Eric Lemings wrote:
-----Original Message-----
From: Travis Vitek [mailto:[EMAIL PROTECTED]
Sent: Monday, June 23, 2008 4:59 PM
To: dev@stdcxx.apache.org
Subject: RE: svn commit: r668225 -
/stdcxx/branches/4.3.x/etc/config/src/VA_LIST_FUNC_MACRO.cpp
Eric Lemings wrote:
Martin Sebor wrote:
My point was that I couldn't find a way to use a feature
that depends on variadic macros on platforms where they
are not supported. In other words, I can't picture what
the #else branch below would look like:
#ifndef _RWSTD_NO_VARIADIC_MACROS
# define RW_ASSERT(expr, ...) \
rw_assert (expr, 0, __LINE__, __VA_LIST__)
#else
# define RW_ASSERT(expr, ???) ...
#endif
You're right. There is no backward-compatible workaround which
essentially rules out using variadic macros in these cases.
Which is why I don't think we'll be able to (or need to) use the
config macro in our code.
I think I've showed this trick before, but it won't work with template
parameters, only function parameters.
Right. This "trick" obviates the need for variadic macros in the
case of the rw_xxx() functions.
(Note that the trick isn't a general replacement for variadic macros
because it relies on a runtime mechanism while variadic macros are
a compile-time one.)
struct Variadic
{
void operator()(const char* fmt, ...);
};
#define VARIADIC Variadic().operator()
Of course you would use it like this...
VARIADIC("hello %s", "world!");
Had forgotten about that. :)
So, we have something like this:
There's no need for the additional complexity when we can just use
the #else case unconditionally. The !_RWSTD_NO_VARIADIC_MACROS case
provides no advantage over the workaround.
#ifndef _RWSTD_NO_VARIADIC_MACROS
# define RW_ASSERT(expr, ...) \
rw_assert (expr, 0, __LINE__, __VA_LIST__)
#else
struct __rw_assert {
int operator()(int expr, const char* file, int line,
const char* fmt, ...) {
va_list va;
va_start (va, fmt);
_rw_vdiag (diag_assert, 0 == expr, file, line, fmt, va);
va_end (va);
return success;
}
};
# define RW_ASSERT __rw_assert().operator()
#endif
That pretty close?
And why is there a 2nd parameter in rw_assert() if its never used? :P
Brad.
