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[PATCHv2] Handle overlength strings in the C FE


This is an alternative approach handle overlength strings in the C FE.

The difference to the previous version is that overlength
STRING_CST never have a longer TREE_STRING_LENGTH than the TYPE_DOMAIN.
And those STRING_CSTs are thus no longer zero terminated.

Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
Is it OK for trunk?

2018-08-01  Bernd Edlinger  <>

	* c-typeck.c (digest_init): Shorten overlength strings.

Index: gcc/c/c-typeck.c
--- gcc/c/c-typeck.c	(revision 263807)
+++ gcc/c/c-typeck.c	(working copy)
@@ -7488,19 +7488,17 @@ digest_init (location_t init_loc, tree type, tree
-	  TREE_TYPE (inside_init) = type;
 	  if (TYPE_DOMAIN (type) != NULL_TREE
 	      && TYPE_SIZE (type) != NULL_TREE
 	      && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST)
 	      unsigned HOST_WIDE_INT len = TREE_STRING_LENGTH (inside_init);
+	      unsigned unit = TYPE_PRECISION (typ1) / BITS_PER_UNIT;
 	      /* Subtract the size of a single (possibly wide) character
 		 because it's ok to ignore the terminating null char
 		 that is counted in the length of the constant.  */
-	      if (compare_tree_int (TYPE_SIZE_UNIT (type),
-				    (len - (TYPE_PRECISION (typ1)
-					    / BITS_PER_UNIT))) < 0)
+	      if (compare_tree_int (TYPE_SIZE_UNIT (type), len - unit) < 0)
 		pedwarn_init (init_loc, 0,
 			      ("initializer-string for array of chars "
 			       "is too long"));
@@ -7509,8 +7507,17 @@ digest_init (location_t init_loc, tree type, tree
 		warning_at (init_loc, OPT_Wc___compat,
 			    ("initializer-string for array chars "
 			     "is too long for C++"));
+	      if (compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
+		{
+		  unsigned HOST_WIDE_INT size
+		    = tree_to_uhwi (TYPE_SIZE_UNIT (type));
+		  const char *p = TREE_STRING_POINTER (inside_init);
+		  inside_init = build_string (size, p);
+		}
+	  TREE_TYPE (inside_init) = type;
 	  return inside_init;
       else if (INTEGRAL_TYPE_P (typ1))

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