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

>> [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 ...

>> 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. :) ).

Ramsay Jones

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