Re: [RFC PATCH] Move SHA-1 implementation selection into a header file

[Ramsay Jones <ramsay@ramsayjones.plus.com>]

On 14/03/17 23:46, brian m. carlson wrote:
> On Tue, Mar 14, 2017 at 11:42:20PM +0000, Ramsay Jones wrote:
>>
>>
>> On 14/03/17 20:44, Junio C Hamano wrote:
>>> OK, then I'll queue this.  The selection still goes to BASIC_CFLAGS
>>> so the dependencies for re-compilation should be right, I'd think.
>>>
>>> -- >8 --
>>> From: "brian m. carlson" <sandals@crustytoothpaste.net>
>>> Date: Sat, 11 Mar 2017 22:28:18 +0000
>>> Subject: [PATCH] hash.h: move SHA-1 implementation selection into a header file
>>>
>>> Many developers use functionality in their editors that allows for quick
>>> syntax checks, including warning about questionable constructs.  This
>>> functionality allows rapid development with fewer errors.  However, such
>>> functionality generally does not allow the specification of
>>> project-specific defines or command-line options.
>>>
>>> Since the SHA1_HEADER include is not defined in such a case, developers
>>> see spurious errors when using these tools.  Furthermore, while using a
>>> macro as the argument to #include is permitted by C11, it isn't
>>> permitted by C89 and C99, and there are known implementations which
>>> reject it.
>>
>> C99 certainly allows a macro argument to #include (see, 6.10.2-4; there
>> is also an example in 6.10.2-8).
>>
>> I can't remember if it's allowed in C89/C90 (I think it is). I only
>> have immediate access to the C99 and C11 standards (and I can't be
>> bothered to search), so I can't say for sure.
> 
> You're right.  I only have access to N1124 (the C99 final draft), but it
> does allow that.  I could have sworn it was new in C11.  I'm pretty
> certain it isn't allowed in C89, but I don't have access to that
> standard.

My copies of Harbison and Steele (Third and Fifth editions) claim that
Standard C supports it also (by which they mean C89/C90).

> I know there have been reasonably standards-conforming compilers that
> have rejected it in the past, but I can't remember which ones (I think
> they were for proprietary Unices).

Yes, I think that happened to me on Irix, if I recall correctly.

> Junio, do you want to amend the commit message before you merge it?

Yes, please! ;-)

ATB,
Ramsay Jones