[Bug build/26183] New: GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[Bug build/26183] New: GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[bergner at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

            Bug ID: 26183
           Summary: GDB build fails with error: ‘class
                    std::basic_string_view<char>’ has no member named
                    ‘to_string’
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: bergner at linux dot ibm.com
  Target Milestone: ---

Building current gdb trunk source using a gcc trunk build from today, I'm
seeing the following build (powerpc64le-linux) error:

/home/bergner/binutils/binutils-gdb/gdb/ada-lang.c: In constructor
‘ada_lookup_name_info::ada_lookup_name_info(const lookup_name_info&)’:
/home/bergner/binutils/binutils-gdb/gdb/ada-lang.c:13556:50: error: ‘class
std::basic_string_view<char>’ has no member named ‘to_string’
13556 |    = user_name.substr (1, user_name.size () - 2).to_string ();
      |                                                  ^~~~~~~~~
/home/bergner/binutils/binutils-gdb/gdb/ada-lang.c:13559:50: error: ‘class
std::basic_string_view<char>’ has no member named ‘to_string’
13559 |    = user_name.substr (1, user_name.size () - 1).to_string ();
      |                                                  ^~~~~~~~~
/home/bergner/binutils/binutils-gdb/gdb/ada-lang.c:13578:33: error: ‘using
string_view = using string_view = class std::basic_string_view<char>’ {aka
‘class std::basic_string_view<char>’} has no member named ‘to_string’
13578 |      m_encoded_name = user_name.to_string ();
      |                                 ^~~~~~~~~
/home/bergner/binutils/binutils-gdb/gdb/ada-lang.c:13581:29: error: ‘using
string_view = using string_view = class std::basic_string_view<char>’ {aka
‘class std::basic_string_view<char>’} has no member named ‘to_string’
13581 |  m_encoded_name = user_name.to_string ();
      |                             ^~~~~~~~~
make: *** [Makefile:1610: ada-lang.o] Error 1

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[bergner at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Peter Bergner <bergner at linux dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |powerpc64le-linux
              Build|                            |powerpc64le-linux
               Host|                            |powerpc64le-linux

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tuliom at ascii dot art.br]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Tulio Magno Quites Machado Filho <tuliom at ascii dot art.br> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tuliom at ascii dot art.br

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[bergner at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Peter Bergner <bergner at linux dot ibm.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Peter Bergner <bergner at linux dot ibm.com> ---
Adding Tom to CC, since he added the to_string uses to gdb back in April
(commit e0802d59969).

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
The problem was latent before my patch.
I think the issue is that our string_view has to_string,
but C++ officially does not.
https://en.cppreference.com/w/cpp/string/basic_string_view

The gdb one was copied from libstdc++; I don't know if
this represents a local divergence (seems unlikely),
or if upstream / the standard changed.

Probably the solution is to change gdbsupport's string view
to have a "gdb::to_string" free function, then use that
instead.  When using the real string view, this can
simply use a string constructor.

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[bergner at linux dot ibm.com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #3 from Peter Bergner <bergner at linux dot ibm.com> ---
Maybe this libstdc++ change from June 12th?

https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=cd0b94e650a880b2ab04922e476aa28007277d5c

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #4 from Tom Tromey <tromey at sourceware dot org> ---
Sending a patch soon.

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
(In reply to Peter Bergner from comment #3)
> Maybe this libstdc++ change from June 12th?
> 
> https://gcc.gnu.org/git/?p=gcc.git;a=commit;
> h=cd0b94e650a880b2ab04922e476aa28007277d5c

That one doesn't seem quite like the one, since afaict
it doesn't change basic_string_view.

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[simark at simark dot ca]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Simon Marchi <simark at simark dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |simark at simark dot ca

--- Comment #6 from Simon Marchi <simark at simark dot ca> ---
Indeed, we copied

  ./libstdc++-v3/include/experimental/string_view

and not

  ./libstdc++-v3/include/std/string_view

The use of the experimental one came from this thread:

  https://sourceware.org/legacy-ml/gdb-patches/2018-04/msg00097.html

And was implemented in the final version of the patchset:

  https://sourceware.org/legacy-ml/gdb-patches/2018-04/msg00111.html

In hindsight, it probably wasn't a good idea.  I'll check to see if we can move
to a version based on std/string_view instead.

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #7 from Tom Tromey <tromey at sourceware dot org> ---
https://sourceware.org/pipermail/gdb-patches/2020-June/169963.html

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

--- Comment #8 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5ac588997c3c2d032d5d5145d9245eb37354c23b

commit 5ac588997c3c2d032d5d5145d9245eb37354c23b
Author: Tom Tromey <tromey@adacore.com>
Date:   Tue Jun 30 07:53:03 2020 -0600

    Do not define basic_string_view::to_string

    gdb's copy of basic_string_view includes a to_string method.  However,
    according to cppreference, this is not a method on the real
    std::basic_string_view:

    https://en.cppreference.com/w/cpp/string/basic_string_view

    This difference matters because gdb_string_view.h will use the
    standard implementation when built with a C++17 or later.  This caused
    PR build/26183.

    This patch fixes the problem by changing the method to be a standalone
    helper function, and then rewriting the uses.  Tested by rebuilding
    with a version of GCC that defaults to C++17.

    (Note that the build still is not clean; and also I noticed that the
    libstdc++ string_view forbids the use of nullptr ... I wonder if gdb
    violates that.)

    gdb/ChangeLog
    2020-06-30  Tom Tromey  <tromey@adacore.com>

            PR build/26183:
            * ada-lang.c (ada_lookup_name_info::ada_lookup_name_info): Use
            gdb::to_string.

    gdbsupport/ChangeLog
    2020-06-30  Tom Tromey  <tromey@adacore.com>

            PR build/26183:
            * gdb_string_view.h (basic_string_view::to_string): Remove.
            (gdb::to_string): New function.

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[Bug build/26183] GDB build fails with error: ‘class std::basic_string_view<char>’ has no member named ‘to_string’

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26183

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |10.1

--- Comment #9 from Tom Tromey <tromey at sourceware dot org> ---
Fixed.

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