(LLDB on MacOs Catalina) Shell Expansion Failed

Question

When trying to use the r or run commands in lldb I get an error like this: error: shell expansion failed (reason: invalid JSON). consider launching with 'process launch'.

It works when I just use process launch but I really do not feel like doing that.

Is there any way I could make either an alias or make shell expansions not fail?

Answer 1

The way lldb does shell expansion is to run a little tool called lldb-argdumper (it is in Xcode.app/Contents/SharedFrameworks/LLDB.framework/Resources on macOS) with the command arguments that you passed. lldb-argdumper wraps the contents of argv as JSON, and writes that to stdout. lldb then parses the JSON back into args and inserts the args one by oneinto the argc/argv array when it launches the process.

Something in the output is not getting properly wrapped. You can probably see what it is by looking at the output of lldb-argdumper with your arguments. Whatever it is, it's a bug, so if you can reproduce it please file with your example with http://bugs.llvm.org.

(lldb) command alias run-no-shell process launch -X 0 --

will produce an alias that doesn't do shell expansion. You can also put this in your ~/.lldbinit.

Answer 2

I ran into this recently. TL;DR: make sure your shell does not echo anything during initialization. Run <your-shell> -c date to confirm; only the date should be printed.

The problem was that my shell's initialization file was echoing some stuff, which was getting prepended to lldb-argdumper's JSON output. (lldb doesn't run lldb-argdumper directly; it invokes your default shell to run lldb-argdumper.)

Specifically, I use fish as my shell, which does not have separate initialization paths for interactive and non-interactive sessions. (See this issue for discussion of whether this is good.) bash and zsh have separate init files for interactive/non-interactive sessions, which makes avoiding this problem slightly easier.