re PR tree-optimization/79345 (passing yet-uninitialized member as argument to base class constructor should warn (-Wunitialized))

2017-03-02  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79345
	PR c++/42000
	* tree-ssa-alias.c (walk_aliased_vdefs_1): Take a limit
	param and abort the walk, returning -1 if it is hit.
	(walk_aliased_vdefs): Take a limit param and pass it on.
	* tree-ssa-alias.h (walk_aliased_vdefs): Add a limit param,
	defaulting to 0 and return a signed int.
	* tree-ssa-uninit.c (struct check_defs_data): New struct.
	(check_defs): New helper.
	(warn_uninitialized_vars): Use walk_aliased_vdefs to warn
	about uninitialized memory.

	* fixed-value.c (fixed_from_string): Use ulow/uhigh to avoid
	bogus uninitialized warning.
	(fixed_convert_from_real): Likewise.

	* g++.dg/warn/Wuninitialized-7.C: New testcase.
	* c-c++-common/ubsan/bounds-2.c: Add -Wno-uninitialized.
	* gcc.dg/uninit-pr19430-2.c: Add expected warning.

From-SVN: r245840