[Bug c++/115503] New: Explicit deduction guide - Capture parameter pack in lambda - Compiler segfaults

[Bug c++/115503] New: Explicit deduction guide - Capture parameter pack in lambda - Compiler segfaults

[thomaspkhealy at yahoo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115503

            Bug ID: 115503
           Summary: Explicit deduction guide - Capture parameter pack in
                    lambda - Compiler segfaults
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: thomaspkhealy at yahoo dot com
  Target Milestone: ---

With the trunk version of g++ (dated 15 June 2023), the following program
causes the compiler to segfault:

    template<unsigned>
    struct Frog {
        template<typename... Params>
        Frog(Params&&...){}
    };

    template<typename... Params>
    Frog(Params&&... args) -> Frog< sizeof([&args...](){}) >;

    int main(void)
    {
        Frog var(1.1, 2.2, 3.3, 4.4);
    }

Here's a godbolt: https://godbolt.org/z/495xrT1c3

Here's the compiler output:

<source>: In substitution of 'template<class ... Params> Frog(Params&& ...)->
Frog<sizeof (<lambda>)> [with Params = {double, double, double, double}]':
<source>:12:37:   required from here
   12 |         Frog var(1.1, 2.2, 3.3, 4.4 );
      |                                     ^
<source>:8:55: internal compiler error: Segmentation fault
    8 |     Frog(Params&&... args) -> Frog< sizeof([&args...](){}) >;
      |                                                       ^
0x26c86bc internal_error(char const*, ...)
        ???:0
0xcc3f7d tsubst_lambda_expr(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xcb4f11 tsubst_template_arg(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xcb7319 tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xcb28ba tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xcb2798 tsubst(tree_node*, tree_node*, int, tree_node*)
        ???:0
0xc98733 instantiate_template(tree_node*, tree_node*, int)
        ???:0
0xccbd15 fn_type_unification(tree_node*, tree_node*, tree_node*, tree_node*
const*, unsigned int, tree_node*, unification_kind_t, int, conversion**, bool,
bool)
        ???:0
0xa8eb19 perform_dguide_overload_resolution(tree_node*, vec<tree_node*, va_gc,
vl_embed> const*, int)
        ???:0
0xc8ed76 do_auto_deduction(tree_node*, tree_node*, tree_node*, int,
auto_deduction_context, tree_node*, int, tree_node*)
        ???:0
0xb533f1 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int,
cp_decomp*)
        ???:0
0xc6f13a c_parse_file()
        ???:0
0xdc5989 c_common_parse_file()
        ???:0
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.

[Bug c++/115503] Explicit deduction guide - Capture parameter pack in lambda - Compiler segfaults

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115503

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-valid-code
      Known to fail|                            |10.1.0, 11.1.0, 9.1.0
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-06-15

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed. Seems to be ICEing since lambda in unevaluated context support was
added.