std::chrono 的问题

Question

我在用 chrono 编译时遇到问题，这里是代码：

时间.hh

#include        <chrono>

class           Time
{
protected:
  std::chrono::steady_clock::time_point _start_t;
  std::chrono::steady_clock::time_point _now;
  std::chrono::steady_clock::time_point _time;
public:
  Time();
  Time(const Time &other);
  Time          &operator=(const Time &other);
  ~Time();
public:
  void          start();
  double        getDurSec();
  double        getDurMilSec();
private:
  void          setNow();
};

编译错误：

g++  -W -Wall -Wextra -I./include -std=c++0x  -c -o src/Time/Time.o src/Time/Time.cpp
In file included from src/Time/Time.cpp:11:0:
./include/Time/Time.hh:21:3: error: ‘steady_clock’ in namespace ‘std::chrono’ does not     name a type
./include/Time/Time.hh:22:3: error: ‘steady_clock’ in namespace ‘std::chrono’ does not name a type
./include/Time/Time.hh:23:3: error: ‘steady_clock’ in namespace ‘std::chrono’ does not name a type
src/Time/Time.cpp: In member function ‘void Time::start()’:
src/Time/Time.cpp:34:2: error: ‘_time’ was not declared in this scope
src/Time/Time.cpp:34:23: error: ‘std::chrono::steady_clock’ has not been declared

等等……

如果您需要更多信息，请告诉我。

Answer 1

您可能使用的是 4.7.0 之前的 g++ 版本，其中未实现 std::chrono::steady_clock。如果是这种情况，您有两种解决方案：

• 将您的 g++ 升级到 4.7.0 或更高版本。
• 改用旧的std::chrono::monotonic_clock。