thread questions

"Lisa Pearlson" <no@spam.plz>
Sun, 25 Jan 2009 06:29:58 +0100
Hi all,

Imagine I need a function that does a lengthy search.
For this function not to block, it should be implemented to be asynchronous.

I guess this would be implemented this way:

DWORD WINAPI DoSearch(LPVOID lpParameter)
    // do some length search here
    return 0;

HANDLE DoSearch(LPCTSTR lpszSubject)
    return CreateProcess(... SearchProc ...);

I want the ability to have multiple simultaneous searches, e.g.:

HANDLE hSearch1 = DoSearch(_T("Search 1"));
HANDLE hSearch2 = DoSearch(_T("Search 2"));

I could wait for a search to complete this way:

WaitForSingleObject(hSearch1, INFINITE); // wait for completion
CloseHandle(hSearch1); // cleanup

So far, so good...
Now I would like the ability to ABORT the thread, by simply performing a

CloseHandle(hSearch2); // abort second search

Normally, I use some event handle or global BOOL value, and pass that to
thread, eg:
BOOL g_bAbort = FALSE;

DWORD WINAPI ThreadProc(LPVOID lpParameter)
    LPBOOL pBool = (LPBOOL) lpParameter;
    while (!pBool) {
        // do something
    return 0;

However, this requires a global variable, .. and that complicates the
ability to run copies of the function simultanously (I reckon it requires a
global list that dynamically allocates data to hold reference to each
thread).. I wonder if there is an easy way.

In particular, I am wondering if a thread can be made to abort as soon as
all handles to it have been closed, eg:
CloseHandle(hSearch2); // should abort the thread

Is it possible for a thread to be aware of handles to itself having been

I assume this can not work:

I assume this will not work:

DWORD WINAPI SomeFunc(LPVOID lpParameter)
    HANDLE hThread = *(HANDLE*) lpParameter; // will this code execute
BEFORE the local variable in caller is destroyed???
    while (<handle is valid>) // what function can be used to know if handle
hasn't been closed by caller? GetHandleInformation?
        // do something
    return 0;

int main(...)
    HANDLE hThread; // local variable
    hThread = CreateThread(... SomeFunc, &hThread, ...);

I hope my lengthy e-mail is clear.. and that someone will be so kind to
answer each of my questions.

Thanks in advance,

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