Re: [PATCH 6/6] do not discard const: the ugly truth

On Thu, Mar 26, 2026 at 04:22:52PM +0100, Michael J Gruber wrote:

Collin and I looked at this one a bit in the earlier thread:

  https://lore.kernel.org/git/e6f7e2eddbc9aef1c21f661420a4b8cb9cd8e2c1.1770095829.git.collin.funk1@gmail.com/

I think it is technically legal to mutate argv strings (which is why this doesn't segfault now), though I think we would prefer to treat them as conceptually const. You do get a segfault with:

  handle_revision_arg("..HEAD", &revs, 0, 0);

which we fortunately never do (we do pass string literals, but never with a range operator).

IMHO the right solution here is to teach the revision-parser not to touch the incoming buffers. We do it only to tie off strings, which can mostly be replaced with xmemdupz(). That's slightly less efficient, but I don't think it would be measurable (it's one allocation that tends to happen a handful of times per program execution, and the rest of the parsing is going to allocate things like commit structs anyway).

I have some patches in that direction, but I haven't gotten around to polishing them yet.

-Peff