[Bug c++/116681] [12/13 Regression] ICE: in start, at timevar.cc:491 with -ftime-report -std=c++20

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116681

--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Simon Martin
<simartin@gcc.gnu.org>:

https://gcc.gnu.org/g:73db20707fd60f303313fda3c9245a06037f312a

commit r13-9448-g73db20707fd60f303313fda3c9245a06037f312a
Author: Simon Martin <simon@nasilyan.com>
Date:   Mon Mar 24 08:25:07 2025 +0100

    c++: Don't mix timevar_start and auto_cond_timevar for TV_NAME_LOOKUP
[PR116681]

    We currently ICE upon the following testcase when using -ftime-report

    === cut here ===
    template < int> using __conditional_t = int;
    template < typename _Iter >
    concept random_access_iterator = requires { new _Iter; };
    template < typename _Iterator >
    struct reverse_iterator {
      using iterator_concept =
        __conditional_t< random_access_iterator< _Iterator>>;
    };
    void RemoveBottom() {
      int iter;
      for (reverse_iterator< int > iter;;)
          ;
    }
    === cut here ===

    The problem is that qualified_namespace_lookup does a plain start() of
    the TV_NAME_LOOKUP timer (that asserts that the timer is not already
    started). However this timer has already been cond_start()'d in the call
    stack - by pushdecl - so the assert fails.

    This patch simply ensures that we always conditionally start this timer
    (which is done in all other places that use it).

            PR c++/116681

    gcc/cp/ChangeLog:

            * name-lookup.cc (qualified_namespace_lookup): Use an
            auto_cond_timer instead of using timevar_start and timevar_stop.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-pr116681.C: New test.

    (cherry picked from commit 005f7176e0f457a1e1a7398ddcb4a4972da28c62)