Re: [PATCH v3] git-compat-util.h: implement a different ARRAY_SIZE macro for for safely deriving the size of array

Elia Pinto [off-list ref] writes:

To get number of elements in an array git use the ARRAY_SIZE macro
defined as:

       #define ARRAY_SIZE(x) (sizeof(x)/sizeof((x)[0]))

The problem with it is a possibility of mistakenly passing to it a
pointer instead an array. The ARRAY_SIZE macro as conventionally
defined does not provide good type-safety and the open-coded
approach is more fragile, more verbose and provides no improvement in
type-safety.

Use instead a different but compatible ARRAY_SIZE() macro,
which will also break compile if you try to
use it on a pointer. This implemention revert to the original code
if the compiler doesn't know the typeof and __builtin_types_compatible_p
GCC extensions.

This can ensure our code is robust to changes, without
needing a gratuitous macro or constant. A similar
ARRAY_SIZE implementation also exists in the linux kernel.

Credits to Rusty Russell and his ccan library.

Signed-off-by: Elia Pinto <redacted>
---
 git-compat-util.h | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

This is the third version of the patch.

Compared to the second version:

- Eliminated the autoconf use. I use instead the GCC (and compatible compilers) macros
  for checking if the not portable builtin is supported or not ("Jeff suggestion")
- Changed the name of the macro from _array_size_chk to BARF_IF_IS_NOT_AN_ARRAY i
 ("Junio suggestion. In ALL_CAPS for the Jeff comment )"

Thanks.  Allow me to s/BARF_IF_IS_NOT_AN_ARRAY/BARF_UNLESS_AN_ARRAY/
everywhere for brevity while applying.