[Lldb-commits] [PATCH] D40616: ObjectFileELF: Add support for compressed sections

Zachary Turner via lldb-commits lldb-commits at lists.llvm.org
Wed Nov 29 14:51:37 PST 2017

On Wed, Nov 29, 2017 at 1:59 PM Jim Ingham <jingham at apple.com> wrote:

> I'm mostly basing this concern on the bad effect this had on gdb all of
> whose testing was expect based command scraping.  gdb is a tool that's much
> closer to lldb than any of the compiler tools so that experience seems
> relevant.  It's been a decade or so since I worked on gdb, but back when I
> was working on it, you really had to tread very carefully if you wanted to
> change the output of, say, the break command, or to thread listings, etc,
> and a bunch of times I just had to bag some cleanup of output I wanted to
> do because fixing up all the tests was too time consuming.  Because Jason
> and I had both had this experience when we started working on lldb, we
> promised ourselves we wouldn't go down this path again...
Couple of things:

1) I wouldn't dare to use this approach for anything that required
interactivity.  If you need to run one command, extract a value from the
output, and use that value as input to another command, I think that would
be a big mistake.  I have no intention of ever proposing something like

2) FileCheck is very flexible in the way it matches output and tests can be
written so that they are resilient to minor format tweaks.  I have no doubt
that with pure regex matching, or with pretty much any other tool, you
would have a really bad time.  Of course, that doesn't mean it would be
hard to construct an example of a format change that would break a
FileCheck test.  But I think it would happen *far* less frequently than it
did on GDB.  That said, I still understand your concerns that it's fragile,

3) I would not be opposed to a tool called lldb-test, which was basically
just LLDB with a different, and much more limited set of commands, and was
completely non-interactive and would produce output in a format designed
for being scraped, and which never had to be changed since it was never
presented to the user.
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