奇怪的manpage

man page 中写到：要在dlsym()中使用RTLD_NEXT需要在引入dlfcn.h前定义_GNU_SOURCE：

NOTES

       The symbols RTLD_DEFAULT and RTLD_NEXT are defined by <dlfcn.h> only when _GNU_SOURCE was  defined  before including it.

奇怪的是我怎么测试都不行（FC4），索性把GNU_SOURCE, _GNU_SOURCE, __GNU_SOURCE都定义了，错误依旧：

inter.c:21: error: 'RTLD_NEXT' undeclared (first use in this function)

于是打开/usr/include/dlfcn.h直接看代码，发现这样一段：

#ifdef __USE_GNU

/* If the first argument of `dlsym' or `dlvsym' is set to RTLD_NEXT

   the run-time address of the symbol called NAME in the next shared

   object is returned.  The "next" relation is defined by the order

   the shared objects were loaded.  */

# define RTLD_NEXT      ((void *) -1l)

/* If the first argument to `dlsym' or `dlvsym' is set to RTLD_DEFAULT

   the run-time address of the symbol called NAME in the global scope

   is returned.  */

# define RTLD_DEFAULT   ((void *) 0)

manpage难道会出现这么低级的错误？还是我没有找到问题的真正所在（毕竟很少见__USE_GNU这样的macro）？