tools include: Do not use poison with C++

LIST_POISON[12] are used to initialize list_head and hlist_node
pointers, and do void pointer arithmetic, which C++ doesn't like, so, to
avoid drifting from the kernel by introducing some HLIST_POISON to do
away with void pointer math, just make those poisoned pointers be NULL
when building it with a C++ compiler.

Noticed with:

  $ make LLVM_CONFIG=/usr/bin/llvm-config-3.9 LIBCLANGLLVM=1
    CXX      util/c++/clang.o
    CXX	   util/c++/clang-test.o
  In file included from /home/lizj/linux/tools/include/linux/list.h:5:0,
                   from /home/lizj/linux/tools/perf/util/namespaces.h:13,
                   from /home/lizj/linux/tools/perf/util/util.h:15,
                   from /home/lizj/linux/tools/perf/util/util-cxx.h:20,
                   from util/c++/clang-c.h:5,
                   from util/c++/clang-test.cpp:2:
  /home/lizj/linux/tools/include/linux/list.h: In function ‘void list_del(list_head*)’:
  /home/lizj/linux/tools/include/linux/poison.h:14:31: error: pointer of type ‘void *’ used in arithmetic [-Werror=pointer-arith]
   # define POISON_POINTER_DELTA 0
                                 ^
  /home/lizj/linux/tools/include/linux/poison.h:22:41: note: in expansion of macro ‘POISON_POINTER_DELTA’
   #define LIST_POISON1  ((void *) 0x100 + POISON_POINTER_DELTA)
                                           ^
  /home/lizj/linux/tools/include/linux/list.h:107:16: note: in expansion of macro ‘LIST_POISON1’
    entry->next = LIST_POISON1;
                  ^
  In file included from /home/lizj/linux/tools/perf/util/namespaces.h:13:0,
                   from /home/lizj/linux/tools/perf/util/util.h:15,
                   from /home/lizj/linux/tools/perf/util/util-cxx.h:20,
                   from util/c++/clang-c.h:5,
                   from util/c++/clang-test.cpp:2:
  /home/lizj/linux/tools/include/linux/list.h:107:14: error: invalid conversion from ‘void*’ to ‘list_head*’ [-fpermissive]

Reported-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Philip Li <philip.li@intel.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-m5ei2o0mjshucbr28baf5lqz@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/tools/include/linux/poison.h b/tools/include/linux/poison.h
index 51334ed..f306a76 100644
--- a/tools/include/linux/poison.h
+++ b/tools/include/linux/poison.h
@@ -14,6 +14,10 @@
 # define POISON_POINTER_DELTA 0
 #endif
 
+#ifdef __cplusplus
+#define LIST_POISON1  NULL
+#define LIST_POISON2  NULL
+#else
 /*
  * These are non-NULL pointers that will result in page faults
  * under normal circumstances, used to verify that nobody uses
@@ -21,6 +25,7 @@
  */
 #define LIST_POISON1  ((void *) 0x100 + POISON_POINTER_DELTA)
 #define LIST_POISON2  ((void *) 0x200 + POISON_POINTER_DELTA)
+#endif
 
 /********** include/linux/timer.h **********/
 /*