[Lldb-commits] [PATCH] D43099: Make LLDB's clang module cache path customizable

Pavel Labath via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Mon Feb 12 02:31:26 PST 2018

labath added a comment.

There are several components in the "command line parsing"

1. argparse: parsing a single string into the individual words (processing quotes, backslashes, etc.)
2. resolving the "command" part of the command line (the "frame variable" part of "frame variable --raw-output FOO")
3. resolving the arguments of a command (the "--raw-output FOO" part)

These parts compose quite nicely, and can be individually replaced. I'll briefly speak about each one :

(1) is very specific to our interactive use case (for command line utilities, the shell/os does the parsing for us). There also isn't anything nearly similar in llvm (afaik).
(2) is also quite specific to how lldb commands are structured, and there also isn't a suitable llvm replacement. This is the level at which the "command aliases" are resolved.
(3) is a fairly generic piece of functionality -- we even implement it by delegating to getopt (in a scarily un-thread-safe way). For this there are *two* competing implementations in llvm: `llvm::cl` and `llvm::opt`. Of these the first one is not suitable for our use case right now as it relies on global variables. Making it work probably would be a bit or work. However, using the second one should be fairly easy, and it should be generic-enough (it's the thing that handles crazy gcc command lines).

The reason I'm spelling it out this way is because I think you were mostly talking about (3), but some of the difficulties Jim pointed out (command aliases) just aren't relevant there.  I don't think llvm::opt handles "shortest match" options yet, but that should be fairly easy to add.  On the flip side, the library has recently gained argument suggestion capabilities (`error: unknown argument '-gllbb', did you mean '-glldb'`), so we would get that for free. Making sure tab completion works there would require a bit of thought, but I think this should not interfere with this library too much (after all, we use getopt now, and it does not support tab completion either).



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