Re: bzr commit into mysql-5.1-bugteam branch (Alexey.Kopytov:3514) Bug#56709

[Alexey Kopytov]

On 01.10.10 17:57, Davi Arnaut wrote:
> On 10/1/10 10:47 AM, Alexey Kopytov wrote:
>
> [..]
>
>>>
>>> That HAVE_BZERO does not mean that we have the function prototype. In
>>> other others, even thought cmake/autoconf might think bzero is
>>> available, it might not actually be due to the lack of the prototype. As
>>
>> OK, so HAVE_BZERO might be incorrectly defined on some platforms, which
>> is obviously a bug. Its meaning is by definition (which is also assumed
>> by the #ifdef in question): "there is a platform-defined bzero() that we
>> can use".
>
> In autoconf, functions checks are implemented via link checks and I
> assume cmake does the same. It's not exactly incorrectly defined, it
> exists (and links successfully) but the prototype, which is required in
> C++, is only present if the appropriate legacy defines are set.
>

So bzero() is not really available in C++ code on AIX. In this case we 
should not define HAVE_BZERO, that's it. We had a similar issue with 
isinf(), see bug #28240. Doesn't have anything to do with "legacy crap".

>>> for the other questions, they are just hand waving. We do not have waste
>>> time caring for legacy crap.
>>>
>>
>> I did not claim the opposite. To make things dead simple, I say "we
>> should not care about bzero()'s status, just do nothing. If it
>> disappears, it will be mapped to memset() anyway".
>
> The point is that its not so simple. We a better off touching any legacy
> stuff. There is nothing to gain from bzero expect trouble.
>

In my opinion, redefining bzero() on platforms where it is actually 
available is asking for troubles, too.

>> And yes, incorrectly defined HAVE_BZERO is a different issue.
>
> Not exactly incorrect. That's the way autoconf/cmake works.
>

I am well aware how autoconf works. From the autoconf docs:

"For each FUNCTION enumerated in the blank-or-newline-separated argument 
list, define `HAVE_FUNCTION' (in all capitals) if it is available."

I think the only practically usable definition of "available" is "you 
can use it in your code". Since we can't really use bzero() in C++ code 
on AIX, HAVE_BZERO is incorrectly defined. This is what should be fixed 
in bug #55721.

Best regards,
Alexey.