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Verify primary PID is still alive before assuming it is running #217

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Verify primary PID is still alive before assuming it is running
chen3feng May 23, 2026
38c4cef
Merge branch 'master' into master
itay-grudev May 26, 2026
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34 changes: 34 additions & 0 deletions singleapplication.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,9 +26,36 @@
#include <QtCore/QByteArray>
#include <QtCore/QSharedMemory>

#ifdef Q_OS_UNIX
#include <signal.h>
#include <errno.h>
#endif
#ifdef Q_OS_WIN
#include <windows.h>
#endif

#include "singleapplication.h"
#include "singleapplication_p.h"

static bool isProcessRunning( qint64 pid )
{
if ( pid <= 0 )
return false;

#ifdef Q_OS_UNIX
return kill( static_cast<pid_t>( pid ), 0 ) == 0 || errno != ESRCH;
#endif
#ifdef Q_OS_WIN
HANDLE hProcess = OpenProcess( PROCESS_QUERY_LIMITED_INFORMATION, FALSE, static_cast<DWORD>( pid ) );
if ( hProcess == NULL )
return false;
DWORD exitCode;
bool running = GetExitCodeProcess( hProcess, &exitCode ) && exitCode == STILL_ACTIVE;
CloseHandle( hProcess );
return running;
#endif
}

/**
* @brief Constructor. Checks and fires up LocalServer or closes the program
* if another instance already exists
Expand Down Expand Up @@ -138,6 +165,13 @@ SingleApplication::SingleApplication( int &argc, char *argv[], bool allowSeconda
}
}

// If the recorded primary PID is no longer running (e.g. force-killed),
// take over as the primary instance
if( inst->primary && !isProcessRunning( inst->primaryPid ) ){
qWarning() << "SingleApplication: Primary instance (PID" << inst->primaryPid << ") is no longer running. Taking over.";
d->initializeMemoryBlock();
}

if( inst->primary == false ){
d->startPrimary();
if( ! d->memory->unlock() ){
Expand Down
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