PR middle-end/95353 - spurious -Wstringop-overflow writing to a trailing array plus offset

Also resolves:
PR middle-end/92939 - missing -Wstringop-overflow on negative index from the end of array

gcc/ChangeLog:

	PR middle-end/95353
	PR middle-end/92939
	* builtins.c (inform_access): New function.
	(check_access): Call it.  Add argument.
	(addr_decl_size): Remove.
	(get_range): New function.
	(compute_objsize): New overload.  Only use compute_builtin_object_size
	with raw memory function.
	(check_memop_access): Pass new argument to compute_objsize and
	check_access.
	(expand_builtin_memchr, expand_builtin_strcat): Same.
	(expand_builtin_strcpy, expand_builtin_stpcpy_1): Same.
	(expand_builtin_stpncpy, check_strncat_sizes): Same.
	(expand_builtin_strncat, expand_builtin_strncpy): Same.
	(expand_builtin_memcmp): Same.
	* builtins.h (check_nul_terminated_array): Declare extern.
	(check_access): Add argument.
	(struct access_ref, struct access_data): New structs.
	* gimple-ssa-warn-restrict.c (clamp_offset): New helper.
	(builtin_access::overlap): Call it.
	* tree-object-size.c (decl_init_size): Declare extern.
	(addr_object_size): Correct offset computation.
	* tree-object-size.h (decl_init_size): Declare.
	* tree-ssa-strlen.c (handle_integral_assign): Remove a call
	to maybe_warn_overflow when assigning to an SSA_NAME.

gcc/testsuite/ChangeLog:

	PR middle-end/95353
	PR middle-end/92939
	* c-c++-common/Wstringop-truncation.c: Remove an xfail.
	* gcc.dg/Warray-bounds-46.c: Remove a bogus warning.
	* gcc.dg/Wrestrict-9.c: Disable -Wstringop-overflow.
	* gcc.dg/Wstringop-overflow-12.c: Remove xfails.
	* gcc.dg/Wstringop-overflow-28.c: Same.
	* gcc.dg/builtin-stringop-chk-4.c: Same.
	* gcc.dg/builtin-stringop-chk-5.c: Same.
	* gcc.dg/builtin-stringop-chk-8.c: Same.
	* gcc.dg/strlenopt-74.c: Avoid buffer overflow.
	* gcc.dg/Wstringop-overflow-34.c: New test.
	* gcc.dg/Wstringop-overflow-35.c: New test.
	* gcc.dg/Wstringop-overflow-36.c: New test.
	* gcc.dg/Wstringop-overflow-37.c: New test.
	* gcc.dg/Wstringop-overflow-38.c: New test.

1 files changed, 23 insertions, 25 deletions

diff --git a/gcc/gimple-ssa-warn-restrict.c b/gcc/gimple-ssa-warn-restrict.c
index 19d2ec0..512fc13 100644
--- a/gcc/gimple-ssa-warn-restrict.c
+++ b/gcc/gimple-ssa-warn-restrict.c
@@ -1274,6 +1274,27 @@ builtin_access::strcpy_overlap ()
   return generic_overlap ();
 }
 
+/* For a BASE of array type, clamp REFOFF to at most [0, BASE_SIZE]
+   if known, or [0, MAXOBJSIZE] otherwise.  */
+
+static void
+clamp_offset (tree base, offset_int refoff[2], offset_int maxobjsize)
+{
+  if (!base || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE)
+    return;
+
+  if (refoff[0] < 0 && refoff[1] >= 0)
+    refoff[0] = 0;
+
+  if (refoff[1] < refoff[0])
+    {
+      offset_int maxsize =  maxobjsize;
+      if (tree size = TYPE_SIZE_UNIT (TREE_TYPE (base)))
+	maxsize = wi::to_offset (size);
+
+      refoff[1] = wi::umin (refoff[1], maxsize);
+    }
+}
 
 /* Return true if DSTREF and SRCREF describe accesses that either overlap
    one another or that, in order not to overlap, would imply that the size
@@ -1312,35 +1333,12 @@ builtin_access::overlap ()
 
   /* If the base object is an array adjust the bounds of the offset
      to be non-negative and within the bounds of the array if possible.  */
-  if (dstref->base
-      && TREE_CODE (TREE_TYPE (dstref->base)) == ARRAY_TYPE)
-    {
-      if (acs.dstoff[0] < 0 && acs.dstoff[1] >= 0)
-	acs.dstoff[0] = 0;
-
-      if (acs.dstoff[1] < acs.dstoff[0])
-	{
-	  if (tree size = TYPE_SIZE_UNIT (TREE_TYPE (dstref->base)))
-	    acs.dstoff[1] = wi::umin (acs.dstoff[1], wi::to_offset (size));
-	  else
-	    acs.dstoff[1] = wi::umin (acs.dstoff[1], maxobjsize);
-	}
-    }
+  clamp_offset (dstref->base, acs.dstoff, maxobjsize);
 
   acs.srcoff[0] = srcref->offrange[0];
   acs.srcoff[1] = srcref->offrange[1];
 
-  if (srcref->base
-      && TREE_CODE (TREE_TYPE (srcref->base)) == ARRAY_TYPE)
-    {
-      if (acs.srcoff[0] < 0 && acs.srcoff[1] >= 0)
-	acs.srcoff[0] = 0;
-
-      if (tree size = TYPE_SIZE_UNIT (TREE_TYPE (srcref->base)))
-	acs.srcoff[1] = wi::umin (acs.srcoff[1], wi::to_offset (size));
-      else if (acs.srcoff[1] < acs.srcoff[0])
-	acs.srcoff[1] = wi::umin (acs.srcoff[1], maxobjsize);
-    }
+  clamp_offset (srcref->base, acs.srcoff, maxobjsize);
 
   /* When the upper bound of the offset is less than the lower bound
      the former is the result of a negative offset being represented