/Oi
midl
/{ Oi | Oic | Oif | Oicf}
/Oi
Specifies the
fully-interpreted method for marshalling stub code passed between client and
server.
/Oic
Specifies the
codeless proxy method of marshaling that provides all the features of /Oi and
also further reduces the size of the client stub code for object interfaces.
/Oif
or /Oicf
Specifies the
codeless proxy method of marshaling that includes all the features provided by /Oi
and /Oic but uses a new interpreter ( fast format strings ) that
provides better performance than /Oi or /Oic.
Please note
the restrictions related to supporting platforms, below.
Examples
midl /Oi filename.idl
midl /Oic filename.idl
midl /Oif filename.idl
Remarks
The MIDL 3.0
compiler provides two methods for marshalling code: fully-interpreted (/Oi,
/Oic and /Oif) and mixed-mode (/Os). Mixed-mode is the
default. Some language features are not supported in some modes. In this case,
the compiler automatically switches to the appropriate mode and issues a
warning.
If
performance is a concern, the mixed-mode (/Os) method can be the best approach.
In this mode, the compiler chooses to marshall some parameters inline in the
generated stubs. While this results in larger stub size, it offers increased
performance.
The
fully-interpreted method marshals data completely offline. This considerably
reduces the size of the stub code, but results in decreased performance. Also,
with the fully-interpreted method, there is a limit of 16 parameters for each
procedure. Any procedure containing more than 16 parameters will automatically
be processed in /Os mode. Among the interpreted modes, /Oif
offers the best performance and /Oi offers the best backward
compatibility.
If your
application uses OLE object interfaces and if it will never run on a version of
Microsoft Windows NT earlier than 3.51, you can reduce the size of your client
stub code for object interfaces by using the /Oic option. With this
option the MIDL compiler does not generate any client-side stub code. Since
object interface calls are through vtable pointers, the compiler generates the
proper vtable structures and the application calls the stubs through them.
If your
application will be run only on Microsoft Windows NT 4.0 or later, you
can use the faster /Oif option. Specifically, you may want to use the /Oif
option if your application uses MIDL features that were introduced with MIDL
3.0, such as the wire_marshal
and user_marshal
attributes. If your application uses pipes you must use the /Oif option; if you
specify another mode, the MIDL compiler will switch to /Oif.
To fine-tune
the way your stub code is marshalled, Microsoft RPC provides an ACF optimize
attribute. This attribute is used as an interface attribute or operation
attribute to select the marshalling mode for individual interfaces or for
individual operations.
Calling Conventions
Stubs
generated by the MIDL compiler in the interpreted method using the /Oi,
/Oic, or /Oif switches must be compiled as either a stdcall or a
cdecl procedure during the C compilation. A PASCAL or Fastcall calling
convention will not work. Additionally, the server stub must be compiled as
stdcall.
Supporting Platforms
/Oi is supported on Windows NT 3.5 or later and Windows
95
/Oic is supported on Windows NT 3.51 or later and Windows 95
/Oif is supported on Windows NT 4.0.
See Also