tools: ocaml: Handle anonymous struct members of structs in libxl IDL

Julien has a patch "arm: Allow the user to specify the GIC version"
which adds an anonymous struct to libxl_domain_build_info:

    @ -480,6 +486,11 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                           ])),
                      ("invalid", None),
                      ], keyvar_init_val = "LIBXL_DOMAIN_TYPE_INVALID")),
    +
    +
    +    ("arch_arm", Struct(None, [("gic_version", libxl_gic_version),
    +                              ])),
    +
         ], dir=DIR_IN
     )

(libxl_gic_version is an enum). This is not currently supported by the
ocaml genwrap.py. Add a simple pass which handles simple anonymous
unions as top level members of a struct type, but not more deeply
nested since that would be a much more complex change and is not
currently required.

With Juliens patch applied the relevant resulting change to the .mli
is:

    --- tools/ocaml/libs/xl/_libxl_BACKUP_types.mli.in	2015-07-08 11:22:35.000000000 +0100
    +++ tools/ocaml/libs/xl/_libxl_types.mli.in	2015-07-08 12:25:56.000000000 +0100
    @@ -469,6 +477,10 @@ module Domain_build_info : sig

     	type type__union = Hvm of type_hvm | Pv of type_pv | Invalid

    +	type arch_arm__anon = {
    +		gic_version : gic_version;
    +	}
    +
     	type t =
     	{
     		max_vcpus : int;
    @@ -510,6 +522,7 @@ module Domain_build_info : sig
     		ramdisk : string option;
     		device_tree : string option;
     		xl_type : type__union;
    +		arch_arm : arch_arm__anon;
     	}
     	val default : ctx -> ?xl_type:domain_type -> unit -> t
     end

The .ml differs similarly. Without Julien's patch there is no change.

gen_struct is refactored slightly to take the indent level as an
argument, since it is now used at a different level.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Julien Grall <julien.grall@citrix.com>
Cc: Dave Scott <Dave.Scott@citrix.com>
Cc: Rob Hoes <Rob.Hoes@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Rob Hoes <rob.hoes@citrix.com>
Acked-by: David Scott <dave.scott@citrix.com>

tools/ocaml/libs/xl/genwrap.py

@@ -87,7 +87,10 @@ def ocaml_type_of(ty):
     elif isinstance(ty,idl.KeyedUnion):
         return ty.union_name
     elif isinstance(ty,idl.Aggregate):
-        return ty.rawname.capitalize() + ".t"
+        if ty.rawname is None:
+            return ty.anon_struct
+        else:
+            return ty.rawname.capitalize() + ".t"
     else:
         return ty.rawname
 
@@ -111,14 +114,14 @@ def ocaml_instance_of_field(f):
         name = f.name
     return "%s : %s" % (munge_name(name), ocaml_type_of(f.type))
 
-def gen_struct(ty):
+def gen_struct(ty, indent):
     s = ""
     for f in ty.fields:
         if f.type.private:
             continue
         x = ocaml_instance_of_field(f)
-        x = x.replace("\n", "\n\t\t")
-        s += "\t\t" + x + ";\n"
+        x = x.replace("\n", "\n"+indent)
+        s += indent + x + ";\n"
     return s
 
 def gen_ocaml_keyedunions(ty, interface, indent, parent = None):
@@ -140,7 +143,7 @@ def gen_ocaml_keyedunions(ty, interface, indent, parent = None):
             if isinstance(f.type, idl.Struct) and not f.type.has_fields(): continue
             s += "\ntype %s_%s =\n" % (nparent,f.name)
             s += "{\n"
-            s += gen_struct(f.type)
+            s += gen_struct(f.type, indent + "\t")
             s += "}\n"
 
         name = "%s__union" % ty.keyvar.name
@@ -169,6 +172,23 @@ def gen_ocaml_keyedunions(ty, interface, indent, parent = None):
         return None, None
     return s.replace("\n", "\n%s" % indent), union_type
 
+def gen_ocaml_anonstruct(ty, interface, indent, parent = None):
+    s= ""
+
+    if ty.rawname is not None:
+        # Non-anonymous types need no special handling
+        pass
+    elif isinstance(ty, idl.Struct):
+        name = "%s__anon" % parent
+        s += "type %s = {\n" % name
+        s += gen_struct(ty, indent)
+        s += "}\n"
+        ty.anon_struct = name
+    if s == "":
+        return None
+    s = indent + s
+    return s.replace("\n", "\n%s" % indent)
+
 def gen_ocaml_ml(ty, interface, indent=""):
 
     if interface:
@@ -212,9 +232,16 @@ def gen_ocaml_ml(ty, interface, indent=""):
             if union_type is not None:
                 union_types.append(union_type)
 
+        # Handle anonymous structs...
+        for f in ty.fields:
+            anon = gen_ocaml_anonstruct(f.type, interface, "\t", f.name)
+            if anon is not None:
+                s += anon
+                s += "\n"
+
         s += "\ttype t =\n"
         s += "\t{\n"
-        s += gen_struct(ty)
+        s += gen_struct(ty, "\t\t")
         s += "\t}\n"
 
         if ty.init_fn is not None: