C++11 enabled BOOST_SCOPE_EXIT fails to compile with gcc 4.8.5

Bắt đầu bằng cách tái hiện lệnh đã báo cáo với gcc 4.8.5 và ví dụ trong scope_exit.cpp. Sau đó, lần theo quá trình mở rộng macro liên quan trong boost/scope_exit.hpp, tập trung vào lỗi tiền xử lý quanh BOOST_SCOPE_EXIT(&). Hoàn tất khi ví dụ C++11 được cung cấp biên dịch thành công với toolchain đã báo cáo.

#define BOOST_SCOPE_EXIT_CONFIG_USE_LAMBDAS
#include <boost/scope_exit.hpp>

int main() {
    int test = 1;
    BOOST_SCOPE_EXIT(&) {
        test = 2;
    };
}

g++ scope_exit.cpp -std=c++11 -Iboost_1_68_0 produces following error for program above:

In file included from boost_1_68_0/boost/mpl/aux_/integral_wrapper.hpp:22:0,
                 from boost_1_68_0/boost/mpl/int.hpp:20,
                 from boost_1_68_0/boost/mpl/lambda_fwd.hpp:23,
                 from boost_1_68_0/boost/mpl/aux_/na_spec.hpp:18,
                 from boost_1_68_0/boost/mpl/not.hpp:20,
                 from boost_1_68_0/boost/mpl/assert.hpp:17,
                 from boost_1_68_0/boost/scope_exit.hpp:15,
                 from scope_exit.cpp:2:
scope_exit.cpp:6:22: error: pasting "&" and "_BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_VOID_IS" does not give a valid preprocessing token
     BOOST_SCOPE_EXIT(&) {
                      ^
boost_1_68_0/boost/preprocessor/cat.hpp:29:34: note: in definition of macro 'BOOST_PP_CAT_I'
 #    define BOOST_PP_CAT_I(a, b) a ## b
                                  ^
boost_1_68_0/boost/scope_exit.hpp:85:23: note: in expansion of macro 'BOOST_PP_CAT'
     BOOST_PP_IS_UNARY(BOOST_PP_CAT(token, checking_postfix))
                       ^
boost_1_68_0/boost/scope_exit.hpp:92:5: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_BACK_'
     BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_BACK_(token, \
     ^
boost_1_68_0/boost/scope_exit.hpp:111:18: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_VOID_BACK'
     BOOST_PP_IIF(is_void_macro(token), \
                  ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:31:31: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_HANDLE_VOID_'
 # define BOOST_PP_IIF_0(t, f) f
                               ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:32:31: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_HANDLE_SEQ_'
 # define BOOST_PP_IIF_1(t, f) t
                               ^
boost_1_68_0/boost/scope_exit.hpp:177:5: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_'
     BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_( \
     ^
boost_1_68_0/boost/scope_exit.hpp:893:25: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST'
                         BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST(__VA_ARGS__)))
                         ^
boost_1_68_0/boost/scope_exit.hpp:899:9: note: in expansion of macro 'BOOST_SCOPE_EXIT_ID'
         BOOST_SCOPE_EXIT_ID(BOOST_SCOPE_EXIT_AUX_PP_LINE_COUNTER, \
         ^
scope_exit.cpp:6:5: note: in expansion of macro 'BOOST_SCOPE_EXIT'
     BOOST_SCOPE_EXIT(&) {
     ^
scope_exit.cpp:6:22: error: pasting "&" and "BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_THISUNDERSCORE_IS" does not give a valid preprocessing token
     BOOST_SCOPE_EXIT(&) {
                      ^
boost_1_68_0/boost/preprocessor/cat.hpp:29:34: note: in definition of macro 'BOOST_PP_CAT_I'
 #    define BOOST_PP_CAT_I(a, b) a ## b
                                  ^
boost_1_68_0/boost/scope_exit.hpp:85:23: note: in expansion of macro 'BOOST_PP_CAT'
     BOOST_PP_IS_UNARY(BOOST_PP_CAT(token, checking_postfix))
                       ^
boost_1_68_0/boost/scope_exit.hpp:88:5: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_BACK_'
     BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_BACK_(token, \
     ^
boost_1_68_0/boost/scope_exit.hpp:667:18: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_THISUNDERSCORE_BACK'
     BOOST_PP_IIF(BOOST_SCOPE_EXIT_AUX_PP_KEYWORD_IS_THISUNDERSCORE_BACK(\
                  ^
boost_1_68_0/boost/preprocessor/control/expr_iif.hpp:29:36: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_TRAITS_OP'
 # define BOOST_PP_EXPR_IIF_1(expr) expr
                                    ^
boost_1_68_0/boost/preprocessor/list/adt.hpp:35:41: note: in expansion of macro 'BOOST_PP_LIST_FIRST_I'
 #    define BOOST_PP_LIST_FIRST_D(list) BOOST_PP_LIST_FIRST_I list
                                         ^
boost_1_68_0/boost/preprocessor/list/adt.hpp:32:36: note: in expansion of macro 'BOOST_PP_LIST_FIRST_D'
 # define BOOST_PP_LIST_FIRST(list) BOOST_PP_LIST_FIRST_D(list)
                                    ^
boost_1_68_0/boost/preprocessor/list/detail/fold_left.hpp:22:191: note: in expansion of macro 'BOOST_PP_LIST_FIRST'
 # define BOOST_PP_LIST_FOLD_LEFT_1(o, s, l) BOOST_PP_IIF(BOOST_PP_LIST_IS_CONS(l), BOOST_PP_LIST_FOLD_LEFT_2, s BOOST_PP_TUPLE_EAT_3)(o, BOOST_PP_EXPR_IIF(BOOST_PP_LIST_IS_CONS(l), o)(2, s, BOOST_PP_LIST_FIRST(l)), BOOST_PP_LIST_REST(l))
                                                                                                                                                                                               ^
boost_1_68_0/boost/preprocessor/cat.hpp:29:34: note: in expansion of macro 'BOOST_PP_LIST_FOLD_LEFT_1'
 #    define BOOST_PP_CAT_I(a, b) a ## b
                                  ^
boost_1_68_0/boost/scope_exit.hpp:892:17: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_TRAITS'
                 BOOST_SCOPE_EXIT_AUX_TRAITS( \
                 ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:25:39: note: in expansion of macro 'BOOST_PP_IIF_0'
 #    define BOOST_PP_IIF_I(bit, t, f) BOOST_PP_IIF_ ## bit(t, f)
                                       ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:18:37: note: in expansion of macro 'BOOST_PP_IIF_I'
 #    define BOOST_PP_IIF(bit, t, f) BOOST_PP_IIF_I(bit, t, f)
                                     ^
boost_1_68_0/boost/scope_exit.hpp:111:5: note: in expansion of macro 'BOOST_PP_IIF'
     BOOST_PP_IIF(is_void_macro(token), \
     ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:31:31: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_HANDLE_VOID_'
 # define BOOST_PP_IIF_0(t, f) f
                               ^
boost_1_68_0/boost/preprocessor/control/iif.hpp:32:31: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_HANDLE_SEQ_'
 # define BOOST_PP_IIF_1(t, f) t
                               ^
boost_1_68_0/boost/scope_exit.hpp:177:5: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_'
     BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST_( \
     ^
boost_1_68_0/boost/scope_exit.hpp:893:25: note: in expansion of macro 'BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST'
                         BOOST_SCOPE_EXIT_AUX_PP_VOID_LIST(__VA_ARGS__)))
                         ^
boost_1_68_0/boost/scope_exit.hpp:899:9: note: in expansion of macro 'BOOST_SCOPE_EXIT_ID'
         BOOST_SCOPE_EXIT_ID(BOOST_SCOPE_EXIT_AUX_PP_LINE_COUNTER, \
         ^
scope_exit.cpp:6:5: note: in expansion of macro 'BOOST_SCOPE_EXIT'
     BOOST_SCOPE_EXIT(&) {