boost/preprocessor/seq/for_each_i.hpp fails on gcc 5.4.0 and appleclang 7.3.0

[mjtruog@…]

I have attached test1.cpp which can be compiled with:

g++ -Wall -Wextra -Werror -g -O0 -save-temps -o test1.o -c -fpic test1.cpp

There appears to be more than 1 problem, but this at least shows that BOOST_PP_SEQ_FOR_EACH_I is broken when using these compilers (the string should not be present in the output, but is, with these compilers). Just check the test1.ii file to observe this.

[mjtruog@…]

Example code

[mjtruog@…]

The diff below solves the problem, by bringing the code for the arity 0 case back to the state it was in at version 1.48 (when compared to 1.58):

--- /usr/include/boost/preprocessor/tuple/to_seq.hpp    2016-09-20 13:34:52.926120462 -0700
+++ /usr/include/boost/preprocessor/tuple/to_seq.hpp        2016-09-20 13:35:02.516377864 -0700
@@ -49,7 +49,7 @@
 # endif
 #
 /* An empty array can be passed */
-# define BOOST_PP_TUPLE_TO_SEQ_0() ()
+# define BOOST_PP_TUPLE_TO_SEQ_0()
 #
 # define BOOST_PP_TUPLE_TO_SEQ_1(e0) (e0)
 # define BOOST_PP_TUPLE_TO_SEQ_2(e0, e1) (e0)(e1)

To avoid this bug in BOOST_PP_TUPLE_TO_SEQ I used the work-around below:

#include <boost/preprocessor/list/for_each.hpp>
#include <boost/preprocessor/tuple/to_list.hpp>

#define TUPLE_TO_SEQ_E(r, data, elem) (elem)
#define TUPLE_TO_SEQ(I, T) \
    BOOST_PP_LIST_FOR_EACH(TUPLE_TO_SEQ_E, _, BOOST_PP_TUPLE_TO_LIST(I, T))