re PR c++/81942 (ICE on empty constexpr constructor with C++14)

re PR c++/81942 (ICE on empty constexpr constructor with C++14)

/cp
2017-09-05  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81942
	* cp-tree.h (LABEL_DECL_CDTOR): Add and document.
	* decl.c (start_preparsed_function): Set LABEL_DECL_CDTOR when
	creating cdtor_label.
	* constexpr.c (returns): Add the case of a constructor/destructor
	returning via a LABEL_DECL_CDTOR label.
	(cxx_eval_constant_expression, case [GOTO_EXPR]): Likewise.

/testsuite
2017-09-05  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/81942
	* g++.dg/cpp1y/constexpr-return3.C: New.

From-SVN: r251714