1 files changed, 194 insertions, 31 deletions

diff --git a/gcc/tree.c b/gcc/tree.c
index 741f7a2..3299b34 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -3089,6 +3089,25 @@ first_field (const_tree type)
   return t;
 }
 
+/* Returns the last FIELD_DECL in the TYPE_FIELDS of the RECORD_TYPE or
+   UNION_TYPE TYPE, or NULL_TREE if none.  */
+
+tree
+last_field (const_tree type)
+{
+  tree last = NULL_TREE;
+
+  for (tree fld = TYPE_FIELDS (type); fld; fld = TREE_CHAIN (fld))
+    {
+      if (TREE_CODE (fld) != FIELD_DECL)
+	continue;
+
+      last = fld;
+    }
+
+  return last;
+}
+
 /* Concatenate two chains of nodes (chained through TREE_CHAIN)
    by modifying the last node in chain 1 to point to chain 2.
    This is the Lisp primitive `nconc'.  */
@@ -13363,8 +13382,8 @@ array_ref_up_bound (tree exp)
   return NULL_TREE;
 }
 
-/* Returns true if REF is an array reference or a component reference
-   to an array at the end of a structure.
+/* Returns true if REF is an array reference, component reference,
+   or memory reference to an array at the end of a structure.
    If this is the case, the array may be allocated larger
    than its upper bound implies.  */
 
@@ -13382,6 +13401,28 @@ array_at_struct_end_p (tree ref)
   else if (TREE_CODE (ref) == COMPONENT_REF
 	   && TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 1))) == ARRAY_TYPE)
     atype = TREE_TYPE (TREE_OPERAND (ref, 1));
+  else if (TREE_CODE (ref) == MEM_REF)
+    {
+      tree arg = TREE_OPERAND (ref, 0);
+      if (TREE_CODE (arg) == ADDR_EXPR)
+	arg = TREE_OPERAND (arg, 0);
+      tree argtype = TREE_TYPE (arg);
+      if (TREE_CODE (argtype) == RECORD_TYPE)
+	{
+	  if (tree fld = last_field (argtype))
+	    {
+	      atype = TREE_TYPE (fld);
+	      if (TREE_CODE (atype) != ARRAY_TYPE)
+		return false;
+	      if (VAR_P (arg) && DECL_SIZE (fld))
+		return false;
+	    }
+	  else
+	    return false;
+	}
+      else
+	return false;
+    }
   else
     return false;
 
@@ -13498,33 +13539,72 @@ component_ref_field_offset (tree exp)
     return SUBSTITUTE_PLACEHOLDER_IN_EXPR (DECL_FIELD_OFFSET (field), exp);
 }
 
+/* Given the initializer INIT, return the initializer for the field
+   DECL if it exists, otherwise null.  Used to obtain the initializer
+   for a flexible array member and determine its size.  */
+
+static tree
+get_initializer_for (tree init, tree decl)
+{
+  STRIP_NOPS (init);
+
+  tree fld, fld_init;
+  unsigned HOST_WIDE_INT i;
+  FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (init), i, fld, fld_init)
+    {
+      if (decl == fld)
+	return fld_init;
+
+      if (TREE_CODE (fld) == CONSTRUCTOR)
+	{
+	  fld_init = get_initializer_for (fld_init, decl);
+	  if (fld_init)
+	    return fld_init;
+	}
+    }
+
+  return NULL_TREE;
+}
+
 /* Determines the size of the member referenced by the COMPONENT_REF
    REF, using its initializer expression if necessary in order to
    determine the size of an initialized flexible array member.
+   If non-null, *INTERIOR_ZERO_LENGTH is set when REF refers to
+   an interior zero-length array.
    Returns the size (which might be zero for an object with
    an uninitialized flexible array member) or null if the size
    cannot be determined.  */
 
 tree
-component_ref_size (tree ref)
+component_ref_size (tree ref, bool *interior_zero_length /* = NULL */)
 {
   gcc_assert (TREE_CODE (ref) == COMPONENT_REF);
 
+  bool int_0_len = false;
+  if (!interior_zero_length)
+    interior_zero_length = &int_0_len;
+
   tree member = TREE_OPERAND (ref, 1);
 
-  /* If the member is not an array, or is not last, or is an array with
-     more than one element, return its size.  Otherwise it's either
-     a bona fide flexible array member, or a zero-length array member,
-     or an array of length one treated as such.  */
-  tree size = DECL_SIZE_UNIT (member);
-  if (size)
+  tree memsize = DECL_SIZE_UNIT (member);
+  if (memsize)
     {
       tree memtype = TREE_TYPE (member);
-      if (TREE_CODE (memtype) != ARRAY_TYPE
-	  || !array_at_struct_end_p (ref))
-	return size;
+      if (TREE_CODE (memtype) != ARRAY_TYPE)
+	return memsize;
+
+      bool trailing = array_at_struct_end_p (ref);
+      bool zero_length = integer_zerop (memsize);
+      if (!trailing && (!interior_zero_length || !zero_length))
+	/* MEMBER is either an interior array or is an array with
+	   more than one element.  */
+	return memsize;
+
+      *interior_zero_length = zero_length && !trailing;
+      if (*interior_zero_length)
+	memsize = NULL_TREE;
 
-      if (!integer_zerop (size))
+      if (!zero_length)
 	if (tree dom = TYPE_DOMAIN (memtype))
 	  if (tree min = TYPE_MIN_VALUE (dom))
 	    if (tree max = TYPE_MAX_VALUE (dom))
@@ -13533,37 +13613,120 @@ component_ref_size (tree ref)
 		{
 		  offset_int minidx = wi::to_offset (min);
 		  offset_int maxidx = wi::to_offset (max);
-		  if (maxidx - minidx > 1)
-		    return size;
+		  if (maxidx - minidx > 0)
+		    /* MEMBER is an array with more than 1 element.  */
+		    return memsize;
 		}
     }
 
+  /* MEMBER is either a bona fide flexible array member, or a zero-length
+     array member, or an array of length one treated as such.  */
+
   /* If the reference is to a declared object and the member a true
      flexible array, try to determine its size from its initializer.  */
-  poly_int64 off = 0;
-  tree base = get_addr_base_and_unit_offset (ref, &off);
+  poly_int64 baseoff = 0;
+  tree base = get_addr_base_and_unit_offset (ref, &baseoff);
   if (!base || !VAR_P (base))
-    return NULL_TREE;
+    {
+      if (!*interior_zero_length)
+	return NULL_TREE;
 
-  /* The size of any member of a declared object other than a flexible
-     array member is that obtained above.  */
-  if (size)
-    return size;
+      if (TREE_CODE (TREE_OPERAND (ref, 0)) != COMPONENT_REF)
+	return NULL_TREE;
 
-  if (tree init = DECL_INITIAL (base))
-    if (TREE_CODE (init) == CONSTRUCTOR)
-      {
-	off <<= LOG2_BITS_PER_UNIT;
-	init = fold_ctor_reference (NULL_TREE, init, off, 0, base);
-	if (init)
-	  return TYPE_SIZE_UNIT (TREE_TYPE (init));
-      }
+      base = TREE_OPERAND (ref, 0);
+      baseoff = tree_to_poly_int64 (byte_position (TREE_OPERAND (ref, 1)));
+    }
+
+  /* BASE is the declared object of which MEMBER is either a member
+     or that is is cast to REFTYPE (e.g., a char buffer used to store
+     a REFTYPE object).  */
+  tree reftype = TREE_TYPE (TREE_OPERAND (ref, 0));
+  tree basetype = TREE_TYPE (base);
+
+  /* Determine the base type of the referenced object.  If it's
+     the same as REFTYPE and MEMBER has a known size, return it.  */
+  tree bt = basetype;
+  if (!*interior_zero_length)
+    while (TREE_CODE (bt) == ARRAY_TYPE)
+      bt = TREE_TYPE (bt);
+  bool typematch = useless_type_conversion_p (reftype, bt);
+  if (memsize && typematch)
+    return memsize;
+
+  memsize = NULL_TREE;
+
+  /* MEMBER is a true flexible array member.  Compute its size from
+     the initializer of the BASE object if it has one.  */
+  if (tree init = DECL_P (base) ? DECL_INITIAL (base) : NULL_TREE)
+    {
+      init = get_initializer_for (init, member);
+      if (init)
+	{
+	  memsize = TYPE_SIZE_UNIT (TREE_TYPE (init));
+	  if (tree refsize = TYPE_SIZE_UNIT (reftype))
+	    {
+	      /* Use the larger of the initializer size and the tail
+		 padding in the enclosing struct.  */
+	      poly_int64 rsz = tree_to_poly_int64 (refsize);
+	      rsz -= baseoff;
+	      if (known_lt (tree_to_poly_int64 (memsize), rsz))
+		memsize = wide_int_to_tree (TREE_TYPE (memsize), rsz);
+	    }
+
+	  baseoff = 0;
+	}
+    }
+
+  if (!memsize)
+    {
+      if (typematch)
+	{
+	  if (DECL_P (base)
+	      && DECL_EXTERNAL (base)
+	      && bt == basetype
+	      && !*interior_zero_length)
+	    /* The size of a flexible array member of an extern struct
+	       with no initializer cannot be determined (it's defined
+	       in another translation unit and can have an initializer
+	       witth an arbitrary number of elements).  */
+	    return NULL_TREE;
+
+	  /* Use the size of the base struct or, for interior zero-length
+	     arrays, the size of the enclosing type.  */
+	  memsize = TYPE_SIZE_UNIT (bt);
+	}
+      else
+	/* Use the size of the BASE object (possibly an array of some
+	   other type such as char used to store the struct).  */
+	memsize = DECL_SIZE_UNIT (base);
+    }
+
+  /* If the flexible array member has a known size use the greater
+     of it and the tail padding in the enclosing struct.
+     Otherwise, when the size of the flexible array member is unknown
+     and the referenced object is not a struct, use the size of its
+     type when known.  This detects sizes of array buffers when cast
+     to struct types with flexible array members.  */
+  if (memsize)
+    {
+      poly_int64 memsz64 = memsize ? tree_to_poly_int64 (memsize) : 0;
+      if (known_lt (baseoff, memsz64))
+	{
+	  memsz64 -= baseoff;
+	  return wide_int_to_tree (TREE_TYPE (memsize), memsz64);
+	}
+      return integer_zero_node;
+    }
 
   /* Return "don't know" for an external non-array object since its
      flexible array member can be initialized to have any number of
      elements.  Otherwise, return zero because the flexible array
      member has no elements.  */
-  return (DECL_EXTERNAL (base) && TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE
+  return (DECL_P (base)
+	  && DECL_EXTERNAL (base)
+	  && (!typematch
+	      || TREE_CODE (basetype) != ARRAY_TYPE)
 	  ? NULL_TREE : integer_zero_node);
 }