util: set os-level thread names on Windows #35884

pull ViniciusCestarii wants to merge 1 commits into bitcoin:master from ViniciusCestarii:name-windows-os-thread changing 1 files +9 −0

ViniciusCestarii commented at 6:41 PM on August 4, 2026: contributor

Update SetThreadName to set os-level thread names on Windows too.

This is useful for debugging-ergonomics on Windows. Threads currently show up unnamed in debuggers, crash dumps on Windows and mismatch what's documented under https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#threads.

Tested with the mingw cross build running on Windows 11, print from WinDbg:

<img width="713" height="631" alt="image" src="https://github.com/user-attachments/assets/05e03383-c9b1-4e6b-91f3-9088b2fc7e90" />
DrahtBot added the label Utils/log/libs on Aug 4, 2026
DrahtBot commented at 6:41 PM on August 4, 2026: contributor



The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.



Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35884.



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Type Reviewers

ACK hebasto, l0rinc, winterrdog

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l0rinc commented at 6:45 PM on August 4, 2026: contributor

Concept ACK
maflcko commented at 8:20 AM on August 18, 2026: member

Should netbsd be supported as well?
in src/util/threadnames.cpp:22 in d04e650169
```
  17 | @@ -18,6 +18,10 @@
  18 |  #include <sys/prctl.h>
  19 |  #endif
  20 |  
  21 | +#ifdef WIN32
  22 | +#include <windows.h>
```
hebasto commented at 10:37 AM on August 18, 2026:

Why not <processthreadsapi.h>?

ViniciusCestarii commented at 1:17 PM on August 18, 2026:

Good point, switched to <processthreadsapi.h> on 531768ab8cfcc2b73afd969fe590c19247d42d6e.
ViniciusCestarii commented at 2:46 PM on August 18, 2026:

CI failed:

C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um\winnt.h(169,1): error C1189: #error: "No Target Architecture" [D:\a\bitcoin\bitcoin\build\src\util\bitcoin_util.vcxproj]

I will take a look at it.
ViniciusCestarii commented at 5:57 PM on August 18, 2026:

I reproduced it in my Windows 11 machine and have found that MSVC processthreadsapi.h insn't self contained and only the windows.h set the architecture flag for it. So I will revert back to include windows.h to work on MSVC build.
in src/util/threadnames.cpp:37 in d04e650169
```
  32 | @@ -29,6 +33,10 @@ static void SetThreadName(const char* name)
  33 |      pthread_set_name_np(pthread_self(), name);
  34 |  #elif defined(__APPLE__)
  35 |      pthread_setname_np(name);
  36 | +#elif defined(WIN32)
  37 | +    // Thread names are ASCII-only, so widening each character is sufficient.
```
hebasto commented at 10:42 AM on August 18, 2026:

Could you please clarify the comment? "... is sufficient" for what?

ViniciusCestarii commented at 1:18 PM on August 18, 2026:

Sufficient as a conversion to UTF-16. SetThreadDescription takes a PCWSTR, and in general converting const char* to wchar_t* needs to know the source encoding, since non-ASCII bytes are multibyte sequences that a per-character widening would mangle. All thread names here are hardcoded ASCII literals and maps 1:1 onto the same UTF-16 code unit, which means the std::wstring construction is correct and MultiByteToWideChar isn't needed.

Updated comment on 531768ab8cfcc2b73afd969fe590c19247d42d6e so it explains better.

hebasto commented at 1:37 PM on August 18, 2026:

Is this still needed after #32380?

ViniciusCestarii commented at 2:25 PM on August 18, 2026:

I didn't know there were -A variants, pretty nice.

I searched for the -A version of SetThreadDescription but I found no variant, windows api documentation states no variant for SetThreadDescription (req.unicode-ansi is empty). So it is needed.
ViniciusCestarii force-pushed on Aug 18, 2026
ViniciusCestarii commented at 1:21 PM on August 18, 2026: contributor

Thanks for the reviews! Forced-push 531768ab8cfcc2b73afd969fe590c19247d42d6e to include <processthreadsapi.h> instead of <windows.h> and also updated comment on std::wstring construction to explain better why it is sufficient to convert thread name to UTF-16 and doens't need MultiByteToWideChar.
ViniciusCestarii commented at 1:34 PM on August 18, 2026: contributor

Should netbsd be supported as well?

IMO it should since it is a supported build target.
DrahtBot added the label CI failed on Aug 18, 2026
util: set os-level thread names on Windows dd669f40b9
ViniciusCestarii force-pushed on Aug 18, 2026
ViniciusCestarii commented at 6:01 PM on August 18, 2026: contributor

Forced push dd669f40b98bb864bb9713673f0c38d946040591 to include <windows.h> back, since <processthreadsapi.h> isn't self contained for MSVC build.
DrahtBot removed the label CI failed on Aug 18, 2026
hebasto approved
hebasto commented at 3:58 PM on August 20, 2026: member

ACK dd669f40b98bb864bb9713673f0c38d946040591, tested Guix-built bitcoind.exe on Windows 11 Pro using WinDbg:

<img width="578" height="659" alt="Image" src="https://github.com/user-attachments/assets/4976b474-6235-4f91-b83a-b4048b61fa86" />
DrahtBot requested review from l0rinc on Aug 20, 2026
l0rinc commented at 5:11 PM on August 20, 2026: contributor

code review ACK dd669f40b98bb864bb9713673f0c38d946040591
winterrdog commented at 6:08 PM on August 20, 2026: contributor

utACK dd669f40b98bb864bb9713673f0c38d946040591
fanquake merged this on Aug 21, 2026
fanquake closed this on Aug 21, 2026

Type	Reviewers
ACK	hebasto, l0rinc, winterrdog

hebasto commented at 8:52 AM on August 22, 2026: member

Build fails on Ubuntu 24.04:

/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/src/util/threadnames.cpp: In function ‘void SetThreadName(const char*)’:
/home/runner/work/bitcoin-core-nightly/bitcoin-core-nightly/src/util/threadnames.cpp:40:7: error: ‘::SetThreadDescription’ has not been declared; did you mean ‘SetThreadInformation’?
   40 |     ::SetThreadDescription(::GetCurrentThread(), wname.c_str());
      |       ^~~~~~~~~~~~~~~~~~~~
      |       SetThreadInformation
gmake[2]: *** [src/util/CMakeFiles/bitcoin_util.dir/build.make:440: src/util/CMakeFiles/bitcoin_util.dir/threadnames.cpp.obj] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:1416: src/util/CMakeFiles/bitcoin_util.dir/all] Error 2

in src/util/threadnames.cpp:40 in dd669f40b9

  32 | @@ -29,6 +33,11 @@ static void SetThreadName(const char* name)
  33 |      pthread_set_name_np(pthread_self(), name);
  34 |  #elif defined(__APPLE__)
  35 |      pthread_setname_np(name);
  36 | +#elif defined(WIN32)
  37 | +    // Thread names are ASCII-only, so widening each character is sufficient as
  38 | +    // a conversion to UTF-16.
  39 | +    const std::wstring wname{name, name + std::strlen(name)};
  40 | +    ::SetThreadDescription(::GetCurrentThread(), wname.c_str());

hebasto commented at 9:06 AM on August 22, 2026:

Apparently, SetThreadDescription is only available in MinGW-w64 >= 12.0.

See https://github.com/mingw-w64/mingw-w64/commit/3a137bd87ea83d174f4a225568b75cabdbc70852.

hebasto commented at 9:13 AM on August 22, 2026: member

@maflcko @fanquake

Should we document the MinGW-w64 minimum required version and / or revert this change?
ViniciusCestarii commented at 2:20 PM on August 22, 2026: contributor

Opened #36057, which checks for the symbol at configure time so older mingw-w64 builds fine.

Happy to document a minimum or revert instead if that's preferred.

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l0rinc

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#36057 build: check for SetThreadDescription() at configure time

util: set os-level thread names on Windows #35884

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