[Bug c++/115165] New: ICE on -ftime-report with module and c++2b

["porten at kde dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115165

            Bug ID: 115165
           Summary: ICE on -ftime-report with module and c++2b
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: porten at kde dot org
  Target Milestone: ---

Purely by accident, I ran into an ICE when using -ftime-report on a file
including a system header with a .gcm file of that header present. The scenario
appeared after an attempt to improve compilation speed.

timevar.cc line 490 performs gcc_assert (!tv->standalone).

Note 1: A combination of #include <x> with x.gcm present may be unsupported.

Note 2: The error goes away when compiling with c++2a or c++20 rather than
c++2b.

$ cat main.cpp
#include <iostream>
int main(int, char **) { std::cout; }

$ g++ -fmodules-ts -std=c++2b -x c++-system-header iostream

$ g++ -ftime-report -fmodules-ts -std=c++2b main.cpp
main.cpp: In destructor ‘std::__codecvt_abstract_base<_InternT, _ExternT,
_StateT>::~__codecvt_abstract_base() [with _InternT = char16_t; _ExternT =
char; _StateT = __mbstate_t]’:
main.cpp:2:31: internal compiler error: in start, at timevar.cc:490
    2 | int main(int, char **) { std::cout; }
      |                               ^~~~
0x74294d timer::start(timevar_id_t)
        /home/user/git/gcc/gcc/timevar.cc:490
0x74294d timer::start(timevar_id_t)
        /home/user/git/gcc/gcc/timevar.cc:481
0x74294d timevar_start(timevar_id_t)
        /home/user/git/gcc/gcc/timevar.cc:475
0x87b7ec lazy_load_pendings(tree_node*)
        /home/user/git/gcc/gcc/cp/module.cc:19470
0x881c48 maybe_lazily_declare
        /home/user/git/gcc/gcc/cp/name-lookup.cc:2002
0x881c48 get_class_binding(tree_node*, tree_node*, bool)
        /home/user/git/gcc/gcc/cp/name-lookup.cc:2038
0x9342fd lookup_field_r
        /home/user/git/gcc/gcc/cp/search.cc:1061
0x934c18 dfs_walk_all(tree_node*, tree_node* (*)(tree_node*, void*), tree_node*
(*)(tree_node*, void*), void*)
        /home/user/git/gcc/gcc/cp/search.cc:1507
0x934c18 lookup_member(tree_node*, tree_node*, int, bool, int,
access_failure_info*)
        /home/user/git/gcc/gcc/cp/search.cc:1216
0x9350d0 lookup_fnfields(tree_node*, tree_node*, int, int)
        /home/user/git/gcc/gcc/cp/search.cc:1426
0x773277 build_op_delete_call(tree_code, tree_node*, tree_node*, bool,
tree_node*, tree_node*, int)
        /home/user/git/gcc/gcc/cp/call.cc:7864
0x892372 build_delete_destructor_body
        /home/user/git/gcc/gcc/cp/optimize.cc:140
0x893738 maybe_clone_body(tree_node*)
        /home/user/git/gcc/gcc/cp/optimize.cc:610
0x85f01f post_load_processing
        /home/user/git/gcc/gcc/cp/module.cc:17758
0x877793 lazy_load_binding(unsigned int, tree_node*, tree_node*, binding_slot*)
        /home/user/git/gcc/gcc/cp/module.cc:19424
0x889b64 name_lookup::search_namespace_only(tree_node*)
        /home/user/git/gcc/gcc/cp/name-lookup.cc:920
0x889ca4 name_lookup::search_namespace(tree_node*)
        /home/user/git/gcc/gcc/cp/name-lookup.cc:1006
0x889f8f name_lookup::search_namespace(tree_node*)
        /home/user/git/gcc/gcc/cp/name-lookup.cc:1001
0x889f8f name_lookup::search_qualified(tree_node*, bool)
        /home/user/git/gcc/gcc/cp/name-lookup.cc:1067
0x88d161 qualified_namespace_lookup
        /home/user/git/gcc/gcc/cp/name-lookup.cc:7278
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

GCC was built with today's state of the releases/gcc-14 branch. 

$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/opt/gcc-14/libexec/gcc/x86_64-pc-linux-gnu/14.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /home/porten/git/gcc/configure --disable-multilib
--prefix=/opt/gcc-14 --enable-languages=c,c++ : (reconfigured)
/home/porten/git/gcc/configure --disable-multilib --prefix=/opt/gcc-14
--enable-languages=c,c++ : (reconfigured) /home/porten/git/gcc/configure
--disable-multilib --prefix=/opt/gcc-14 --enable-languages=c,c++,lto
--no-create --no-recursion
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.1.1 20240520 (GCC)