我在使用C 11 std :: mutex时遇到了一些麻烦
在我的课堂上,我有一个名为std :: mutex的信号量变量.
所以我在我的关键部分之前和之后定位了我的semaphore.lock()和semaphore.unlock()
class Database {
public:
Database(string,string,string);
virtual ~Database();
struct sMyHome getMyHome(void);
struct sPhysical getPhysical(int);
struct sSystemInfo getSystemInfo(void);
void commitSystemInfo(struct sSystemInfo);
struct sTSensors getTSensors(int);
struct sWireless getWireless(int);
struct sWirelessConf getWirelessConf(int);
struct sWirelessStatus getWirelessStatus(int);
private:
void queryMyHome(void);
void queryPhysical(int);
void querySystemInfo(void);
void queryTSensors(int ID);
void queryWireless(int ID);
void queryWirelessConf(int ID);
void queryWirelessStatus(int ID);
string toString(int);
struct sMyHome MyHome;
struct sPhysical Physical[4];
struct sSystemInfo SystemInfo;
struct sTSensors TSensors[32];
struct sWireless Wireless[64];
struct sWirelessConf WirelessConf[64];
struct sWirelessStatus WirelessStatus[64];
MysqL *connection;
mutex semaphore;
};
这是main的一部分,我在其中检索错误：
Database db = Database("192.168.1.10","****","******","******");
但是交叉编译器说
../main.cpp:8:73: error: use of deleted function 'Database::Database(const Database&)'
Database db = Database("192.168.1.10","root","raspberry","DomoHome2");
^
In file included from ../main.cpp:2:0:
../Database.h:79:7: note: 'Database::Database(const Database&)' is implicitly deleted because the default definition would be ill-formed:
class Database {
^
../Database.h:79:7: error: use of deleted function 'std::mutex::mutex(const std::mutex&)'
In file included from ../Database.h:12:0,from ../main.cpp:2:
/Volumes/rpi-crosscompiler-toolchain/arm-none-linux-gnueabi/arm-none-linux-gnueabi/include/c++/4.8.2/mutex:128:5: error: declared here
mutex(const mutex&) = delete;
^
make: *** [main.o] Error 1
这是我的构造函数：
Database::Database(string Address,string Username,string Password,string Database) {
// TODO Auto-generated constructor stub
connection = MysqL_init(NULL);
MysqL_real_connect(connection,Address.c_str(),Username.c_str(),Password.c_str(),Database.c_str(),NULL,0);
}
解决方法
std :: mutex既不可复制也不可移动.在您的班级中加入一个必须使您的班级变得不可复制( – 可移动).如果您希望您的类可以复制或移动,则必须通过自己实现复制/移动构造/赋值来告诉编译器如何复制或移动类的对象.
For example：
class synchronized_int {
mutable std::mutex mtx;
int value;
public:
synchronized_int(int v = 0) : value(v) {}
// Move initialization
synchronized_int(synchronized_int&& other) {
std::lock_guard<std::mutex> lock(other.mtx);
value = std::move(other.value);
other.value = 0;
}
// Copy initialization
synchronized_int(const synchronized_int& other) {
std::lock_guard<std::mutex> lock(other.mtx);
value = other.value;
}
// Move assignment
synchronized_int& operator = (synchronized_int&& other) {
std::lock(mtx,other.mtx);
std::lock_guard<std::mutex> self_lock(mtx,std::adopt_lock);
std::lock_guard<std::mutex> other_lock(other.mtx,std::adopt_lock);
value = std::move(other.value);
other.value = 0;
return *this;
}
// Copy assignment
synchronized_int& operator = (const synchronized_int& other) {
std::lock(mtx,std::adopt_lock);
value = other.value;
return *this;
}
};
