On Fri, Sep 11, 2015 at 11:01 AM, Branko Čibej <br...@apache.org> wrote:
> On 10.09.2015 23:50, Evgeny Kotkov wrote: > > Stefan Fuhrmann <stef...@apache.org> writes: > > > > + * Special files like STDIN will have no flags set at all. In that > case, > > + * we can't filter and must allow any operation - which may then fail > at > > + * the APR level further down the stack. > > + */ > > + apr_uint32_t flags = apr_file_flags_get(file); > > + svn_boolean_t supports_read = (flags == 0) || (flags & APR_READ); > > + svn_boolean_t supports_write = (flags == 0) || (flags & APR_WRITE); > > > > Files corresponding to the standard I/O streams actually have the > appropriate > > APR_READ / APR_WRITE flags set starting from APR 1.3 — see, for example, > > apr_file_open_flags_stderr() in [1]. Hence, the (flags == 0) check is > going > > to return false for them. > > > >> Note that this check is not perfect for arbitrary APR file handles > >> (may enable more functions than the handle actually supports) but > >> works correctly for our STD* streams and the files opened through > >> our svn_io_* API. > > The actual problem, to my mind, is that relying on flags to determine if > the > > file allows reading or writing, is fragile. There are examples of > apr_file_t's > > that don't have the corresponding flags, but still allow reading and > writing, > > and svn_stream_from_aprfile2() is going to break for them. > > > > One example would be apr_file_pipe_create() on Unix that sets APR_INHERIT > > flag on the created pipe [2]. Another example is creating a pipe on > Windows > > that currently initializes flags to zero [3]. > > I've reviewed the JavaHL code again and it indeed appears that this is > caused by the difference in implementations of apr_file_pipe_create_ex() > on Windows and elsewhere. The bindings code itself is not > platform-specific; see TunnelContext in > subversion/bindings/javahl/native/OperationContext.cpp. Those pipes get > wrapped into streams deep in the RA layer. > > One could argue that apr_file_pipe_create is broken since it doesn't set > the appropriate flags on the input and output handles, but that doesn't > really help make this particular instance in the bindings code work. > O.k. Then I'll simply revert. -- Stefan^2.
