Re: [Boost-users] Boost::preprocess __VAR_ARGS__ compile fail

Subject: Re: [Boost-users] Boost::preprocess __VAR_ARGS__ compile fail
From: Edward Diener (eldiener_at_[hidden])
Date: 2014-02-11 19:36:04

On 2/11/2014 1:55 AM, garthh wrote:
> This simple piece of code doesn't compile for me in boost 1.54 on MacOSX:
>
> #include <boost/preprocessor.hpp>
> #define debugprintf(...) \
> 	printf(BOOST_PP_SEQ_ELEM(0, BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__)))
> main ()
> {
> 	debugprintf("test");
> }
>
> I've spent ages on it without success. Any suggestions would be greatly
> appreciated!
>
>
> Compile output:
>
> error: too few arguments provided to function-like macro invocation
>          debugprintf("boost test");
>          ^
> main.cpp:15:17: note: expanded from macro 'debugprintf'
> fprintf(stderr, BOOST_PP_SEQ_ELEM(0,
> BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__)));
> \
>                  ^
> /usr/local/Boost/1.54/include/boost/preprocessor/seq/elem.hpp:22:39: note:
> expanded from macro 'BOOST_PP_SEQ_ELEM'
> #    define BOOST_PP_SEQ_ELEM(i, seq) BOOST_PP_SEQ_ELEM_I(i, seq)
>                                        ^
> /usr/local/Boost/1.54/include/boost/preprocessor/seq/elem.hpp:41:45: note:
> expanded from macro 'BOOST_PP_SEQ_ELEM_I'
> #        define BOOST_PP_SEQ_ELEM_I(i, seq)
> BOOST_PP_SEQ_ELEM_II(BOOST_PP_SEQ_ELEM_ ## i seq)
>                                              ^
> /usr/local/Boost/1.54/include/boost/preprocessor/seq/elem.hpp:43:62: note:
> expanded from macro 'BOOST_PP_SEQ_ELEM_II'
> #    define BOOST_PP_SEQ_ELEM_II(im) BOOST_PP_SEQ_ELEM_III(im)
>                                                               ^
> main.cpp:21:2: error: use of undeclared identifier 'BOOST_PP_SEQ_ELEM_III'
>          debugprintf("boost test");

It is quite possible that Boost PP is not setting up your compiler with 
variadic macro support. Would you please try:

#define BOOST_PP_VARIADICS 1

before your code and see if it now works. If it does you might want to 
define BOOST_PP_VARIADICS to 1 on your compiler command line.