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[PATCH] Fix the damage done by my other patch from yesterday to strlenopt-49.c


Hi,

this is how I would like to handle the over length strings issue in the C FE.
If the string constant is exactly the right length and ends in one explicit
NUL character, shorten it by one character.

I thought Martin would be working on it,  but as this is a really simple fix,
I would dare to send it to gcc-patches anyway, hope you don't mind...

The patch is relative to the other patch here: https://gcc.gnu.org/ml/gcc-patches/2018-07/msg01800.html


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


Thanks
Bernd.
gcc/c:
2018-07-30  Bernd Edlinger  <bernd.edlinger@hotmail.de>

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

testsuite:
2018-07-30  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* gcc.dg/strlenopt-49.c: Adjust test expectations.

diff -pur gcc/c/c-typeck.c gcc/c/c-typeck.c
--- gcc/c/c-typeck.c	2018-06-20 18:35:15.000000000 +0200
+++ gcc/c/c-typeck.c	2018-07-30 12:17:34.175481372 +0200
@@ -7435,29 +7435,38 @@ digest_init (location_t init_loc, tree t
 		}
 	    }
 
-	  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"));
-	      else if (warn_cxx_compat
-		       && compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
-		warning_at (init_loc, OPT_Wc___compat,
-			    ("initializer-string for array chars "
-			     "is too long for C++"));
+	      else if (compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
+		{
+		  if (warn_cxx_compat)
+		    warning_at (init_loc, OPT_Wc___compat,
+				("initializer-string for array chars "
+				 "is too long for C++"));
+		  if (len >= 2 * unit)
+		    {
+		      const char *p = TREE_STRING_POINTER (inside_init);
+
+		      len -= unit;
+		      if (memcmp (p + len - unit, "\0\0\0\0", unit) == 0)
+			inside_init = build_string (len, p);
+		    }
+		}
 	    }
 
+	  TREE_TYPE (inside_init) = type;
 	  return inside_init;
 	}
       else if (INTEGRAL_TYPE_P (typ1))
diff -pur gcc/testsuite/gcc.dg/strlenopt-49.c gcc/testsuite/gcc.dg/strlenopt-49.c
--- gcc/testsuite/gcc.dg/strlenopt-49.c	2018-07-30 13:02:34.735478726 +0200
+++ gcc/testsuite/gcc.dg/strlenopt-49.c	2018-07-30 13:08:21.074859303 +0200
@@ -11,9 +11,6 @@ const char a3[3] = "12\0";
 const char a8[8] = "1234567\0";
 const char a9[9] = "12345678\0";
 
-const char ax[9] = "12345678\0\0\0\0";   /* { dg-warning "initializer-string for array of chars is too long" } */
-const char ay[9] = "\00012345678\0\0\0\0";   /* { dg-warning "initializer-string for array of chars is too long" } */
-
 
 int len1 (void)
 {
@@ -27,27 +24,13 @@ int len (void)
   return len;
 }
 
-int lenx (void)
-{
-  size_t lenx = strlen (ax);
-  return lenx;
-}
-
-int leny (void)
-{
-  size_t leny = strlen (ay);
-  return leny;
-}
-
 int cmp88 (void)
 {
   int cmp88 = memcmp (a8, "1234567\0", sizeof a8);
   return cmp88;
 }
 
-/* { dg-final { scan-tree-dump-times "strlen" 0 "gimple" { xfail *-*-* } } }
-   { dg-final { scan-tree-dump-times "len0 = 0;" 1 "gimple" { xfail *-*-* } } }
-   { dg-final { scan-tree-dump-times "len = 18;" 1 "gimple" { xfail *-*-* } } }
-   { dg-final { scan-tree-dump-times "lenx = 8;" 1 "gimple" { xfail *-*-* } } }
-   { dg-final { scan-tree-dump-times "leny = 0;" 1 "gimple" { xfail *-*-* } } }
-   { dg-final { scan-tree-dump-times "cmp88 = 0;" 1 "gimple" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "strlen" 0 "gimple" } }
+   { dg-final { scan-tree-dump-times "len0 = 0;" 1 "gimple" } }
+   { dg-final { scan-tree-dump-times "len = 18;" 1 "gimple" } }
+   { dg-final { scan-tree-dump-times "cmp88 = 0;" 1 "gimple" } } */

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