Re: [PATCH v2 2/4] do full type check in BARF_UNLESS_COPYABLE

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 8, 2023, 07:28 UTC
Message-ID: <xmqqy1qdxz67.fsf@gitster.g>
In-Reply-To: <4f161041-b299-f79a-e01b-cc00e2880850@web.de>

René Scharfe <l.s.r@web.de> writes:

Show 5 quoted lines

> Use __builtin_types_compatible_p to perform a full type check if
> possible.  Otherwise fall back to the old size comparison, but add a
> non-evaluated assignment to catch more type mismatches.  It doesn't flag
> copies between arrays with different signedness, but that's as close to
> a full type check as it gets without the builtin, as far as I can see.

This seems to unfortunately break builds for compat/mingw.c

cf. https://github.com/git/git/actions/runs/3865788736/jobs/6589504628#step:4:374

   1848 |                 COPY_ARRAY(&argv2[1], &argv[1], argc);

where the two arrays are "char *const *argv" in the parameter list, and a local variable

#ifndef _MSC_VER
		const
#endif
		char **argv2;

It seems that (const char **) and (char **) are compatible but the pointers themselves being const breaks the type compatibility? Perhaps the latter should be "(optionally const) char *const *argv2"?