Phoenix unconditionally sets BOOST_PROTO_MAX_ARITY

[m.champlon@…]

Hi,

The following :

#define BOOST_PROTO_MAX_ARITY 20
#include <boost/phoenix.hpp>

exhibits the following warning with msvc 2010 and boost 1.50 :

1>C:\dev\include\boost/phoenix/core/limits.hpp(19): warning C4005: 'BOOST_PROTO_MAX_ARITY' : macro redefinition

This is rather inconvenient for the user of several libraries. I suggest to modify limits.hpp to change :

#if defined(BOOST_PHOENIX_LIMIT)
#define BOOST_PROTO_MAX_ARITY BOOST_PHOENIX_LIMIT

to :

 #if defined(BOOST_PHOENIX_LIMIT)
# if !defined( BOOST_PROTO_MAX_ARITY )
#  define BOOST_PROTO_MAX_ARITY BOOST_PHOENIX_LIMIT
# elif (BOOST_PROTO_MAX_ARITY < BOOST_PHOENIX_LIMIT)
#  error "BOOST_PROTO_MAX_ARITY is set too low"
# endif

or see the attached patch.

Thanks, MAT.

[Mathieu Champlon <m.champlon@…>]

I added a test case to verify that the following code fails to compile

#define BOOST_PROTO_MAX_ARITY 10
#define BOOST_PHOENIX_LIMIT 20
#include <boost/phoenix.hpp>

because in case BOOST_PROTO_MAX_ARITY has been previously defined (for instance by including another boost library) there isn't much that can be done but #error'ing to the user.

boost_phoenix_7166.patch includes both the test case and the fix already included in the previous patch.

Cheers,

MAT.

[Mathieu Champlon <m.champlon@…>]

I forgot to mention that this solution was also suggested in this thread : ​http://boost.2283326.n4.nabble.com/phoenix-not-playing-nice-with-other-libs-td3489758.html

[John Fletcher <J.P.Fletcher@…>]

This patch and test are now released on develop for testing.