Re: [PATCH] alloc.c: remove alloc_raw_commit_node() function

From: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Date: Jun 19, 2014, 09:55 UTC
Message-ID: <53A2B39A.6040902@ramsay1.demon.co.uk>
In-Reply-To: <20140619091924.GA29478@sigill.intra.peff.net>

On 19/06/14 10:19, Jeff King wrote:

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> On Wed, Jun 18, 2014 at 11:30:50PM +0100, Ramsay Jones wrote:
> 
>> So, the patch below is a slight variation on the original patch.
>> I'm still slightly concerned about portability, but given that it
>> has been at least a decade since I last used a (pre-ANSI) compiler
>> which had a problem with this ...
> 
> For a while some people were compiling git with pretty antique
> compilers, but I do not know if that is the case any more (Junio noted
> recently that we have had trailing commas on arrays and enums in
> builtin/clean.c for the past year, and nobody has complained).
> 
> Maybe those systems have all died off, or maybe those people only
> upgrade every few years, and we are due for an onslaught of portability
> fixes soon. :)

:-P You never know ...

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>> [I have several versions of the C standard that I can use to check
>> up on the legalise, but I'm not sure I can be bothered! ;-) ]
> 
> It was actually pretty easy to find. I only have C99, but "empty macro
> arguments" are listed as one of the changes since C89 in the foreward.

Ah yes, having prompted me to look, it took all of 2 minutes to find it in the C11 .pdf file I have right here ...

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>> diff --git a/alloc.c b/alloc.c
>> index eb22a45..5392d13 100644
>> --- a/alloc.c
>> +++ b/alloc.c
>> @@ -18,9 +18,12 @@
>>  
>>  #define BLOCKING 1024
>>  
>> -#define DEFINE_ALLOCATOR(name, type)				\
>> +#define PUBLIC
>> +#define PRIVATE static
>> +
>> +#define DEFINE_ALLOCATOR(scope, name, type)			\
> 
> I am not sure offhand whether this is more portable or not (it would
> depend on order of macro expansion, and I am not brave enough to read
> through the preprocessor section of the standard carefully).

I suspect it is _slightly_ more portable, but I wouldn't bet any money on it! I may take a look at the standard (it wouldn't be the first time I've looked this up), but it would not help in this situation anyway. The fact that a given compiler does/does-not conform to the standard is useless knowledge if we need to support them.

>                                                               Quick
> reading online suggests that it's OK, but that an extra level of macro
> expansion would not be. And of course the Internet is never wrong. :)

;-)

> I'm inclined to go with it, and deal with it later if we get a
> portability complaint (at which point we are no worse off than we are
> right now).

Hmm, well my initial reaction was to send the more conservative patch first. I wasn't so worried about inlining the code from the macro (I doubt it will change), but I understand (and would often agree with) your concern.

I would be happy with either solution, so I'll let yourself and Junio decide! (sloping shoulders, or what. :) ).

ATB, Ramsay Jones