Re: extract_unsigned_integer API (Re: [PATCH] Remove MAX_REGISTER_SIZE from frame.c)

[Yao Qi <qiyaoltc at gmail dot com>]

Pedro Alves <palves@redhat.com> writes:

> class extractor
> {
> public:
>    extractor () = default;
>
>    // Get buffer.  Could take a "size" parameter too,
>    // for pre-validation instead of passing "size" to "extract".
>    // Or make that a separate size() method.   Or add a "size" parameter
>    // to the ctor and validate there.  Whatever.  The lambda-based
>    // solution isn't validating upfront either.

My lambda-based solution does validate the boundary before reading
contents to buffer,

+ULONGEST
+extract_unsigned_integer (gdb::function_view<void (gdb_byte *, size_t size)> content_provider,
+                         int len, enum bfd_endian byte_order)
+{
+  if (len > (int) sizeof (ULONGEST))
+    error (_("\
+That operation is not available on integers of more than %d bytes."),
+          (int) sizeof (ULONGEST));
+
+  gdb_byte buf[sizeof (ULONGEST)];
+
+  content_provider (buf, len);
+  return extract_unsigned_integer_1 (buf, len, byte_order);
+}

>
>  extractor extr;
>  frame_unwind_register (frame, regnum, ext.buffer ());

We may overflow ext.buffer (), because the boundary checking is done in
.extract below,

>  return extr.extract (size, byte_order);
>
> Instead of:
>
>   return extract_unsigned_integer ([&] (gdb_byte *buf, size_t size)
> 				   {
> 				     frame_unwind_register (frame, regnum, buf);
> 				   }, size, byte_order);

-- 
Yao (齐尧)