Re: [PATCH 1/2] tree-diff: fix leak when not HAVE_ALLOCA

On Wed, Sep 15, 2021 at 07:37:05PM -0700, Carlo Marcelo Arenas Belón wrote:

b8ba412bf7 (tree-diff: avoid alloca for large allocations, 2016-06-07)
adds a way to route some bigger allocations out of the stack and free
them through the addition of two conveniently named macros, but leaves
the calls to free the xalloca part, which could be also in the heap,
if the system doesn't HAVE_ALLOCA (ex: macOS).

Add the missing free call, and while at it, change the expression to
match in both macros for easy of readability.

s/easy/ease/ or s/easy of/easier/.

This avoids a leak reported by LSAN as while running t0000 but that
wouldn't fail the test (which will be fixed next) :

Nit; extra space between the closing parenthesis and colon.

OK. So the point is that FAST_ARRAY_ALLOC uses xalloca() for small
arrays. But that might turn into a full-blown malloc() if we don't have
alloca.h. So we need to call xalloca_free() which is a noop if we used
alloca(), but calls free() if we actually used malloc() instead.

Now that I wrote it out myself, I think you basically said as much in
the patch message. But it may have been clearer to say:

    Add the missing free call, [xmalloca_free(), which is a noop if we
    allocated memory in the stack frame, but a real free() if we
    allocaegd in the heap instead].

Thanks,
Taylor