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Subject: Re: [boost] [gsoc] Boost.Process done
From: Boris Schaeling (boris_at_[hidden])
Date: 2010-09-19 16:12:53

Here is another update of the library (again ZIP file updated at
<>; again changes in
Subversion at <>).

What has been changed?

* The library supports now configuring any streams (not only standard
streams but whatever is supported on a platform). This is done through the
new boost::process::context::streams array which replaces the
stdin_behavior, stdout_behavior and stderr_behavior member variables. At
the same time boost::process::child has been changed: This class doesn't
provide the methods get_stdin(), get_stdout() and get_stderr() anymore but
a single method called get_handle(). This new method expects a stream
identifier as parameter and returns a boost::process::handle. It does not
return a boost::process::istream or boost::process::ostream anymore as
Boost.Process doesn't necessarily know if a stream is an input or output
stream. This has the additional advantage though that those who like to
use asynchronous I/O don't get a stream anymore (as they don't need one).
Now you get a handle and decide yourself whether you want to initialize a
stream (for synchronous I/O) or a pipe (for asynchronous I/O).

* Stream behaviors don't expect a boolean anymore to differentiate between
input and output streams. A new enumeration called
boost::process::stream_type has been defined to improve readability.
Furthermore stream behaviors like pipe or named_pipe provide a new
constructor to explicitly specify whether a child's input or output stream
should be configured. This is required on platforms which support
configuring arbitrary many streams (which means POSIX :).

* A bug was fixed in boost::process::detail::basic_status_service which
caused problems when waiting asynchronously for child processes to
terminate on POSIX platforms.

Again I'd appreciate if you could comment on the changes. Especially have
a look at:

* boost::process::stream_type (in boost/process/stream_type.hpp) and
boost::process::stream_id (in boost/process/stream_id.hpp). These types
and files are new.

* the new constructors in boost::process::behavior::pipe,
boost::process::behavior::named_pipe and boost::process::behavior::null
which expect a parameter of type boost::process::stream_type. They allow
developers to explicitly specify whether an input or output stream is
configured as the setting overrides the parameter passed to operator()
(have a look eg. at the test case called "test_posix" in
to see why this is required).

* the class boost::process::context. There is no stdin_behavior,
stdout_behavior and stderr_behavior anymore but a new array called streams.

* the class boost::process::child. As boost::process::context was changed
to support basically arbitrary many streams boost::process::child had to
be updated to provide access to them.

* the implementation of boost::process::create_child() (especially the
POSIX code). As boost::process::context looks differently now
boost::process::create_child() had to be updated.

* the test cases in
to see how boost::process::context and boost::process::child are used now.
The POSIX test cases in this file also use the new streams array to
configure streams with file descriptors greater than 2 (search for
"test_posix"; this is now definitely easier than before as no user-defined
context class is required anymore).

What still has to be done?

* boost::process::context class should provide a boost::function member
variable to bind a callback function instead of requiring developers to
define a subclass and override setup().

* The standard constructor of boost::process::context still tries to
inherit standard streams (which is a problem for Windows GUI applications
which don't have standard streams).

* It might make sense to pass a string to boost::process::create_child()
to specify command line options (instead of storing them one by one in a

* It might be possible to somehow pass options to CreateProcess() on
Windows (which is used by boost::process::create_child()).

* Examples and documentation must be updated.


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