I did the kill command, which gets down to ProcessGDBRemote::DoDestroy(), which
sends a “k” packet by calling
GDBRemoteCommunicationClient::SendPacketAndWaitForResponse(), which goes
through a couple layers to
GDBRemoteCommunication::WaitForPacketWithTimeoutMicroSecondsNoLock(). That
calls Communication::Read(), which calls ConnectionFileDescriptor::Read(). That
calls recv(), which returns -1, and then calls Error::SetErrorToErrno().
ConnectionFileDescriptor::Read() then parses the error, assuming the error
value is a POSIX error.
Adding a call to GetLastError() and converting certain error codes to POSIX
errors solved my crash issue. Inside #ifdef _WIN32, of course, because I don’t
want to break my Linux version J.
That reminds me of another (minor) bug. If the call to
SendPacketAndWaitForResponse() doesn’t return PacketResult::Success, LLDB
prints an error:
exit_string.assign("failed to send the k packet");
But the RSP standard says the server doesn’t have to send a response to the “k”
packet. Hanging up is legal. If the return value is
PacketResult::ErrorDisconnected, it shouldn’t print the error.
Ted
From: Zachary Turner [mailto:[email protected]]
Sent: Thursday, August 28, 2014 3:01 PM
To: Ted Woodward
Cc: [email protected]
Subject: Re: [lldb-dev] Odd error involving python subprocess.Popen and
gdb-remote hangup on Windows
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 <[email protected]>
wrote:
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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