[Bug 2474] Program wants to call file in same directory as program, but claims it cannot find it.

[Wine Bugs]

http://bugs.winehq.org/show_bug.cgi?id=2474

------- Additional Comments From [e-mail]  2005-22-03 11:54 -------
I have been reviewing what happens when MP3GainGUI starts up that triggers the
first of the errors (the dialog box that claims mp3gain.exe could not be found).
The source code of MP3GainGUI has been helpful for this.

MP3GainGui tries to invoke mp3gain.exe at startup in order to get the program
version. This backend reports its version on stdout when invoked with a /v 
switch. So, the VB frontend opens a pipe and connects the backend stdout to it
in order to read the version string from it. Since the routine to fetch a
program's stdout is a generic one, and the execution of the program might take
a while, the routine polls for available data from the pipe (much in the way the
select() call is used in Unix) before reading, and calls DoEvents (a VB keyword
that yields control to the GUI in order to process window events) if no data
is available. The function called to poll for available data is PeekNamedPipe(),
with a (supposedly) NULL buffer pointer, and a buffer length of zero. The Wine 
implementation of PeekNamedPipe() checks for a NULL pointer before attempting
to read data from the pipe with recv() and the MSG_PEEK flag.

The problem arises because the VB frontend fails at specifying a NULL pointer
for the buffer pointer of PeekNamedPipe(). Because of some poorly-documented
rule about the way an Any parameter in VB behaves, the attempt to pass a
literal 0& (which is, as far as I can remeber, an equivalent of "0L" in C) to
the lpBuffer parameter (declared as Any in the VB file) does NOT translate into
a NULL pointer, but to a non-NULL pointer that points to the zero value (or so
I think). Then PeekNamedPipe() receives a non-NULL pointer, which it interprets
as a valid buffer, and fails to check that the buffer length is set to 0, so it
end up trying to perform a zero-length peek on an invalid buffer with recv().
This operation is (apparently) not supported, and so it says in the errno value.

The PeekNamedPipe() function should check for the buffer length as well as the
buffer pointer before trying to perform the recv() peek on the pipe.