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Re: [PATCH] Call braced_list_to_string after array size is fixed


Hi,

this is a minor update to the previous version, which does no longer try
to fold the array initializer of VLAs, due to this initializer hitting
an assertion in my varasm patch, I believe it is certainly not worth the
risk to do that optimization with VLAs.

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


Thanks
Bernd.

On 08/17/18 14:01, Bernd Edlinger wrote:
> Hi,
> 
> Yes I know Martin will see this as a capital offense, but to my excuse I must say
> it only happened in self defense :-)
> 
> As my other patch series depends on STRNG_CSTs with certain properties, it got
> broken by the way the string constants are created now, due to the 71625 patch.
> 
> In order to be able to bootstrap my patch with current trunk, I had to move
> the point where the char array constructor is converted to a STRING_CST to the
> point directly after the array bounds are fixed, so that it is possible to create
> the string constant (with implicit NUL termination) like all other C strings, without
> making the array larger.
> 
> I added a test case for a crash with an invalid string intializer (in C++).
> and removed an xfail in the new test case string2.C.  This way the C++ diagnostics
> matches the state before 71625 was applied.
> 
> This does not fix the other problems with 71625, but I don't think they are related
> to the way the string constants are created, so there should be no conflict.
> 
> 
> Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
> Is it OK for trunk?
> 
> 
> Thanks
> Bernd.
c-family:
2018-08-17  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* c-common.c (braced_list_to_string): Remove eval parameter.
	Add some more checks.  Always create zero-terminated STRING_CST.
	* c-common.h (braced_list_to_string): Adjust prototype.

c:
2018-08-17  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* c-decl.c (finish_decl): Call braced_list_to_string here ...
	* c-parser.c (c_parser_declaration_or_fndef): ... instead of here.


cp:
2018-08-17  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* decl.c (eval_check_narrowing): Remove.
	(check_initializer): Move call to braced_list_to_string from here ...
	* typeck2.c (store_init_value): ... to here.
	(digest_init_r): Remove handing of signed/unsigned char strings.

testsuite:
2018-08-17  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* c-c++-common/array-init.c: New test.
	* g++.dg/init/string2.C: Remove xfail.


Index: gcc/c/c-decl.c
===================================================================
--- gcc/c/c-decl.c	(revision 263554)
+++ gcc/c/c-decl.c	(working copy)
@@ -5011,6 +5011,17 @@ finish_decl (tree decl, location_t init_
       relayout_decl (decl);
     }
 
+  if (TREE_CODE (type) == ARRAY_TYPE
+      && DECL_INITIAL (decl)
+      && TREE_CODE (DECL_INITIAL (decl)) == CONSTRUCTOR)
+    {
+      tree typ1 = TYPE_MAIN_VARIANT (TREE_TYPE (type));
+      if (typ1 == char_type_node
+	  || typ1 == signed_char_type_node
+	  || typ1 == unsigned_char_type_node)
+	DECL_INITIAL (decl) = braced_list_to_string (type, DECL_INITIAL (decl));
+    }
+
   if (VAR_P (decl))
     {
       if (init && TREE_CODE (init) == CONSTRUCTOR)
Index: gcc/c/c-parser.c
===================================================================
--- gcc/c/c-parser.c	(revision 263554)
+++ gcc/c/c-parser.c	(working copy)
@@ -2126,15 +2126,6 @@ c_parser_declaration_or_fndef (c_parser
 	      if (d != error_mark_node)
 		{
 		  maybe_warn_string_init (init_loc, TREE_TYPE (d), init);
-
-		  /* Try to convert a string CONSTRUCTOR into a STRING_CST.  */
-		  tree valtype = TREE_TYPE (init.value);
-		  if (TREE_CODE (init.value) == CONSTRUCTOR
-		      && TREE_CODE (valtype) == ARRAY_TYPE
-		      && TYPE_STRING_FLAG (TREE_TYPE (valtype)))
-		    if (tree str = braced_list_to_string (valtype, init.value))
-		      init.value = str;
-
 		  finish_decl (d, init_loc, init.value,
 			       init.original_type, asm_name);
 		}
Index: gcc/c-family/c-common.c
===================================================================
--- gcc/c-family/c-common.c	(revision 263554)
+++ gcc/c-family/c-common.c	(working copy)
@@ -8510,39 +8510,24 @@ maybe_add_include_fixit (rich_location *
 }
 
 /* Attempt to convert a braced array initializer list CTOR for array
-   TYPE into a STRING_CST for convenience and efficiency.  When non-null,
-   use EVAL to attempt to evalue constants (used by C++).  Return
-   the converted string on success or null on failure.  */
+   TYPE into a STRING_CST for convenience and efficiency.  Return
+   the converted string on success or the original ctor on failure.  */
 
 tree
-braced_list_to_string (tree type, tree ctor, tree (*eval)(tree, tree))
+braced_list_to_string (tree type, tree ctor)
 {
-  unsigned HOST_WIDE_INT nelts = CONSTRUCTOR_NELTS (ctor);
+  if (!tree_fits_uhwi_p (TYPE_SIZE_UNIT (type)))
+    return ctor;
 
   /* If the array has an explicit bound, use it to constrain the size
      of the string.  If it doesn't, be sure to create a string that's
      as long as implied by the index of the last zero specified via
      a designator, as in:
        const char a[] = { [7] = 0 };  */
-  unsigned HOST_WIDE_INT maxelts = HOST_WIDE_INT_M1U;
-  if (tree size = TYPE_SIZE_UNIT (type))
-    {
-      if (tree_fits_uhwi_p (size))
-	{
-	  maxelts = tree_to_uhwi (size);
-	  maxelts /= tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (type)));
-
-	  /* Avoid converting initializers for zero-length arrays.  */
-	  if (!maxelts)
-	    return NULL_TREE;
-	}
-    }
-  else if (!nelts)
-    /* Avoid handling the undefined/erroneous case of an empty
-       initializer for an arrays with unspecified bound.  */
-    return NULL_TREE;
+  unsigned HOST_WIDE_INT maxelts = tree_to_uhwi (TYPE_SIZE_UNIT (type));
+  maxelts /= tree_to_uhwi (TYPE_SIZE_UNIT (TREE_TYPE (type)));
 
-  tree eltype = TREE_TYPE (type);
+  unsigned HOST_WIDE_INT nelts = CONSTRUCTOR_NELTS (ctor);
 
   auto_vec<char> str;
   str.reserve (nelts + 1);
@@ -8552,19 +8537,21 @@ braced_list_to_string (tree type, tree c
 
   FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), i, index, value)
     {
-      unsigned HOST_WIDE_INT idx = index ? tree_to_uhwi (index) : i;
+      unsigned HOST_WIDE_INT idx = i;
+      if (index)
+	{
+	  if (!tree_fits_uhwi_p (index))
+	    return ctor;
+	  idx = tree_to_uhwi (index);
+	}
 
       /* auto_vec is limited to UINT_MAX elements.  */
       if (idx > UINT_MAX)
-	return NULL_TREE;
+	return ctor;
 
-      /* Attempt to evaluate constants.  */
-      if (eval)
-	value = eval (eltype, value);
-
-      /* Avoid non-constant initializers.  */
+     /* Avoid non-constant initializers.  */
      if (!tree_fits_shwi_p (value))
-	return NULL_TREE;
+	return ctor;
 
       /* Skip over embedded nuls except the last one (initializer
 	 elements are in ascending order of indices).  */
@@ -8572,11 +8559,14 @@ braced_list_to_string (tree type, tree c
       if (!val && i + 1 < nelts)
 	continue;
 
+      if (idx < str.length())
+	return ctor;
+
       /* Bail if the CTOR has a block of more than 256 embedded nuls
 	 due to implicitly initialized elements.  */
       unsigned nchars = (idx - str.length ()) + 1;
       if (nchars > 256)
-	return NULL_TREE;
+	return ctor;
 
       if (nchars > 1)
 	{
@@ -8585,17 +8575,15 @@ braced_list_to_string (tree type, tree c
 	}
 
       if (idx > maxelts)
-	return NULL_TREE;
+	return ctor;
 
       str.safe_insert (idx, val);
     }
 
-  if (!nelts)
-    /* Append a nul for the empty initializer { }.  */
-    str.safe_push (0);
+  /* Append a nul string termination.  */
+  str.safe_push (0);
 
-  /* Build a STRING_CST with the same type as the array, which
-     may be an array of unknown bound.  */
+  /* Build a STRING_CST with the same type as the array */
   tree res = build_string (str.length (), str.begin ());
   TREE_TYPE (res) = type;
   return res;
Index: gcc/c-family/c-common.h
===================================================================
--- gcc/c-family/c-common.h	(revision 263554)
+++ gcc/c-family/c-common.h	(working copy)
@@ -1331,7 +1331,7 @@ extern void maybe_add_include_fixit (ric
 extern void maybe_suggest_missing_token_insertion (rich_location *richloc,
 						   enum cpp_ttype token_type,
 						   location_t prev_token_loc);
-extern tree braced_list_to_string (tree, tree, tree (*)(tree, tree) = NULL);
+extern tree braced_list_to_string (tree, tree);
 
 #if CHECKING_P
 namespace selftest {
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 263554)
+++ gcc/cp/decl.c	(working copy)
@@ -6282,30 +6282,6 @@ build_aggr_init_full_exprs (tree decl, t
   return build_aggr_init (decl, init, flags, tf_warning_or_error);
 }
 
-/* Attempt to determine the constant VALUE of integral type and convert
-   it to TYPE, issuing narrowing warnings/errors as necessary.  Return
-   the constant result or null on failure.  Callback for
-   braced_list_to_string.  */
-
-static tree
-eval_check_narrowing (tree type, tree value)
-{
-  if (tree valtype = TREE_TYPE (value))
-    {
-      if (TREE_CODE (valtype) != INTEGER_TYPE)
-	return NULL_TREE;
-    }
-  else
-    return NULL_TREE;
-
-  value = scalar_constant_value (value);
-  if (!value)
-    return NULL_TREE;
-
-  check_narrowing (type, value, tf_warning_or_error);
-  return value;
-}
-
 /* Verify INIT (the initializer for DECL), and record the
    initialization in DECL_INITIAL, if appropriate.  CLEANUP is as for
    grok_reference_init.
@@ -6421,17 +6397,7 @@ check_initializer (tree decl, tree init,
 	    }
 	  else
 	    {
-	      /* Try to convert a string CONSTRUCTOR into a STRING_CST.  */
-	      tree valtype = TREE_TYPE (decl);
-	      if (TREE_CODE (valtype) == ARRAY_TYPE
-		  && TYPE_STRING_FLAG (TREE_TYPE (valtype))
-		  && BRACE_ENCLOSED_INITIALIZER_P (init))
-		if (tree str = braced_list_to_string (valtype, init,
-						      eval_check_narrowing))
-		  init = str;
-
-	      if (TREE_CODE (init) != STRING_CST)
-		init = reshape_init (type, init, tf_warning_or_error);
+	      init = reshape_init (type, init, tf_warning_or_error);
 	      flags |= LOOKUP_NO_NARROWING;
 	    }
 	}
Index: gcc/cp/typeck2.c
===================================================================
--- gcc/cp/typeck2.c	(revision 263554)
+++ gcc/cp/typeck2.c	(working copy)
@@ -813,6 +813,16 @@ store_init_value (tree decl, tree init, vec<tree,
     /* Digest the specified initializer into an expression.  */
     value = digest_init_flags (type, init, flags, tf_warning_or_error);
 
+  if (TREE_CODE (type) == ARRAY_TYPE
+      && TREE_CODE (value) == CONSTRUCTOR)
+    {
+      tree typ1 = TYPE_MAIN_VARIANT (TREE_TYPE (type));
+      if (typ1 == char_type_node
+	 || typ1 == signed_char_type_node
+	 || typ1 == unsigned_char_type_node)
+	value = braced_list_to_string (type, value);
+    }
+
   value = extend_ref_init_temps (decl, value, cleanups);
 
   /* In C++11 constant expression is a semantic, not syntactic, property.
@@ -1056,9 +1066,7 @@ digest_init_r (tree type, tree init, int
 
 	  if (TYPE_PRECISION (typ1) == BITS_PER_UNIT)
 	    {
-	      if (char_type != char_type_node
-		  && char_type != signed_char_type_node
-		  && char_type != unsigned_char_type_node)
+	      if (char_type != char_type_node)
 		{
 		  if (complain & tf_error)
 		    error_at (loc, "char-array initialized from wide string");
Index: gcc/testsuite/c-c++-common/array-init.c
===================================================================
--- gcc/testsuite/c-c++-common/array-init.c	(revision 0)
+++ gcc/testsuite/c-c++-common/array-init.c	(working copy)
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-prune-output "sorry, unimplemented: non-trivial designated initializers not supported" } */
+
+char x[] = { [-1] = 1, 2, 3 }; /* { dg-error "array index in initializer exceeds array bounds" "" { target c } } */
Index: gcc/testsuite/g++.dg/init/string2.C
===================================================================
--- gcc/testsuite/g++.dg/init/string2.C	(revision 263554)
+++ gcc/testsuite/g++.dg/init/string2.C	(working copy)
@@ -54,7 +54,7 @@ template <class T>
 int tmplen ()
 {
   static const T
-    a[] = { 1, 2, 333, 0 };         // { dg-warning "\\\[\(-Wnarrowing|-Woverflow\)" "" { target { ! c++98_only } } }
+    a[] = { 1, 2, 333, 0 };         // { dg-warning "\\\[\(-Wnarrowing|-Woverflow\)" }
   return __builtin_strlen (a);
 }
 

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