[Bug c++/125498] [reflection] ICE with -g -freflection on constructor-parameter reflection NTTP

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125498

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:64627d4f8349af24f5a84c0936eb00256769b534

commit r17-1464-g64627d4f8349af24f5a84c0936eb00256769b534
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Jun 9 16:50:14 2026 -0400

    c++/reflection: ICE with -g on reflection of ctor param [PR125498]

    Here we ICE because S::S(int) lost its DECL_ARGUMENTS, and so the
    skip_artificial_parms_for in FUNCTION_FIRST_USER_PARM in write_reflection
    crashes on a null tree.   We've thrown away the body of S::S(int) in
    cgraph_node::release_body along with its DECL_ARGUMENTS:

          if (!keep_arguments)
            DECL_ARGUMENTS (decl) = NULL;

    This happens in finalize_compilation_unit -> analyze_functions because
    there are no cgraph_node::callers (so referred_to_p() is false I think),
    and .force_output is false.

    We then call mangle_decl from finalize_compilation_unit ->
    dwarf2out_early_finish.

    Instead of FUNCTION_FIRST_USER_PARM we can use DECL_PARM_INDEX, thus
    avoiding the need to either keep the body around or at least set
    keep_arguments.

            PR c++/125498

    gcc/cp/ChangeLog:

            * mangle.cc (write_reflection): Use DECL_PARM_INDEX for
            computing the parameter index.

    gcc/testsuite/ChangeLog:

            * g++.dg/reflect/mangle7.C: New test.
            * g++.dg/reflect/parameters_of9.C: New test.

    Reviewed-by: Patrick Palka <ppalka@redhat.com>