIBCXX_PACKAGE_BUGREPORT ""

/* Define to the full name of this package. */
#define _GLIBCXX_PACKAGE_NAME "package-unused"

/* Define to the full name and version of this package. */
#define _GLIBCXX_PACKAGE_STRING "package-unused version-unused"

/* Define to the one symbol short name of this package. */
#define _GLIBCXX_PACKAGE_TARNAME "libstdc++"

/* Define to the version of this package. */
#define _GLIBCXX_PACKAGE__GLIBCXX_VERSION "version-unused"

These are all pretty useless, but the last one is particularly silly. It should
probably by _GLIBCXX_PACKAGE_VERSION, but the sed rule in include/Makefile.am
modifies it twice:

        sed -e 's/HAVE_/_GLIBCXX_HAVE_/g' \
            -e 's/PACKAGE/_GLIBCXX_PACKAGE/g' \
            -e 's/VERSION/_GLIBCXX_VERSION/g' \
            -e 's/WORDS_/_GLIBCXX_WORDS_/g' \
            -e 's/ICONV_CONST/_GLIBCXX_ICONV_CONST/g' \
            -e '/[       ]_GLIBCXX_LONG_DOUBLE_COMPAT[   ]/d' \
            < ${CONFIG_HEADER} >> $@ ;\

If we did s/PACKAGE_/_GLIBCXX_PACKAGE_/ instead then it would give a more
sensible result.

We should also consider replacing this whole thing with something based on
AX_PREFIX_CONFIG_H instead, so everything in the auto-generated config.h gets