[lldb-dap] Enabling LLDB logging to a file does not work in lldb-dap

[ashgti]

If you are using lldb/tools/lldb-dap and you try to enable logging to a file using something like:

lldb> log enable -f /tmp/my_log.txt llvm api

The file is never created and logging is not configured. Instead the logs are sent over the DAP as Console messages which may overwhelm the DAP with a large amount of logging, see

llvm-project/lldb/tools/lldb-dap/lldb-dap.cpp

Line 1520 in 32dd5b2

g_dap.SendOutput(OutputType::Console, llvm::StringRef{buf});

[ashgti]

@walter-erquinigo Do you know if the logging callback is required for Windows support? The original commit 9bcaf6d was around Windows output redirect support but I'm not sure if the logging callback is required for windows or not. If its not required, if we remove the logging callback then the log enable command will write to a file (if configured).

[llvmbot]

@llvm/issue-subscribers-lldb

Author: John Harrison (ashgti)

If you are using lldb/tools/lldb-dap and you try to enable logging to a file using something like:

lldb> log enable -f /tmp/my_log.txt llvm api

The file is never created and logging is not configured. Instead the logs are sent over the DAP as Console messages which may overwhelm the DAP with a large amount of logging, see

llvm-project/lldb/tools/lldb-dap/lldb-dap.cpp

Line 1520 in 32dd5b2

g_dap.SendOutput(OutputType::Console, llvm::StringRef{buf});

[walter-erquinigo]

For context, lldb-dap has to do stdout/stderr redirection because there are some cases in which LLDB outputs error messages directly to the stdout/stderr, which cause the debug session to terminate unless we do the redirection.

The fact that lldb> log enable -f /tmp/my_log.txt llvm api is being redirected seems to be an issue with file descriptors in the Debugger::EnableLog function or somewhere deeper.

Sadly, we can't just disable stdout/stderr redirection :(

[ashgti]

I don't think we need to disable the stdout/stderr redirection, I meant to not use the SBDebugger::Create() with logger callback. When a logger callback is set then it will always call the callback instead of using a file. See #78343 for an example of what I mean.

[ashgti]

This is actually fixed at head due to some recent refectoring in lldb-dap.