re PR c++/70621 (ICE on invalid code at -O1 and above on x86_64-linux-gnu in record_reference, at cgraphbuild.c:64)

/cp
2017-09-12  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/70621
	* decl.c (start_decl): Early return error_mark_node if duplicate_decls
	returns it; avoid misleading error message.

/testsuite
2017-09-12  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/70621
	* g++.dg/torture/pr70621.C: New.

From-SVN: r252040