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

From: Jeff King <[email-masked]>
Date: Thu, 30 Apr 2015 13:44:41 -0400

On Thu, Apr 30, 2015 at 10:41:30AM -0700, Junio C Hamano wrote:

> Elia Pinto <[email-masked]> writes:
> 
> > +#if defined(__GNUC__) && (__GNUC__ >= 3)
> > +# if GIT_GNUC_PREREQ(3, 1)
> > + /* &arr[0] degrades to a pointer: a different type from an array */
> > +# define BARF_IF_IS_NOT_AN_ARRAY(arr)						\
> > +	BUILD_ASSERT_OR_ZERO(!__builtin_types_compatible_p(typeof(arr), \
> > +							typeof(&(arr)[0])))
> > +# else
> > +#  define BARF_IF_IS_NOT_AN_ARRAY(arr) 0 
> > +# endif
> [...]
> 
> Hmmmmmmmm.
> 
>     CC ws.o
> ws.c: In function 'parse_whitespace_rule':
> ws.c:46:3: error: unknown type name 'typeof'
>    for (i = 0; i < ARRAY_SIZE(whitespace_rule_names); i++) {
>    ^
> 
> $ gcc --version
> gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2
> Copyright (C) 2013 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There
> is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
> PURPOSE.

ISTR that you compile with "-std=c89". typeof was added in c99, I think
(and was a GNU extension before that). I wonder if that is fooling the
gcc version-check.

-Peff