就是int b = 1; int & a = b; a - 1;会报出警告
时间: 2023-08-07 11:03:03 浏览: 75
是的,这段代码会产生警告,因为在对 a 做减法运算时,编译器会将其转换为对 b 做减法运算。由于 a 是一个引用,它实际上指向的是变量 b 的地址,因此对 a 做减法运算实际上是对 b 做减法运算,而不是对 a 做减法运算。因此,这段代码的结果将是将 b 的值减去 1,而不是将 a 的值减去 1。为避免这种情况,请使用指针而不是引用来声明变量 a,这样就可以避免编译器进行隐式类型转换了。
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#include <windows.h> #include <QString> #include <QMessageBox> int main(int argc, char *argv[]) { HANDLE mutex = ::CreateMutex(Q_NULLPTR, true, (LPCWSTR)qApp->applicationName().toStdWString().c_str()); if (GetLastError() == ERROR_ALREADY_EXISTS) { QMessageBox waringBox(QMessageBox::Warning, QStringLiteral("警告"), QStringLiteral("当前程序已运行,不能再次运行!")); waringBox.setButtonText(QMessageBox::Ok, QStringLiteral("确定")); waringBox.setStandardButtons(QMessageBox::Ok); waringBox.exec(); ::CloseHandle(mutex); return 0; } // 获取当前登录用户的会话ID DWORD sessionId; ProcessIdToSessionId(GetCurrentProcessId(), &sessionId); // 遍历所有用户会话,关闭其他用户会话中的该程序进程 DWORD sessionCount; if (ProcessIdToSessionId(GetCurrentProcessId(), &sessionId) && WTSQuerySessionInformationW(WTS_CURRENT_SERVER_HANDLE, WTS_CURRENT_SESSION, WTS_INFO_CLASS::WTS_SESSION, (LPWSTR*)&sessionCount, &sessionId)) { WTS_SESSION_INFO* pSessionInfo = NULL; if (WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pSessionInfo, &sessionCount)) { for (DWORD i = 0; i < sessionCount; i++) { DWORD processCount; if (WTSEnumerateProcesses(pSessionInfo[i].hServer, pSessionInfo[i].SessionId, 1, (PWTS_PROCESS_INFO*)&processCount)) { WTS_PROCESS_INFO* pProcessInfo = NULL; if (WTSEnumerateProcesses(pSessionInfo[i].hServer, pSessionInfo[i].SessionId, 1, &pProcessInfo, &processCount)) { for (DWORD j = 0; j < processCount; j++) { if (pProcessInfo[j].SessionId != sessionId && wcsstr(pProcessInfo[j].pProcessName, qApp->applicationName().toStdWString().c_str())) { HANDLE hProcess = ::OpenProcess(PROCESS_TERMINATE, FALSE, pProcessInfo[j].ProcessId); if (hProcess) { ::TerminateProcess(hProcess, 0); ::CloseHandle(hProcess); } } } ::WTSFreeMemory(pProcessInfo); } } } ::WTSFreeMemory(pSessionInfo); } } // 正常执行程序 QApplication a(argc, argv); MainWindow w; w.show(); return a.exec(); } 上面代码会报出 error: 'WTS_CURRENT_SERVER_HANDLE' was not declared in this scope错误,请修复后给我完整代码
好的,根据您提供的代码,我发现需要添加一个头文件 `wtsapi32.h` 来解决该错误。修改后的完整代码如下:
```
#include <windows.h>
#include <wtsapi32.h>
#include <QString>
#include <QMessageBox>
int main(int argc, char *argv[])
{
HANDLE mutex = ::CreateMutex(Q_NULLPTR, true, (LPCWSTR)qApp->applicationName().toStdWString().c_str());
if (GetLastError() == ERROR_ALREADY_EXISTS)
{
QMessageBox waringBox(QMessageBox::Warning, QStringLiteral("警告"), QStringLiteral("当前程序已运行,不能再次运行!"));
waringBox.setButtonText(QMessageBox::Ok, QStringLiteral("确定"));
waringBox.setStandardButtons(QMessageBox::Ok);
waringBox.exec();
::CloseHandle(mutex);
return 0;
}
// 获取当前登录用户的会话ID
DWORD sessionId;
ProcessIdToSessionId(GetCurrentProcessId(), &sessionId);
// 遍历所有用户会话,关闭其他用户会话中的该程序进程
DWORD sessionCount;
if (ProcessIdToSessionId(GetCurrentProcessId(), &sessionId) && WTSQuerySessionInformationW(WTS_CURRENT_SERVER_HANDLE, WTS_CURRENT_SESSION, WTS_INFO_CLASS::WTS_SESSION, (LPWSTR*)&sessionCount, &sessionId))
{
WTS_SESSION_INFO* pSessionInfo = NULL;
if (WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pSessionInfo, &sessionCount))
{
for (DWORD i = 0; i < sessionCount; i++)
{
DWORD processCount;
if (WTSEnumerateProcesses(pSessionInfo[i].hServer, pSessionInfo[i].SessionId, 1, (PWTS_PROCESS_INFO*)&processCount))
{
WTS_PROCESS_INFO* pProcessInfo = NULL;
if (WTSEnumerateProcesses(pSessionInfo[i].hServer, pSessionInfo[i].SessionId, 1, &pProcessInfo, &processCount))
{
for (DWORD j = 0; j < processCount; j++)
{
if (pProcessInfo[j].SessionId != sessionId && wcsstr(pProcessInfo[j].pProcessName, qApp->applicationName().toStdWString().c_str()))
{
HANDLE hProcess = ::OpenProcess(PROCESS_TERMINATE, FALSE, pProcessInfo[j].ProcessId);
if (hProcess)
{
::TerminateProcess(hProcess, 0);
::CloseHandle(hProcess);
}
}
}
::WTSFreeMemory(pProcessInfo);
}
}
}
::WTSFreeMemory(pSessionInfo);
}
}
// 正常执行程序
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
```
需要注意的是,添加了 `wtsapi32.h` 的头文件之后,编译时需要链接该库文件 `wtsapi32.lib`,否则会出现 `LNK2019` 错误。
#include "mainwindow.h" #include <QApplication> #include <windows.h> #include <wtsapi32.h> #pragma comment(lib, "Wtsapi32.lib") int main(int argc, char *argv[]) { QApplication a(argc, argv); HANDLE hToken = NULL; DWORD dwSessionId = WTSGetActiveConsoleSessionId(); if (!WTSQueryUserToken(dwSessionId, &hToken)) { QMessageBox::warning(nullptr, QStringLiteral("错误"), QStringLiteral("获取用户令牌失败!")); return -1; } HANDLE mutex = ::CreateMutex(Q_NULLPTR, true, (LPCWSTR)qApp->applicationName().toStdWString().c_str()); if (GetLastError() == ERROR_ALREADY_EXISTS) { QMessageBox warningBox(QMessageBox::Warning, QStringLiteral("警告"), QStringLiteral("程序[文本数据同步服务端]只能运行一个!")); warningBox.setButtonText(QMessageBox::Ok, QStringLiteral("确定")); warningBox.setStandardButtons(QMessageBox::Ok); warningBox.exec(); ::CloseHandle(mutex); return 0; } else { ::ReleaseMutex(mutex); } STARTUPINFO si; ZeroMemory(&si, sizeof(si)); si.cb = sizeof(si); si.lpDesktop = (LPWSTR)L"winsta0\\default"; PROCESS_INFORMATION pi; ZeroMemory(&pi, sizeof(pi)); if (!CreateProcessAsUser(hToken, NULL, (LPWSTR)qApp->applicationFilePath().toStdWString().data(), NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi)) { QMessageBox::warning(nullptr, QStringLiteral("错误"), QStringLiteral("创建进程失败!")); CloseHandle(hToken); return -1; } CloseHandle(hToken); MainWindow w; w.show(); return a.exec(); } 以上QT C++代码会报出以下错误: D:\QtProject\DataServer\main.cpp:-1: error: undefined reference to `WTSQueryUserToken@8' collect2.exe:-1: error: error: ld returned 1 exit status 请修复后给我完整代码
#include "mainwindow.h"
#include <QApplication>
#include <windows.h>
#include <wtsapi32.h>
#pragma comment(lib, "Wtsapi32.lib")
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
HANDLE hToken = NULL;
DWORD dwSessionId = WTSGetActiveConsoleSessionId();
if (!WTSQueryUserToken(dwSessionId, &hToken)) {
QMessageBox::warning(nullptr, QStringLiteral("错误"), QStringLiteral("获取用户令牌失败!"));
return -1;
}
HANDLE mutex = ::CreateMutex(Q_NULLPTR, true, (LPCWSTR)qApp->applicationName().toStdWString().c_str());
if (GetLastError() == ERROR_ALREADY_EXISTS) {
QMessageBox warningBox(QMessageBox::Warning, QStringLiteral("警告"), QStringLiteral("程序[文本数据同步服务端]只能运行一个!"));
warningBox.setButtonText(QMessageBox::Ok, QStringLiteral("确定"));
warningBox.setStandardButtons(QMessageBox::Ok);
warningBox.exec();
::CloseHandle(mutex);
return 0;
}
else {
::ReleaseMutex(mutex);
}
STARTUPINFO si;
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
si.lpDesktop = (LPWSTR)L"winsta0\\default";
PROCESS_INFORMATION pi;
ZeroMemory(&pi, sizeof(pi));
if (!CreateProcessAsUser(hToken, NULL, (LPWSTR)qApp->applicationFilePath().toStdWString().data(), NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi)) {
QMessageBox::warning(nullptr, QStringLiteral("错误"), QStringLiteral("创建进程失败!"));
CloseHandle(hToken);
return -1;
}
CloseHandle(hToken);
MainWindow w;
w.show();
return a.exec();
}
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