Enumerating threads in Windows

Question

How can I enumerate all of the threads in a process given a HANDLE to the process (or a process ID)? I'm interested in doing this so I can further do an EnumThreadWindows on each thread.

Unification

Answer 1

Enumerating threads in a process at MSDN Blogs.

Code snippet from there:

#include <stdio.h>
#include <windows.h>
#include <tlhelp32.h>

int __cdecl main(int argc, char **argv)
{
 HANDLE h = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
 if (h != INVALID_HANDLE_VALUE) {
  THREADENTRY32 te;
  te.dwSize = sizeof(te);
  if (Thread32First(h, &te)) {
   do {
     if (te.dwSize >= FIELD_OFFSET(THREADENTRY32, th32OwnerProcessID) +
                      sizeof(te.th32OwnerProcessID)) {
       printf("Process 0x%04x Thread 0x%04x\n",
             te.th32OwnerProcessID, te.th32ThreadID);
     }
   te.dwSize = sizeof(te);
   } while (Thread32Next(h, &te));
  }
  CloseHandle(h);
 }
 return 0;
}

Kostman

It's good to list at least the major API functions needed, so that this answer doesn't become completely useless if the link breaks (MSDN has a habit of changing URLs) – Cultus

MSDN Blog link broke. Now at devblogs.microsoft.com/oldnewthing/20060223-14/?p=32173 ; formatting of that post is ugly now unfortunately, which is a shame. – Cesena

Answer 2

The ToolHelp library gives an API for snapshotting processes and enumerating their threads (amongst other properties). See MSDN for details.

Path

Answer 3

// returns the tid of threads in a given process pid. it is recursive and called from a while loop.
// return 0 when there are no more threads.

DWORD EnumerateThreads(DWORD pid)
{// needs working for a simpler loop
    char szText[MAX_PATH];

    static BOOL bStarted;
    static HANDLE hSnapPro, hSnapThread;
    static LPPROCESSENTRY32 ppe32;
    static PTHREADENTRY32 pte32;


    if (!bStarted)
    {
        if (!bStarted)
        {
            bStarted++;
            pte32 = new THREADENTRY32;
            pte32->dwSize = sizeof(THREADENTRY32);

            hSnapThread = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);

            if (!hSnapThread)
            {
                FormatErrorMessage("GetLastError -> hSnapThread = CreateToolhelp32Snapshot\n", GetLastError());
                delete pte32;
                bStarted = 0;
                return 0;
            }

            if (Thread32First(hSnapThread, pte32))
            {
                do
                {
                    if (pid == pte32->th32OwnerProcessID)
                    {
                        wsprintf(szText, "__yes Thread32First pid: 0x%X - tid: 0x%X\n", pid, pte32->th32ThreadID);
                        OutputDebugString(szText);
                        return pte32->th32ThreadID;
                    }
                } 
                while (Thread32Next(hSnapThread, pte32));
            }
            else
                FormatErrorMessage("GetLastError ->Thread32First\n", GetLastError());
        }
    }

    if (Thread32Next(hSnapThread, pte32))
    {
        do
        {
            if (pid == pte32->th32OwnerProcessID)
            {
                wsprintf(szText, "__yes Thread32First pid: 0x%X - tid: 0x%X\n", pid, pte32->th32ThreadID);
                OutputDebugString(szText);
                return pte32->th32ThreadID;
            }
        }
        while (Thread32Next(hSnapThread, pte32));
    }
    else
        FormatErrorMessage("GetLastError ->Thread32First\n", GetLastError());

    CloseHandle(hSnapThread);
    bStarted = 0;
    delete pte32;

    OutputDebugString("__finished EnumerateThreads\n");

    return 0;
}

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