PR middle-end/91490 - bogus argument missing terminating nul warning on strlen of a flexible array member

gcc/c-family/ChangeLog:

	PR middle-end/91490
	* c-common.c (braced_list_to_string): Add argument and overload.
	Handle flexible length arrays and unions.

gcc/testsuite/ChangeLog:

	PR middle-end/91490
	* c-c++-common/Warray-bounds-7.c: New test.
	* gcc.dg/Warray-bounds-39.c: Expect either -Warray-bounds or
	-Wstringop-overflow.
	* gcc.dg/strlenopt-78.c: New test.

gcc/ChangeLog:

	PR middle-end/91490
	* builtins.c (c_strlen): Rename argument and introduce new local.
	Set no-warning bit on original argument.
	* expr.c (string_constant): Pass argument type to fold_ctor_reference.
	Fold empty and zero constructors into empty strings.
	* gimple-fold.c (fold_nonarray_ctor_reference): Return a STRING_CST
	for missing initializers.
	* tree.c (build_string_literal): Handle optional argument.
	* tree.h (build_string_literal): Add defaulted argument.
	* gimple-ssa-warn-restrict.c (maybe_diag_access_bounds): Check
	no-warning bit on original expression.

From-SVN: r274837

1 files changed, 13 insertions, 8 deletions

diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index d576b08..fcffb98 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -759,11 +759,13 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
       dest_align = get_pointer_alignment (dest);
       if (tree_fits_uhwi_p (len)
 	  && compare_tree_int (len, MOVE_MAX) <= 0
-	  /* ???  Don't transform copies from strings with known length this
-	     confuses the tree-ssa-strlen.c.  This doesn't handle
-	     the case in gcc.dg/strlenopt-8.c which is XFAILed for that
-	     reason.  */
-	  && !c_strlen (src, 2)
+	  /* FIXME: Don't transform copies from strings with known length.
+	     Until GCC 9 this prevented a case in gcc.dg/strlenopt-8.c
+	     from being handled, and the case was XFAILed for that reason.
+	     Now that it is handled and the XFAIL removed, as soon as other
+	     strlenopt tests that rely on it for passing are adjusted, this
+	     hack can be removed.  */
+	  && !c_strlen (src, 1)
 	  && !((tmp_str = c_getstr (src, &tmp_len)) != NULL
 	       && memchr (tmp_str, 0, tmp_len) == NULL))
 	{
@@ -6969,12 +6971,15 @@ fold_nonarray_ctor_reference (tree type, tree ctor,
 				      from_decl, suboff);
 	}
     }
-  /* Memory not explicitly mentioned in constructor is 0.  */
-  return type ? build_zero_cst (type) : NULL_TREE;
+
+  if (!type)
+    return NULL_TREE;
+
+  return build_zero_cst (type);
 }
 
 /* CTOR is value initializing memory.  Fold a reference of TYPE and
-   bit size POLY_SIZE to the memory at bit POLY_OFFSET.  When SIZE
+   bit size POLY_SIZE to the memory at bit POLY_OFFSET.  When POLY_SIZE
    is zero, attempt to fold a reference to the entire subobject
    which OFFSET refers to.  This is used when folding accesses to
    string members of aggregates.  When non-null, set *SUBOFF to