PPAPI: make generator output a pointer to an array correctly.

ppapi/generators/idl_c_proto.py

Index: ppapi/generators/idl_c_proto.py
diff --git a/ppapi/generators/idl_c_proto.py b/ppapi/generators/idl_c_proto.py
index a6179a8f4b677fde965621e9721bb05a767b8435..d029f93d04d795d32aad8b7fe4d71add1eb2266c 100755
--- a/ppapi/generators/idl_c_proto.py
+++ b/ppapi/generators/idl_c_proto.py
@@ -384,6 +384,13 @@ class CGen(object):
 
     # Generate passing type by modifying root type
     rtype = self.GetTypeByMode(node, release, mode)
+    # If this is an array output, change it from type* foo[] to type** foo.
+    # type* foo[] means an array of pointers to type, which is confusing.

[Justin Chuang, 2014/08/19 17:31:13]

nit: optionally elaborate more like this:

Function parameter with 'bar_t* foo[]' is ambiguous. It's legit for different
contexts:
   1. pass an array of pointers to bar_t objects.
   2. the caller prepares 'bar_t* ptr', and pass '&ptr'.
We only need the second context. 

[dmichael (off chromium), 2014/08/19 21:43:21]

I don't mean to come off as harsh, but I'm not sure what point you're trying to
make here. The IDL under discussion reads to me as "an array out-param", not an
"array of pointers":
[out, size_is(array_size)] PP_Size[] preview_sizes
...this currently generates to:
PP_Size* preview_sizes[]
...which is not what is the expressed intent from the IDL. I don't think it
matters whether that line of C has ambiguous intent or not; it's the wrong code
to generate based on the IDL.

If you're arguing that the _IDL_ is ambiguous, that's different. I think it
reads most clearly as "array out-param", so I think the fix is right,
personally.

+    arrayspec = [self.GetArraySpec(array) for array in node.GetListOf('Array')]
+    if mode == 'out' and len(arrayspec) == 1 and arrayspec[0] == '[]':
+      rtype += '*'
+      del arrayspec[0]
+
     if node.IsA('Enum', 'Interface', 'Struct'):
       rname = node.GetName()
     else:
@@ -394,7 +401,6 @@ class CGen(object):
     if '%' in rtype:
       rtype = rtype % rname
     name = node.GetName()
-    arrayspec = [self.GetArraySpec(array) for array in node.GetListOf('Array')]
     callnode = node.GetOneOf('Callspec')
     if callnode:
       callspec = []