[Bug libstdc++/99413] New: internal library headers are not header-unit ready

[Bug libstdc++/99413] New: internal library headers are not header-unit ready

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99413

            Bug ID: 99413
           Summary: internal library headers are not header-unit ready
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nathan at gcc dot gnu.org
  Target Milestone: ---

We're attempting to build the std library as a bunch of header-units.  The
include graph partitioner naturally discovers that internal headers from bits/
are included everywhere, and should therefore be header-units themselves.  But
several (many?, most?) are not stand alone, and expect their includer to have
included some necessary definitions.

The ones we've hit so far are[*]

bits/predefined_ops.h:153:9: error: '_GLIBCXX14_CONSTEXPR' does not name a type

bits/functional_hash.h:71:31: error: '__void_t' was not declared in this scope

bits/range_access.h:179:33: error: 'reverse_iterator' does not name a type

[*] for reasons we're stuck with gcc-9 era libstdc++.

[Bug libstdc++/99413] internal library headers are not header-unit ready

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99413

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-03-05
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
There are *many* such problems e.g.

/home/jwakely/gcc/11/include/c++/11.0.1/bits/stl_set.h:92:52: error: 'less' in
namespace 'std' does not name a template type
   92 |   template<typename _Key, typename _Compare = std::less<_Key>,
      |                                                    ^~~~

But in most cases the header is only included from exactly one place (in this
case, from <set>). Will they not be selected to be header units by your
selection criteria, and so can be ignored (at least for now)?

None of the bits/foo.tcc files are ever intended to be included from anywhere
except at the end of the corresponding bits/foo.h header. Do those ones need to
be fixed? Again, they are included in exactly one place (explicitly by design
here, rather than just how the library is arranged).

[Bug libstdc++/99413] internal library headers are not header-unit ready

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99413

--- Comment #2 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
Correct.  We're only picking headers that are either (a) user-facing or (b)
included from more than one place.

Specifically we're partitioning the include graph into a set of multi-reached
sub-graphs.

And we're maintaining a bad-list, which are the case reported here.

Hope that helps.

[Bug libstdc++/99413] internal library headers are not header-unit ready

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99413

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:47cca0288d06bd851e5801d13bbee7d9374b685d

commit r11-7604-g47cca0288d06bd851e5801d13bbee7d9374b685d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Mar 10 15:27:41 2021 +0000

    libstdc++: Fix headers that can't be used as header units [PR 99413]

    This adds missing includes to internal library headers which get
    included from more than one other header, so that they can be compiled
    as a stand-alone header unit.

    For existing use cases these includes are no-ops because they're already
    done by the header that includes these files. For compiling them as a
    header unit, this ensures that they include what they use.

    libstdc++-v3/ChangeLog:

            PR libstdc++/99413
            * include/bits/align.h: Include debug/assertions.h.
            * include/bits/codecvt.h: Include bits/c++config.h.
            * include/bits/enable_special_members.h: Likewise.
            * include/bits/erase_if.h: Likewise.
            * include/bits/functional_hash.h: Include <type_traits>.
            * include/bits/invoke.h: Include bits/move.h.
            * include/bits/ostream_insert.h: Include bits/exception_defines.h.
            * include/bits/parse_numbers.h: Include <type_traits>.
            * include/bits/predefined_ops.h: Include bits/c++config.h.
            * include/bits/range_access.h: Include bits/stl_iterator.h.
            * include/bits/stl_bvector.h: Do not include bits/stl_vector.h.
            * include/bits/stl_iterator.h: Include
bits/stl_iterator_base_types.h.
            * include/bits/stl_uninitialized.h: Include bits/stl_algobase.h.
            * include/bits/uniform_int_dist.h: Include bits/concept_check.h.
            * include/bits/unique_lock.h: Include bits/std_mutex.h.
            * include/debug/assertions.h: Include bits/c++config.h.

[Bug libstdc++/99413] internal library headers are not header-unit ready

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99413

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |11.0
             Status|NEW                         |RESOLVED

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for gcc-11.