How to change the name of a thread

Question

I have a server application that uses "a lot" of threads. Without wanting to get into an argument about how many threads it really should be using, it would be nice to be able to see some descriptive text in the debugger "threads" window describing what each one is, without having to click through to it and determine from the context what it is.

They all have the same start address so generally the threads window says something like "thread_base::start" or something similar. I'd like to know if there is an API call or something that allows me to customise that text.

Renfrow

Answer 1

Use SetThreadName

Chandless

Probably worth noting that it works by sending a special exception to the debugger; if a debugger isn't attached to the process at the time you call SetThreadName, the thread won't have a name. And there's no "GetThreadName" to complement. If a thread should know its own name, it needs to store it. – Flaky

Answer 2

Here is the code I use.

This goes in a header file.

#pragma once

#define MS_VC_EXCEPTION 0x406d1388
#pragma warning(disable: 6312)
#pragma warning(disable: 6322)

typedef struct tagTHREADNAME_INFO
{
    DWORD dwType;        // must be 0x1000
    LPCSTR szName;       // pointer to name (in same addr space)
    DWORD dwThreadID;    // thread ID (-1 caller thread)
    DWORD dwFlags;       // reserved for future use, most be zero
} THREADNAME_INFO;

inline
void SetThreadName(DWORD dwThreadID, LPCSTR szThreadName)
{
#ifdef _DEBUG
    THREADNAME_INFO info;
    info.dwType = 0x1000;
    info.szName = szThreadName;
    info.dwThreadID = dwThreadID;
    info.dwFlags = 0;

    __try
    {
        RaiseException(MS_VC_EXCEPTION, 0, sizeof(info) / sizeof(DWORD), (DWORD *)&info);
    }
    __except (EXCEPTION_CONTINUE_EXECUTION)
    {
    }
#else
    dwThreadID;
    szThreadName;
#endif
}

Then I call it like this inside the threads proc.

SetThreadName(GetCurrentThreadId(), "VideoSource Thread");

It is worth noting that this is the exact code that David posted a link to (Thanks! I had forgotten where I got it). I didn't delete this post because I'd like the code to still be available if MSDN decides to reorganize its links (again).

Bauske

out of curiosity, why did you make it a DEBUG only thingie? – Blackburn

Well, it's not the exact version. The MSDN version doesn't vary by _DEBUG. With this code, if you run the release version under a debugger, the threads won't have names. – Flaky

I use the names to identify the threads in the debugger. If I'm not debugging, I d0n't want the overhead or possible attach vector. – Bauske

You can still attach a debugger to a release build, and it is there that you will need all the help you can get – Renfrow

Answer 3

Windows 10 added SetThreadDescription(), on that platform this will be the best method.

Excurrent