Re: [PATCH v4 3/3] regex: use regexec_buf()

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <johannes.schindelin@gmx.de> writes:

> The new regexec_buf() function operates on buffers with an explicitly
> specified length, rather than NUL-terminated strings.
>
> We need to use this function whenever the buffer we want to pass to
> regexec() may have been mmap()ed (and is hence not NUL-terminated).
>
> Note: the original motivation for this patch was to fix a bug where
> `git diff -G <regex>` would crash. This patch converts more callers,
> though, some of which explicitly allocated and constructed
> NUL-terminated strings (or worse: modified read-only buffers to insert
> NULs).
>
> Some of the buffers actually may be NUL-terminated. As regexec_buf()
> uses REG_STARTEND where available, but has to fall back to allocating
> and constructing NUL-terminated strings where REG_STARTEND is not
> available, this makes the code less efficient in the latter case.
>
> However, given the widespread support for REG_STARTEND, combined with
> the improved ease of code maintenance, we strike the balance in favor
> of REG_STARTEND.

The last paragraph can go (2/3 was already justified separately),
and the paragraph before that needs rewording, as you no longer do
the "duplicate, run regexec, and free" dance.

Will comment on the patch text itself later.

Thanks for following it through.  This topic actually fell under my
radar until now.