https://bugs.exim.org/show_bug.cgi?id=2377
Giuseppe D'Angelo <dangelog@???> changed:
What |Removed |Added
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CC| |dangelog@???
--- Comment #2 from Giuseppe D'Angelo <dangelog@???> ---
What's the minimum Windows version that PCRE wants to support?
On Windows 7, it's fairly easy using the INIT_ONCE family of functions, for
instance as described here:
https://docs.microsoft.com/it-it/windows/desktop/Sync/using-one-time-initialization
So possibly something like this (just written here, not tested...):
static HANDLE global_mutex = 0;
static INIT_ONCE global_mutex_once = INIT_ONCE_STATIC_INIT;
static BOOL CALLBACK sljit_grab_lock_initialize(PINIT_ONCE, PVOID, PVOID *) {
global_mutex = CreateMutex(NULL, TRUE, NULL);
return TRUE;
}
And change sljit_grab_lock to do
{
if (!InitOnceExecuteOnce(&global_mutex_once, sljit_grab_lock_initialize,
NULL, NULL))
/* OS failure. abort()? */
WaitForSingleObject(global_mutex, INFINITE);
}
If you also need to support earlier versions of Windows, then one has to use
the Interlocked API:
https://docs.microsoft.com/en-us/windows/desktop/sync/interlocked-variable-access
Basically using the fact that HANDLE is a PVOID. So (again, pseudocode):
static volatile HANDLE global_mutex = 0;
SLJIT_API_FUNC_ATTRIBUTE void SLJIT_FUNC sljit_grab_lock(void) {
if (!global_mutex) { // this read is atomic on Windows
HANDLE mutex = CreateMutex(NULL, TRUE, NULL);
if (InterlockedCompareExchangePointer(&global_mutex, mutex, NULL) != NULL)
{
// some other thread got there first
CloseHandle(mutex);
}
}
WaitForSingleObject(global_mutex, INFINITE);
}
Hope this helps.
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