Correct handling of indices into arrays with elements larger than 1 (PR c++/96511)

Resolves:
PR c++/96511 - Incorrect -Wplacement-new on POINTER_PLUS into an array with 4-byte elements
PR middle-end/96384 - bogus -Wstringop-overflow= storing into multidimensional array with index in range

gcc/ChangeLog:

	PR c++/96511
	PR middle-end/96384
	* builtins.c (get_range): Return full range of type when neither
	value nor its range is available.  Fail for ranges inverted due
	to the signedness of offsets.
	(compute_objsize): Handle more special array members.  Handle
	POINTER_PLUS_EXPR and VIEW_CONVERT_EXPR that come up in front end
	code.
	(access_ref::offset_bounded): Define new member function.
	* builtins.h (access_ref::eval): New data member.
	(access_ref::offset_bounded): New member function.
	(access_ref::offset_zero): New member function.
	(compute_objsize): Declare a new overload.
	* gimple-array-bounds.cc (array_bounds_checker::check_array_ref): Use
	enum special_array_member.
	* tree.c (component_ref_size): Use special_array_member.
	* tree.h (special_array_member): Define a new type.
	(component_ref_size): Change signature.

gcc/cp/ChangeLog:

	PR c++/96511
	PR middle-end/96384
	* init.c (warn_placement_new_too_small): Call builtin_objsize instead
	of duplicating what it does.

gcc/testsuite/ChangeLog:

	PR c++/96511
	PR middle-end/96384
	* g++.dg/init/strlen.C: Add expected warning.
	* g++.dg/warn/Wplacement-new-size-1.C: Relax warnings.
	* g++.dg/warn/Wplacement-new-size-2.C: Same.
	* g++.dg/warn/Wplacement-new-size-6.C: Same.
	* gcc.dg/Warray-bounds-58.c: Adjust
	* gcc.dg/Wstringop-overflow-37.c: Same.
	* g++.dg/warn/Wplacement-new-size-7.C: New test.

1 files changed, 16 insertions, 0 deletions

diff --git a/gcc/builtins.h b/gcc/builtins.h
index 72012a2..f226c63 100644
--- a/gcc/builtins.h
+++ b/gcc/builtins.h
@@ -173,6 +173,22 @@ struct access_ref
      For string functions the size of the actual access is
      further constrained by the length of the string.  */
   offset_int bndrng[2];
+
+  /* Return true if OFFRNG is the constant zero.  */
+  bool offset_zero () const
+  {
+    return offrng[0] == 0 && offrng[1] == 0;
+  }
+
+  /* Return true if OFFRNG is bounded to a subrange of possible offset
+     values.  */
+  bool offset_bounded () const;
+
+  /* Used to fold integer expressions when called from front ends.  */
+  tree (*eval)(tree);
+  /* Set if trailing one-element arrays should be treated as flexible
+     array members.  */
+  bool trail1special;
 };
 
 /* Describes a pair of references used in an access by built-in