uclinux-2008R1-RC8(bf561)到VDSP5的移植（13）：未命名union的问题

 

  

在include/linux/shed.h中定义了一个结构体：

 

/*

 * NOTE! "signal_struct" does not have it's own

 * locking, because a shared signal_struct always

 * implies a shared sighand_struct, so locking

 * sighand_struct is always a proper superset of

 * the locking of signal_struct.

 */

struct signal_struct {

…

     /* job control IDs */

     pid_t pgrp;

     struct pid *tty_old_pgrp;

 

     union {

         pid_t session __deprecated;

         pid_t __session;

     };

…

};

在include/linux/init_task.h中定义了一个宏来对这个结构体进行初始化：

 

#define INIT_SIGNALS(sig) {                        /

     .count        = ATOMIC_INIT(1),                /

     .wait_chldexit     = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),/

     .shared_pending    = {                         /

         .list = LIST_HEAD_INIT(sig.shared_pending.list),   /

         .signal = {{0}}},                   /

     .posix_timers = LIST_HEAD_INIT(sig.posix_timers),      /

     .cpu_timers   = INIT_CPU_TIMERS(sig.cpu_timers),        /

     .rlim         = INIT_RLIMITS,                      /

     .pgrp         = 0,                        /

     .tty_old_pgrp   = NULL,                        /

     { .__session      = 0},                        /

}

在这里

     { .__session      = 0},                        /

会引发一个错误：

"../../arch/blackfin/kernel/init_task.c", line 38: cc0136: error: union

          "<unnamed>" has no field "__session"

 static struct signal_struct init_signals = INIT_SIGNALS(init_signals);

怎么看都有__session这个成员啊，实际引发这个错误的原因是在结构体中使用了未命名的union。因此必须做如下修改：

struct signal_struct {

…

     /* job control IDs */

     pid_t pgrp;

     struct pid *tty_old_pgrp;

 

     union {

         pid_t session __deprecated;

         pid_t __session;

     }signal_struct_session;

…

};

其实就是随便给这个union定义一个变量。