[Bug c++/94632] [10 Regression] canonical types differ for identical types since r10-7622-g12f55e030ed068d5
cvs-commit at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Sat Apr 18 10:55:58 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94632
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:f83adb68ed9cef1fbd4c16447eb4e89676df9f62
commit r10-7787-gf83adb68ed9cef1fbd4c16447eb4e89676df9f62
Author: Patrick Palka <ppalka@redhat.com>
Date: Sat Apr 18 06:22:21 2020 -0400
c++: spec_hasher::equal and PARM_DECLs [PR94632]
In the testcase below, during specialization of c<int>::d, we build two
identical specializations of the parameter type b<decltype(e)::k> -- one
when
substituting into c<int>::d's TYPE_ARG_TYPES and another when substituting
into
c<int>::d's DECL_ARGUMENTS.
We don't reuse the first specialization the second time around as a
consequence
of the fix for PR c++/56247 which made PARM_DECLs always compare different
from
one another during spec_hasher::equal. As a result, when looking up
existing
specializations of 'b', spec_hasher::equal considers the template argument
decltype(e')::k to be different from decltype(e'')::k, where e' and e'' are
the
result of two calls to tsubst_copy on the PARM_DECL e.
Since the two specializations are considered different due to the mentioned
fix,
their TYPE_CANONICAL points to themselves even though they are otherwise
identical types, and this triggers an ICE in
maybe_rebuild_function_decl_type
when comparing the TYPE_ARG_TYPES of c<int>::d to its DECL_ARGUMENTS.
This patch fixes this issue at the spec_hasher::equal level by ignoring the
'comparing_specializations' flag in cp_tree_equal whenever the
DECL_CONTEXTs of
the two parameters are identical. This seems to be a sufficient condition
to be
able to correctly compare PARM_DECLs structurally. (This also subsumes the
CONSTRAINT_VAR_P check since constraint variables all have empty, and
therefore
identical, DECL_CONTEXTs.)
gcc/cp/ChangeLog:
PR c++/94632
* tree.c (cp_tree_equal) <case PARM_DECL>: Ignore
comparing_specializations if the parameters' contexts are
identical.
gcc/testsuite/ChangeLog:
PR c++/94632
* g++.dg/template/canon-type-14.C: New test.
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