Re: [PATCH] Add use of asprintf() - Mailing list pgsql-hackers

On Tue, Oct 15, 2013 at 2:18 AM, Peter Eisentraut <peter_e@gmx.net> wrote:
> On Mon, 2013-10-14 at 23:08 +1300, David Rowley wrote:
>
>>
>> Looks like something like:
>>
>>
>> #ifndef WIN32
>> #define HAVE_VA_COPY 1
>> #endif
>>
>>
>> would need to be added to asprintf.c, but also some work needs to be
>> done with mcxt.c as it uses va_copy unconditionally. Perhaps just
>> defining a macro for va_copy would be better for windows. I was not
>> quite sure the best header file for such a macro so I did not write a
>> patch to fix it.
>
> Does Windows not have va_copy?  What do they use instead?

No, Windows doesn't have va_copy, instead they use something like below:
#define va_copy(dest, src) (dest = src)

Please refer below link for details of porting va_copy() on Windows:
http://stackoverflow.com/questions/558223/va-copy-porting-to-visual-c

I could see that there is similar handling in code of vasprintf(),
such that if va_copy is not available then directly assign src to dst.

#if defined(HAVE_VA_COPY)
va_copy(ap2, ap);
#define my_va_end(ap2) va_end(ap2)
#elif defined(HAVE___BUILTIN_VA_COPY)
__builtin_va_copy(ap2, ap);
#define my_va_end(ap2) __builtin_va_end(ap2)
#else
ap2 = ap;
#define my_va_end(ap2) do {} while (0)
#endif

I think rather than having writing code like above at places where
va_copy is used, we can use something like:
#ifdef WIN32
#define va_copy(dest, src) (dest = src)
#endif

and define HAVE_VA_COPY to 1 for non-windows platform.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com