gdb: change functions returning value contents to use gdb::array_view

The bug fixed by this [1] patch was caused by an out-of-bounds access to
a value's content.  The code gets the value's content (just a pointer)
and then indexes it with a non-sensical index.

This made me think of changing functions that return value contents to
return array_views instead of a plain pointer.  This has the advantage
that when GDB is built with _GLIBCXX_DEBUG, accesses to the array_view
are checked, making bugs more apparent / easier to find.

This patch changes the return types of these functions, and updates
callers to call .data() on the result, meaning it's not changing
anything in practice.  Additional work will be needed (which can be done
little by little) to make callers propagate the use of array_view and
reap the benefits.

[1] https://sourceware.org/pipermail/gdb-patches/2021-September/182306.html

Change-Id: I5151f888f169e1c36abe2cbc57620110673816f3

1 files changed, 4 insertions, 4 deletions

diff --git a/gdb/c-valprint.c b/gdb/c-valprint.c
index d3071d1..c491d37 100644
--- a/gdb/c-valprint.c
+++ b/gdb/c-valprint.c
@@ -237,7 +237,7 @@ c_value_print_array (struct value *val,
 {
   struct type *type = check_typedef (value_type (val));
   CORE_ADDR address = value_address (val);
-  const gdb_byte *valaddr = value_contents_for_printing (val);
+  const gdb_byte *valaddr = value_contents_for_printing (val).data ();
   struct type *unresolved_elttype = TYPE_TARGET_TYPE (type);
   struct type *elttype = check_typedef (unresolved_elttype);
 
@@ -333,7 +333,7 @@ c_value_print_ptr (struct value *val, struct ui_file *stream, int recurse,
     }
 
   struct type *type = check_typedef (value_type (val));
-  const gdb_byte *valaddr = value_contents_for_printing (val);
+  const gdb_byte *valaddr = value_contents_for_printing (val).data ();
 
   if (options->vtblprint && cp_is_vtbl_ptr_type (type))
     {
@@ -374,7 +374,7 @@ c_value_print_struct (struct value *val, struct ui_file *stream, int recurse,
 	 TYPE_CODE_PTR.)  */
       int offset = TYPE_FIELD_BITPOS (type, VTBL_FNADDR_OFFSET) / 8;
       struct type *field_type = type->field (VTBL_FNADDR_OFFSET).type ();
-      const gdb_byte *valaddr = value_contents_for_printing (val);
+      const gdb_byte *valaddr = value_contents_for_printing (val).data ();
       CORE_ADDR addr = extract_typed_address (valaddr + offset, field_type);
 
       print_function_pointer_address (options, type->arch (), addr, stream);
@@ -405,7 +405,7 @@ c_value_print_int (struct value *val, struct ui_file *stream,
 	 intended to be used as an integer or a character, print
 	 the character equivalent as well.  */
       struct type *type = value_type (val);
-      const gdb_byte *valaddr = value_contents_for_printing (val);
+      const gdb_byte *valaddr = value_contents_for_printing (val).data ();
       if (c_textual_element_type (type, options->format))
 	{
 	  fputs_filtered (" ", stream);