[Bug libstdc++/110944] New: std::variant & optional GDB representation is too verbose

[Bug libstdc++/110944] New: std::variant & optional GDB representation is too verbose

[sebastian.redl at getdesigned dot at]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

            Bug ID: 110944
           Summary: std::variant & optional GDB representation is too
                    verbose
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sebastian.redl at getdesigned dot at
  Target Milestone: ---

The key lines of the GDB visualizers for std::variant and std::optional look
like this:

return "%s [no contained value]" % self.typename

Note that this contains the full typename of the object.

We use lots of optionals of Boost.Units types, which have *huge* types. Here's
a small snippet of output when I attempt to print a value:

landing_mass_ =
std::optional<boost::units::quantity<boost::units::unit<boost::units::list<boost::units::dim<boost::units::mass_base_dimension,
boost::units::static_rational<1, 1> >, boost::units::dimensionless_type>,
boost::units::homogeneous_system<boost::units::list<boost::units::si::meter_base_unit,
boost::units::list<boost::units::scaled_base_unit<boost::units::cgs::gram_base_unit,
boost::units::scale<10, boost::units::static_rational<3, 1> > >,
boost::units::list<boost::units::si::second_base_unit,
boost::units::list<boost::units::si::ampere_base_unit,
boost::units::list<boost::units::si::kelvin_base_unit,
boost::units::list<boost::units::si::mole_base_unit,
boost::units::list<boost::units::si::candela_base_unit,
boost::units::list<boost::units::angle::radian_base_unit,
boost::units::list<boost::units::angle::steradian_base_unit,
boost::units::dimensionless_type> > > > > > > > > >, void>, double>> =
{[contained value] = 45359.237000000001}

Note that this is just one field of a struct with many fields (quite a few of
them optionals of unit types), and the value I'm printing is a vector of
multiple such structs, and the type is repeated for every single instance of an
optional.

It is, in short, not useful; in fact it makes the debug output completely
unusable.

Please just remove it. If I need to know the type of something, I can easily
look it up in the source code if I'm unsure about them. The debugger needs to
focus on runtime values, which I cannot look up.

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-08-08
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

--- Comment #1 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:701ce3c723623af13597c05df09a049c57c52fc0

commit r14-3451-g701ce3c723623af13597c05df09a049c57c52fc0
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Aug 22 14:26:51 2023 +0100

    libstdc++: Declutter std::optional and std:variant pretty printers
[PR110944]

    As the PR says, including the template arguments in the GDB output of
    these class templates can result in very long names, especially for
    std::variant. You can use 'whatis' or other GDB commands to get details
    of the type, we don't need to include it in the value.

    We could consider including the type if it's not too long, but I think
    consistency is better (and we already omit the template arguments for
    std::vector and other class templates).

    libstdc++-v3/ChangeLog:

            PR libstdc++/110944
            * python/libstdcxx/v6/printers.py (StdExpOptionalPrinter): Do
            not show template arguments.
            (StdVariantPrinter): Likewise.
            * testsuite/libstdc++-prettyprinters/compat.cc: Adjust expected
            output.
            * testsuite/libstdc++-prettyprinters/cxx17.cc: Likewise.
            * testsuite/libstdc++-prettyprinters/libfundts.cc: Likewise.

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk, thanks for the suggestion.

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:3a3d3d2361e3c44dad472a5a12318cba19b6e643

commit r13-8047-g3a3d3d2361e3c44dad472a5a12318cba19b6e643
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Aug 22 14:26:51 2023 +0100

    libstdc++: Declutter std::optional and std:variant pretty printers
[PR110944]

    As the PR says, including the template arguments in the GDB output of
    these class templates can result in very long names, especially for
    std::variant. You can use 'whatis' or other GDB commands to get details
    of the type, we don't need to include it in the value.

    We could consider including the type if it's not too long, but I think
    consistency is better (and we already omit the template arguments for
    std::vector and other class templates).

    libstdc++-v3/ChangeLog:

            PR libstdc++/110944
            * python/libstdcxx/v6/printers.py (StdExpOptionalPrinter): Do
            not show template arguments.
            (StdVariantPrinter): Likewise.
            * testsuite/libstdc++-prettyprinters/compat.cc: Adjust expected
            output.
            * testsuite/libstdc++-prettyprinters/cxx17.cc: Likewise.
            * testsuite/libstdc++-prettyprinters/libfundts.cc: Likewise.

    (cherry picked from commit 701ce3c723623af13597c05df09a049c57c52fc0)

[Bug libstdc++/110944] std::variant & optional GDB representation is too verbose

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110944

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|14.0                        |13.3

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I've backported this for 13.3 as well.