add general #ifdef

[thirdwing]

This PR adds general #ifdef, not for OSX only.

It follows the manner in https://github.com/python/cpython/blob/master/Modules/posixmodule.c#L9551

[eddelbuettel]

OMG that is so obviously better.

What do you then get on OS X for library(RcppGetconf); dim(getAll)[1] ? Ie how do we drop from the 320 we on Linux?

Thanks so much.

[thirdwing]

On my machine:

> dim(getAll())[1]
[1] 194
> getAll()
                                  key                         value type
1                            LINK_MAX                         32767 path
2                     _POSIX_LINK_MAX                         32767 path
3                           MAX_CANON                               path
4                    _POSIX_MAX_CANON                               path
5                           MAX_INPUT                               path
6                    _POSIX_MAX_INPUT                               path
7                            NAME_MAX                           255 path
8                     _POSIX_NAME_MAX                           255 path
9                            PATH_MAX                          1024 path
10                    _POSIX_PATH_MAX                          1024 path
11                           PIPE_BUF                           512 path
12                    _POSIX_PIPE_BUF                           512 path
13                    _POSIX_ASYNC_IO                             1 path
14            _POSIX_CHOWN_RESTRICTED                        200112 path
15                    _POSIX_NO_TRUNC                        200112 path
16                     _POSIX_PRIO_IO                             0 path
17                     _POSIX_SYNC_IO                             0 path
18                    _POSIX_VDISABLE                               path
19                            ARG_MAX                        262144  sys
20                         ATEXIT_MAX                    2147483647  sys
21                          CHILD_MAX                           709  sys
22                            CLK_TCK                           100  sys
23                        LOGNAME_MAX                           255  sys
24                        NGROUPS_MAX                            16  sys
25                   NSS_BUFLEN_GROUP                          4096  sys
26                  NSS_BUFLEN_PASSWD                          4096  sys
27                           OPEN_MAX                           256  sys
28                           PAGESIZE                          4096  sys
29                          PAGE_SIZE                          4096  sys
30                           PASS_MAX                           128  sys
31      PTHREAD_DESTRUCTOR_ITERATIONS                             4  sys
32                   PTHREAD_KEYS_MAX                           512  sys
33                  PTHREAD_STACK_MIN                          8192  sys
34                PTHREAD_THREADS_MAX                                sys
35                       TTY_NAME_MAX                           255  sys
36                         TZNAME_MAX                           255  sys
37                  _NPROCESSORS_CONF                             4  sys
38                  _NPROCESSORS_ONLN                             4  sys
39                     _POSIX_ARG_MAX                        262144  sys
40             _POSIX_ASYNCHRONOUS_IO                                sys
41                   _POSIX_CHILD_MAX                           709  sys
42                       _POSIX_FSYNC                        200112  sys
43                 _POSIX_JOB_CONTROL                        200112  sys
44                _POSIX_MAPPED_FILES                        200112  sys
45                     _POSIX_MEMLOCK                                sys
46               _POSIX_MEMLOCK_RANGE                                sys
47           _POSIX_MEMORY_PROTECTION                        200112  sys
48             _POSIX_MESSAGE_PASSING                                sys
49                 _POSIX_NGROUPS_MAX                            16  sys
50                    _POSIX_OPEN_MAX                           256  sys
51              _POSIX_PRIORITIZED_IO                                sys
52         _POSIX_PRIORITY_SCHEDULING                                sys
53            _POSIX_REALTIME_SIGNALS                                sys
54                   _POSIX_SAVED_IDS                             1  sys
55                  _POSIX_SEMAPHORES                                sys
56       _POSIX_SHARED_MEMORY_OBJECTS                                sys
57                  _POSIX_STREAM_MAX                           256  sys
58             _POSIX_SYNCHRONIZED_IO                                sys
59                     _POSIX_THREADS                        200112  sys
60       _POSIX_THREAD_ATTR_STACKADDR                        200112  sys
61       _POSIX_THREAD_ATTR_STACKSIZE                        200112  sys
62  _POSIX_THREAD_PRIORITY_SCHEDULING                                sys
63         _POSIX_THREAD_PRIO_INHERIT                                sys
64         _POSIX_THREAD_PRIO_PROTECT                                sys
65       _POSIX_THREAD_PROCESS_SHARED                        200112  sys
66       _POSIX_THREAD_SAFE_FUNCTIONS                        200112  sys
67                      _POSIX_TIMERS                                sys
68                          TIMER_MAX                                sys
69                  _POSIX_TZNAME_MAX                           255  sys
70                     _POSIX_VERSION                        200112  sys
71                       _XOPEN_CRYPT                             1  sys
72                    _XOPEN_ENH_I18N                             1  sys
73                      _XOPEN_LEGACY                                sys
74                    _XOPEN_REALTIME                                sys
75            _XOPEN_REALTIME_THREADS                                sys
76                         _XOPEN_SHM                             1  sys
77                        _XOPEN_UNIX                             1  sys
78                     _XOPEN_VERSION                           600  sys
79                 _XOPEN_XCU_VERSION                             4  sys
80                        BC_BASE_MAX                            99  sys
81                         BC_DIM_MAX                          2048  sys
82                       BC_SCALE_MAX                            99  sys
83                      BC_STRING_MAX                          1000  sys
84                   COLL_WEIGHTS_MAX                             2  sys
85                      EXPR_NEST_MAX                            32  sys
86                           LINE_MAX                          2048  sys
87                 POSIX2_BC_BASE_MAX                            99  sys
88                  POSIX2_BC_DIM_MAX                          2048  sys
89                POSIX2_BC_SCALE_MAX                            99  sys
90               POSIX2_BC_STRING_MAX                          1000  sys
91                   POSIX2_CHAR_TERM                        200112  sys
92            POSIX2_COLL_WEIGHTS_MAX                             2  sys
93                      POSIX2_C_BIND                        200112  sys
94                       POSIX2_C_DEV                        200112  sys
95               POSIX2_EXPR_NEST_MAX                            32  sys
96                    POSIX2_FORT_DEV                                sys
97                    POSIX2_FORT_RUN                        200112  sys
98                   _POSIX2_LINE_MAX                          2048  sys
99                    POSIX2_LINE_MAX                          2048  sys
100                  POSIX2_LOCALEDEF                        200112  sys
101                 POSIX2_RE_DUP_MAX                           255  sys
102                     POSIX2_SW_DEV                        200112  sys
103                        POSIX2_UPE                        200112  sys
104                    POSIX2_VERSION                        200112  sys
105                        RE_DUP_MAX                           255  sys
106                              PATH /usr/bin:/bin:/usr/sbin:/sbin conf
107                           CS_PATH /usr/bin:/bin:/usr/sbin:/sbin conf
108                 _XBS5_ILP32_OFF32                                sys
109           XBS5_ILP32_OFF32_CFLAGS                               conf
110          XBS5_ILP32_OFF32_LDFLAGS                               conf
111             XBS5_ILP32_OFF32_LIBS                               conf
112        XBS5_ILP32_OFF32_LINTFLAGS                               conf
113                _XBS5_ILP32_OFFBIG                             1  sys
114          XBS5_ILP32_OFFBIG_CFLAGS                         -W 32 conf
115         XBS5_ILP32_OFFBIG_LDFLAGS                         -W 32 conf
116            XBS5_ILP32_OFFBIG_LIBS                               conf
117       XBS5_ILP32_OFFBIG_LINTFLAGS                               conf
118                  _XBS5_LP64_OFF64                             1  sys
119            XBS5_LP64_OFF64_CFLAGS                         -W 64 conf
120           XBS5_LP64_OFF64_LDFLAGS                         -W 64 conf
121              XBS5_LP64_OFF64_LIBS                               conf
122         XBS5_LP64_OFF64_LINTFLAGS                               conf
123                _XBS5_LPBIG_OFFBIG                             1  sys
124          XBS5_LPBIG_OFFBIG_CFLAGS                         -W 64 conf
125         XBS5_LPBIG_OFFBIG_LDFLAGS                         -W 64 conf
126            XBS5_LPBIG_OFFBIG_LIBS                               conf
127       XBS5_LPBIG_OFFBIG_LINTFLAGS                               conf
128             _POSIX_V6_ILP32_OFF32                                sys
129       POSIX_V6_ILP32_OFF32_CFLAGS                               conf
130      POSIX_V6_ILP32_OFF32_LDFLAGS                               conf
131         POSIX_V6_ILP32_OFF32_LIBS                               conf
132            _POSIX_V6_ILP32_OFFBIG                             1  sys
133      POSIX_V6_ILP32_OFFBIG_CFLAGS                         -W 32 conf
134     POSIX_V6_ILP32_OFFBIG_LDFLAGS                         -W 32 conf
135        POSIX_V6_ILP32_OFFBIG_LIBS                               conf
136              _POSIX_V6_LP64_OFF64                             1  sys
137        POSIX_V6_LP64_OFF64_CFLAGS                         -W 64 conf
138       POSIX_V6_LP64_OFF64_LDFLAGS                         -W 64 conf
139          POSIX_V6_LP64_OFF64_LIBS                               conf
140            _POSIX_V6_LPBIG_OFFBIG                             1  sys
141      POSIX_V6_LPBIG_OFFBIG_CFLAGS                         -W 64 conf
142     POSIX_V6_LPBIG_OFFBIG_LDFLAGS                         -W 64 conf
143        POSIX_V6_LPBIG_OFFBIG_LIBS                               conf
144              _POSIX_ADVISORY_INFO                                sys
145                   _POSIX_BARRIERS                                sys
146            _POSIX_CLOCK_SELECTION                                sys
147                    _POSIX_CPUTIME                                sys
148             _POSIX_THREAD_CPUTIME                                sys
149               _POSIX_FILE_LOCKING                          4096  sys
150            _POSIX_MONOTONIC_CLOCK                                sys
151        _POSIX_READER_WRITER_LOCKS                        200112  sys
152                 _POSIX_SPIN_LOCKS                                sys
153                     _POSIX_REGEXP                        200112  sys
154                      _POSIX_SHELL                        200112  sys
155                      _POSIX_SPAWN                                sys
156            _POSIX_SPORADIC_SERVER                                sys
157     _POSIX_THREAD_SPORADIC_SERVER                                sys
158                   _POSIX_TIMEOUTS                                sys
159       _POSIX_TYPED_MEMORY_OBJECTS                                sys
160                        POSIX2_PBS                                sys
161             POSIX2_PBS_ACCOUNTING                                sys
162                 POSIX2_PBS_LOCATE                                sys
163                  POSIX2_PBS_TRACK                                sys
164                POSIX2_PBS_MESSAGE                                sys
165                       SYMLOOP_MAX                            32  sys
166                        STREAM_MAX                           256  sys
167                    AIO_LISTIO_MAX                            90  sys
168                           AIO_MAX                            90  sys
169                AIO_PRIO_DELTA_MAX                                sys
170                    DELAYTIMER_MAX                                sys
171                     HOST_NAME_MAX                           255  sys
172                    LOGIN_NAME_MAX                           255  sys
173                       MQ_OPEN_MAX                                sys
174                       MQ_PRIO_MAX                                sys
175                      _POSIX_TRACE                                sys
176         _POSIX_TRACE_EVENT_FILTER                                sys
177              _POSIX_TRACE_INHERIT                                sys
178                  _POSIX_TRACE_LOG                                sys
179                         RTSIG_MAX                                sys
180                     SEM_NSEMS_MAX                         87381  sys
181                     SEM_VALUE_MAX                         32767  sys
182                      SIGQUEUE_MAX                                sys
183                      FILESIZEBITS                            64 path
184              POSIX_ALLOC_SIZE_MIN                             1 path
185          POSIX_REC_INCR_XFER_SIZE                          4096 path
186           POSIX_REC_MAX_XFER_SIZE                         65536 path
187           POSIX_REC_MIN_XFER_SIZE                          4096 path
188              POSIX_REC_XFER_ALIGN                          4096 path
189                       SYMLINK_MAX                           255 path
190                   POSIX2_SYMLINKS                             1 path
191                              IPV6                        200112  sys
192                       RAW_SOCKETS                                sys
193                       _POSIX_IPV6                        200112  sys
194                _POSIX_RAW_SOCKETS                                sys
>