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C++11 variadic function and format attribute


Hi all,

I was working on some C++11 template hacks to be able to pass C++ objects to a
function wrapping printf. What I want to do looks like this, where convert
might do fancy things like create string representations of objects:

template<typename... Args>
void Printf(const char* format, Args&&... args)
{
     printf(format, convert(std::forward<Args>(args))...);
}

However, it seems that this is incompatible with the
__attribute__((format(printf, 1, 2))) applied to printf.

When trying to call this function as
 Printf("%d\n", 3);
I get the following errors:
 In function 'void Printf(const char*, Args&& ...) [with Args = int]':
   instantiated from here
 warning: format not a string literal, argument types not checked

Unfortunately, the compiler believes my format string is not a string literal,
but it is! It's really important to me that the arguments are checked against
the format string at compile time, as this catches serious bugs sooner.

I tried this on gcc-4.4 through 4.7 (and clang 3.0), with the same result.
Is this a compiler bug? Is there a work-around for this problem?

Thanks,
Diego


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