[Bug c++/84843] [8 Regression] C++ ICE on builtin redefinition since r258391

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84843

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jason at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The ICE is because of assertion that DECL_INITIAL is non-NULL; when
duplicate_decls is called, olddecl is the builtin from builtins.def with NULL
DECL_INITIAL, and newdecl is the user definition with error_mark_node as
DECL_INITIAL.  If the pedwarn errors, I guess we could return error_mark_node
instead of olddecl and the error-recovery would work fine, but for -fpermissive
I have no idea what to do, except for returning NULL_TREE, but that is
something you didn't like.