[C++] Fix endianness of character argument packs

[Richard Sandiford]

The patch for PR 58708 fixed wide strings being passed as argument packs
but it relied on the host and target having the same endianness.
The patch below uses double_int::from_buffer to handle the case
of differing endiannesses.

Tested on mips64-linux-gnu and mipsisa64-sde-elf (with both endiannesses
in the latter case).  It fixes the pr58708.C failures for big endian.
OK to install?

Thanks,
Richard


gcc/cp/
        PR c++/58708
        * parser.c (make_string_pack): Use double_int::from_buffer.

Index: gcc/cp/parser.c
===================================================================
--- gcc/cp/parser.c     2014-01-29 21:49:13.875748266 +0000
+++ gcc/cp/parser.c     2014-01-29 21:49:20.869759475 +0000
@@ -3808,7 +3808,8 @@ make_string_pack (tree value)
 {
   tree charvec;
   tree argpack = make_node (NONTYPE_ARGUMENT_PACK);
-  const char *str = TREE_STRING_POINTER (value);
+  const unsigned char *str
+    = (const unsigned char *) TREE_STRING_POINTER (value);
   int sz = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (value))));
   int len = TREE_STRING_LENGTH (value) / sz - 1;
   tree argvec = make_tree_vec (2);
@@ -3821,23 +3822,10 @@ make_string_pack (tree value)
 
   /* Fill in CHARVEC with all of the parameters.  */
   charvec = make_tree_vec (len);
-  if (sz == 1)
-    {
-      for (int i = 0; i < len; ++i)
-       TREE_VEC_ELT (charvec, i) = build_int_cst (str_char_type_node, str[i]);
-    }
-  else if (sz == 2)
-    {
-      const uint16_t *num = (const uint16_t *)str;
-      for (int i = 0; i < len; ++i)
-       TREE_VEC_ELT (charvec, i) = build_int_cst (str_char_type_node, num[i]);
-    }
-  else if (sz == 4)
-    {
-      const uint32_t *num = (const uint32_t *)str;
-      for (int i = 0; i < len; ++i)
-       TREE_VEC_ELT (charvec, i) = build_int_cst (str_char_type_node, num[i]);
-    }
+  for (int i = 0; i < len; ++i)
+    TREE_VEC_ELT (charvec, i)
+      = double_int_to_tree (str_char_type_node,
+                           double_int::from_buffer (str + i * sz, sz));
 
   /* Build the argument packs.  */
   SET_ARGUMENT_PACK_ARGS (argpack, charvec);