Re: [Xen-devel] [PATCH v2-resend 18/30] libxl: ocaml: use the "string option" type for IDL strings

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-08-27 at 18:44 +0100, Ian Jackson wrote:
> Rob Hoes writes ("[Xen-devel] [PATCH v2-resend 18/30] libxl: ocaml: use the 
> "string option" type for IDL strings"):
> > The libxl IDL is based on C type "char *", and therefore "strings" can
> > by NULL, or be an actual string. In ocaml, it is common to encode such
> > things as option types.
> 
> Can you point me to the existing code this replaces ?  I was looking
> for "Val_string" and "String_val" but couldn't find them.  I think if
> that code is missing it deserves a note in the commit message at least
> (and then surely this new code is currently unused?)

-    "char *":               ("string",                 "%(c)s = 
dup_String_val(%(o)s)", "caml_copy_string(%(c)s)"),
+    "char *":               ("string option",          "%(c)s = 
String_option_val(%(o)s)",  "Val_string_option(%(c)s)"),

So it is replacing uses of dup_String_val (existing function in
tools/ocaml/libs/xl/xenlight_stubs.c) and caml_copy_string (which is an
ocaml provided primitive) with newly defined String_option_val and
Val_string_option which wrap those original function with the Some/None
semantics.

Ian.


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