re PR c/27184 (Wrong code with pointers to arrays and types and strict aliasing)

2006-08-13  Alexandre Oliva  <aoliva@redhat.com>
            Andrew Pinski  <pinskia@physics.uc.edu>

        PR c/27184
        * tree.c (build_array_type): Unify array types with
        unspecified index_type.
        * c-decl.c (grokdeclarator): Make sure we do not modify a
        unified incomplete array type.
        * c-typeck.c (store_init_value): Create distinct type before
        filling in the index type in an initializer from a compound
        literal.

        * c-decl.c (grokdeclarator): Remove code where we copy the
        array type over.

2006-08-13  Alexandre Oliva  <aoliva@redhat.com>

        PR c/27184
        * gcc.dg/torture/pr27184.c: New test


Co-Authored-By: Andrew Pinski <pinskia@physics.uc.edu>

From-SVN: r116116

6 files changed, 78 insertions, 20 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8777567..37fbac8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+2006-08-13  Alexandre Oliva  <aoliva@redhat.com>
+	    Andrew Pinski  <pinskia@physics.uc.edu>
+
+	PR c/27184
+	* tree.c (build_array_type): Unify array types with
+	unspecified index_type.
+	* c-decl.c (grokdeclarator): Make sure we do not modify a
+	unified incomplete array type.
+	* c-typeck.c (store_init_value): Create distinct type before
+	filling in the index type in an initializer from a compound
+	literal.
+
+	* c-decl.c (grokdeclarator): Remove code where we copy the
+	array type over.
+
 2006-08-13  Andrew Pinski  <pinskia@physics.uc.edu>
 
 	* tree-pass.h (TODO_update_ssa): Fix which bit is used to take
diff --git a/gcc/c-decl.c b/gcc/c-decl.c
index 9a0e747..21b10a6 100644
--- a/gcc/c-decl.c
+++ b/gcc/c-decl.c
@@ -4309,6 +4309,18 @@ grokdeclarator (const struct c_declarator *declarator,
 		    size_varies = 1;
 		  }
 	      }
+	    else if (decl_context == TYPENAME)
+	      {
+		if (array_parm_vla_unspec_p)
+		  {
+		    /* The error is printed elsewhere.  We use this to
+		       avoid messing up with incomplete array types of
+		       the same type, that would otherwise be modified
+		       below.  */
+		    itype = build_range_type (sizetype, size_zero_node,
+					      NULL_TREE);
+		  }
+	      }
 
 	     /* Complain about arrays of incomplete types.  */
 	    if (!COMPLETE_TYPE_P (type))
@@ -4317,12 +4329,23 @@ grokdeclarator (const struct c_declarator *declarator,
 		type = error_mark_node;
 	      }
 	    else
+	    /* When itype is NULL, a shared incomplete array type is
+	       returned for all array of a given type.  Elsewhere we
+	       make sure we don't complete that type before copying
+	       it, but here we want to make sure we don't ever
+	       modify the shared type, so we gcc_assert (itype)
+	       below.  */
 	      type = build_array_type (type, itype);
 
 	    if (type != error_mark_node)
 	      {
 		if (size_varies)
 		  {
+		    /* It is ok to modify type here even if itype is
+		       NULL: if size_varies, we're in a
+		       multi-dimentional array and the inner type has
+		       variable size, so the enclosing shared array type
+		       must too.  */
 		    if (size && TREE_CODE (size) == INTEGER_CST)
 		      type
 			= build_distinct_type_copy (TYPE_MAIN_VARIANT (type));
@@ -4334,11 +4357,13 @@ grokdeclarator (const struct c_declarator *declarator,
 		   zero.  */
 		if (size && integer_zerop (size))
 		  {
+		    gcc_assert (itype);
 		    TYPE_SIZE (type) = bitsize_zero_node;
 		    TYPE_SIZE_UNIT (type) = size_zero_node;
 		  }
 		if (array_parm_vla_unspec_p)
 		  {
+		    gcc_assert (itype);
 		    /* The type is complete.  C99 6.7.5.2p4  */
 		    TYPE_SIZE (type) = bitsize_zero_node;
 		    TYPE_SIZE_UNIT (type) = size_zero_node;
@@ -4497,21 +4522,6 @@ grokdeclarator (const struct c_declarator *declarator,
       return decl;
     }
 
-  /* Detect the case of an array type of unspecified size
-     which came, as such, direct from a typedef name.
-     We must copy the type, so that each identifier gets
-     a distinct type, so that each identifier's size can be
-     controlled separately by its own initializer.  */
-
-  if (type != 0 && typedef_type != 0
-      && TREE_CODE (type) == ARRAY_TYPE && TYPE_DOMAIN (type) == 0
-      && TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (typedef_type))
-    {
-      type = build_array_type (TREE_TYPE (type), 0);
-      if (size_varies)
-	C_TYPE_VARIABLE_SIZE (type) = 1;
-    }
-
   /* If this is a type name (such as, in a cast or sizeof),
      compute the type and return it now.  */
 
diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index ff27c97..506b60f 100644
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -4326,16 +4326,18 @@ store_init_value (tree decl, tree init)
 
       if (TREE_CODE (inside_init) == COMPOUND_LITERAL_EXPR)
 	{
-	  tree decl = COMPOUND_LITERAL_EXPR_DECL (inside_init);
+	  tree cldecl = COMPOUND_LITERAL_EXPR_DECL (inside_init);
 
-	  if (TYPE_DOMAIN (TREE_TYPE (decl)))
+	  if (TYPE_DOMAIN (TREE_TYPE (cldecl)))
 	    {
 	      /* For int foo[] = (int [3]){1}; we need to set array size
 		 now since later on array initializer will be just the
 		 brace enclosed list of the compound literal.  */
-	      TYPE_DOMAIN (type) = TYPE_DOMAIN (TREE_TYPE (decl));
+	      type = build_distinct_type_copy (TYPE_MAIN_VARIANT (type));
+	      TREE_TYPE (decl) = type;
+	      TYPE_DOMAIN (type) = TYPE_DOMAIN (TREE_TYPE (cldecl));
 	      layout_type (type);
-	      layout_decl (decl, 0);
+	      layout_decl (cldecl, 0);
 	    }
 	}
     }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f70afc7..de4f9e6 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-08-13  Alexandre Oliva  <aoliva@redhat.com>
+
+	PR c/27184
+	* gcc.dg/torture/pr27184.c: New test.
+
 2006-08-12  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.target/i386/pr27827.c: Only compile on ilp32 target.
diff --git a/gcc/testsuite/gcc.dg/torture/pr27184.c b/gcc/testsuite/gcc.dg/torture/pr27184.c
new file mode 100644
index 0000000..cfb6ed2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr27184.c
@@ -0,0 +1,22 @@
+/* Copyright 2006 Free Software Foundation */
+
+/* Make sure a and a1 alias each other.
+   Incomplete array types used to not be unified, which broke aliasing.  */
+
+/* { dg-do run } */
+
+typedef long atype[];
+typedef long atype1[];
+int NumSift (atype *a, atype1 *a1)
+{
+  (*a)[0] = 0;
+  (*a1)[0] = 1;
+  return (*a)[0];
+}
+int main(void)
+{
+  long a[2];
+  if (!NumSift(&a, &a))
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree.c b/gcc/tree.c
index efccfb1..f4e53ef 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -5158,7 +5158,11 @@ build_array_type (tree elt_type, tree index_type)
   
   if (index_type == 0)
     {
-      layout_type (t);
+      tree save = t;
+      hashcode = iterative_hash_object (TYPE_HASH (elt_type), hashcode);
+      t = type_hash_canon (hashcode, t);
+      if (save == t)
+	layout_type (t);
       return t;
     }