[lldb-dev] Odd error involving python subprocess.Popen and gdb-remote hangup on Windows

Zachary Turner zturner at google.com
Thu Aug 28 13:00:33 PDT 2014

Indeed, relying on errno on Windows is not the correct solution for many
reasons.  Actually I don't think converting their error numbers to POSIX
error values is a good solution either.  I'm of the philosophy that if
you're on Windows you should be writing windows code.  Recently I added
eErrorTypeWin32 as a category to lldb::Error.  When you create an error
with that category, you can directly pass it the result of GetLastError().
 Unfortunately, that's literally all I did.  Planned for the future would
be an implementation of Success() and Failure() that returns the right
thing when type == eErrorTypeWin32, and calling FormatMessage() with the
error code so that the message is set automatically.  If you would like to
post patches toward making lldb::Error better handle the case when type ==
eErrorTypeWin32, that would be very welcome.

BTW, where is this particular call to Error::SetErrorToErrno() that this is
coming from?

On Thu, Aug 28, 2014 at 11:53 AM, Ted Woodward <ted.woodward at codeaurora.org>

> I have a python script that automatically launches a simulator and
> connects to it with gdb-remote. Everything works fine on Linux. But when I
> issue the “kill” command on Windows, LLDB crashes.
> This only happens if I launch the simulator (or any external program)
> using python. I’m using subprocess.Popen, but I’ve also tried os.spawnl.
> I’ve traced the problem down to reading errno in Error::SetErrorToErrno().
> In this case, errno is 0, so no error is reported, and the -1 that recv
> returns is used as a buffer size and LLDB crashes. If I don’t launch a
> program using Popen, errno is 2, and everything is handled correctly.
> Stepping into the errno access, GetLastError() is correctly set to
> WSAECONNRESET, but ptd->_terrno, which errno is set to, is 0. This seems
> like a Visual Studio 2012 runtime bug.
> I think maybe we shouldn’t rely on errno on Windows, but call
> GetLastError() and convert their error numbers to POSIX error values.
> Ted
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