c++: prev declared hidden tmpl friend inst [PR112288]HEADtrunkmaster

When partially instantiating a previously declared hidden template
friend definition (at class template scope) such as slot_allocated in
the first testcase below, tsubst_friend_function needs to go through
all existing specializations thereof and make them point to the new
definition.

But when the previous declaration was also at class template scope,
old_decl is not the most general template, instead it's the partial
instantiation, and since instantiations are relative to the most general
template, old_decl's DECL_TEMPLATE_INSTANTIATIONS is empty.  So we
to consistently use the most general template here.  And when adjusting
DECL_TI_ARGS to match, only the innermost template arguments should be
preserved; the outer ones should correspond to the new definition.

Otherwise we fail a checking-only sanity check in instantiate_decl in
the first testcase, and in the second/third we end up emitting multiple
definitions of the template friend instantiation, resulting in a link
failure.

	PR c++/112288

gcc/cp/ChangeLog:

	* pt.cc (tsubst_friend_function): When adjusting existing
	specializations after defining a previously declared template
	friend, consider the most general template and correct
	DECL_TI_ARGS adjustment.

gcc/testsuite/ChangeLog:

	* g++.dg/template/friend80.C: New test.
	* g++.dg/template/friend81.C: New test.
	* g++.dg/template/friend81a.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

0 files changed, 0 insertions, 0 deletions