c - 我不明白为什么编译器给我这个代码的错误

Question

我有以下 C 代码，我认为它非常正确。然而，clang 编译器(实际上是 gcc 或任何其他 C 编译器)不这么认为。

typedef struct
{
    struct timeval td_start;
    struct timeval td_end;
} Timer;

void startTimer( struct Timer* ptimer ) 
{
    gettimeofday( &(ptimer->td_start), NULL );
}

void stopTimer( struct Timer* ptimer ) 
{
    gettimeofday( &(ptimer->td_end), NULL );
}

编译器给出以下警告和错误消息。知道这里出了什么问题吗？

./timing.h:14:25: warning: declaration of 'struct Timer' will not be visible
      outside of this function [-Wvisibility]
void startTimer( struct Timer* ptimer )
                        ^
./timing.h:16:27: error: incomplete definition of type 'struct Timer'
    gettimeofday( &(ptimer->td_start), NULL );
                    ~~~~~~^
./timing.h:14:25: note: forward declaration of 'struct Timer'
void startTimer( struct Timer* ptimer )
                        ^
./timing.h:19:24: warning: declaration of 'struct Timer' will not be visible
      outside of this function [-Wvisibility]
void stopTimer( struct Timer* ptimer )
                       ^
./timing.h:21:27: error: incomplete definition of type 'struct Timer'
    gettimeofday( &(ptimer->td_end), NULL );
                    ~~~~~~^
./timing.h:19:24: note: forward declaration of 'struct Timer'
void stopTimer( struct Timer* ptimer )

Answer 1

删除 struct 关键字(不需要它，因为您已经typedef编辑了结构):

void startTimer( Timer* ptimer ) 
{
  ...

void stopTimer( Timer* ptimer ) 
{
  ...

或者，删除 typedef:

struct Timer
{
    struct timeval td_start;
    struct timeval td_end;
};

void startTimer( struct Timer* ptimer ) 
{
  ...

void stopTimer( struct Timer* ptimer ) 
{
  ...

有关详细信息，请参阅 Why should we typedef a struct so often in C?