SemWaitableEvent.cpp

/*
 * Copyright(c) Sophist Solutions, Inc. 1990-2025.  All rights reserved
 */
#include "Stroika/Foundation/StroikaPreComp.h"
 
#include <unistd.h>
 
#include "Stroika/Foundation/Execution/Exceptions.h"
 
#include "SemWaitableEvent.h"
 
using namespace Stroika::Foundation;
using namespace Stroika::Foundation::Execution;
using namespace Stroika::Foundation::Execution::Platform::POSIX;
 
// Comment this in to turn on aggressive noisy DbgTrace in this module
//#define   USE_NOISY_TRACE_IN_THIS_MODULE_       1
 
/*
 ********************************************************************************
 ************* Execution::Platform::POSIX::SemWaitableEvent *********************
 ********************************************************************************
 */
SemWaitableEvent::SemWaitableEvent ()
{
    [[maybe_unused]] constexpr int kpshared     = 0; // shared between threads of a process
    int                            defaultValue = 0;
#if qCompilerAndStdLib_unnamed_semaphores_Buggy
    char nameBuf[1000] = "/tmp/semaphore-XXXXXX";
    ::close (::mkstemp (nameBuf)); // create file as side-effect so no race - file name still reserved by this CTOR
    Verify ((fSem_ = ::sem_open (nameBuf, O_CREAT, S_IRWXU | S_IRWXG, defaultValue)) != SEM_FAILED);
    Verify (::sem_unlink (nameBuf) == 0);
#else
    Verify (::sem_init (&fSem_, kpshared, defaultValue) == 0);
#endif
}
 
SemWaitableEvent::~SemWaitableEvent ()
{
#if qCompilerAndStdLib_unnamed_semaphores_Buggy
    Verify (::sem_close (fSem_) == 0);
#else
    Verify (::sem_destroy (&fSem_) == 0);
#endif
}
 
void SemWaitableEvent::Wait ()
{
#if qCompilerAndStdLib_unnamed_semaphores_Buggy
    sem_t* pSem = fSem_;
#else
    sem_t* pSem = &fSem_;
#endif
    int s{};
    while ((s = ::sem_wait (pSem)) == -1 && errno == EINTR) {
        continue; /* Restart if interrupted by handler */
    }
    Execution::ThrowPOSIXErrNoIfNegative (s);
}
 
// use no_sanitize(thread) to workaround http://stroika-bugs.sophists.com/browse/STK-677
Stroika_Foundation_Debug_ATTRIBUTE_NO_SANITIZE_THREAD void SemWaitableEvent::Set ()
{
#if qCompilerAndStdLib_unnamed_semaphores_Buggy
    sem_t* pSem = fSem_;
#else
    sem_t* pSem = &fSem_;
#endif
    // see http://stroika-bugs.sophists.com/browse/STK-677 - save/restore errno so this doesn't spoil errno if called from signal handler
    errno_t saved = errno;
    Verify (::sem_post (pSem) == 0);
    errno = saved;
}