Revert #36057 & document mingw-w64 requirement #36271

fanquake commented at 12:36 PM on September 16, 2026: member

A follow-up reverting #36057, now that we've branched off for 33.x. Also documents mingw-w64 requirements (#32380).

DrahtBot commented at 12:36 PM on September 16, 2026: contributor

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

External sites

Code coverage & benchmarks: https://corecheck.dev/bitcoin/bitcoin/pulls/36271
Ralph review <img src=https://review.fish.foo/assets/bitcoin/bitcoin/36271.png alt="Ralph review status"> https://git.fish.foo/bitcoin/bitcoin/pulls/36271#author-ralph

Reviews

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Type	Reviewers
ACK	willcl-ark, hebasto
Stale ACK	ViniciusCestarii, hodlinator

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Conflicts

Reviewers, this pull request conflicts with the following ones:

#36042 <sub><img src="https://drahtbot.space/ack_count/bitcoin/bitcoin/36042.svg"></sub> (build: Bump g++ minimum supported version to 13 by maflcko)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

fanquake force-pushed on Sep 16, 2026

in depends/README.md:170 in bc63b06914

 166 | @@ -167,7 +167,6 @@ Some Ubuntu or Debian versions may not offer a working package. In this case,
 167 |  you may install `nix-bin` and use the Nix shell from the repository root:
 168 |  
 169 |      apt install nix-bin
 170 | -    NIX_BUILD_SHELL=bash HOST=x86_64-w64-mingw32 nix-shell contrib/devtools/shell-win64-cross.nix  # MSVCRT
 171 |      NIX_BUILD_SHELL=bash HOST=x86_64-w64-mingw32ucrt nix-shell contrib/devtools/shell-win64-cross.nix  # UCRT

maflcko commented at 2:01 PM on September 16, 2026:

I think this one can be removed as well now:

diff --git a/contrib/devtools/shell-win64-cross.nix b/contrib/devtools/shell-win64-cross.nix
index 4fd83b0..7e0da92 100644
--- a/contrib/devtools/shell-win64-cross.nix
+++ b/contrib/devtools/shell-win64-cross.nix
@@ -10,8 +10,3 @@
 let
-  host = builtins.getEnv "HOST";
-  crossPkgs = if host == "x86_64-w64-mingw32ucrt"
-    then pkgs.pkgsCross.ucrt64
-    else if host == "x86_64-w64-mingw32"
-      then pkgs.pkgsCross.mingwW64
-      else throw "Unsupported HOST: ${host}";
+  crossPkgs = pkgs.pkgsCross.ucrt64;
   toolchain = crossPkgs.stdenv.cc.targetPrefix;
diff --git a/depends/README.md b/depends/README.md
index 3cee78a..f17bcab 100644
--- a/depends/README.md
+++ b/depends/README.md
@@ -169,4 +169,3 @@ you may install `nix-bin` and use the Nix shell from the repository root:
     apt install nix-bin
-    NIX_BUILD_SHELL=bash HOST=x86_64-w64-mingw32ucrt nix-shell contrib/devtools/shell-win64-cross.nix  # UCRT
+    NIX_BUILD_SHELL=bash nix-shell contrib/devtools/shell-win64-cross.nix

fanquake commented at 2:07 PM on September 16, 2026:

Sure, dropped.

fanquake force-pushed on Sep 16, 2026

DrahtBot added the label CI failed on Sep 16, 2026

DrahtBot removed the label CI failed on Sep 16, 2026

hebasto commented at 5:07 PM on September 16, 2026: member

Concept ACK. This follows the plan.

ViniciusCestarii commented at 7:28 PM on September 16, 2026: contributor

ACK ce76c082cead6a107d1c95f584a0eff390b3539f

DrahtBot requested review from hebasto on Sep 16, 2026

in src/util/threadnames.cpp:36 in ce76c082ce outdated

  32 | @@ -35,7 +33,7 @@ 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(HAVE_SETTHREADDESCRIPTION)
  37 | +#elif defined(WIN32)

hodlinator commented at 11:53 AM on September 21, 2026:

One could potentially retain the HAVE_SETTHREADDESCRIPTION logic and make it fail at compile time:

#if defined(WIN32) && !defined(HAVE_SETTHREADDESCRIPTION)
#error "At least Mingw-w64 version 12.0 is required."
#endif

But I'm okay with just documenting the minimum version as well, and dropping HAVE_SETTHREADDESCRIPTION to keep build complexity down.

hodlinator approved

hodlinator commented at 12:21 PM on September 21, 2026: contributor

ACK ce76c082cead6a107d1c95f584a0eff390b3539f

Makes sense to drop remaining MSVCRT logic now that #33593 was merged.

Only remaining but probably acceptable references to "MSVCRT" in the repo are now overriding to UCRT:

https://github.com/bitcoin/bitcoin/blob/ce76c082cead6a107d1c95f584a0eff390b3539f/contrib/guix/manifest_build.scm#L130-L139

Completed Linux->Windows cross CI locally:

env -i HOME="$HOME" PATH="$PATH" USER="$USER" bash -c 'MAKEJOBS="-j$(nproc)" FILE_ENV="./ci/test/00_setup_env_win64.sh" ./ci/test_run_all.sh'

(test_run_all.sh calls 02_run_container.py which calls shell-win64-cross.nix since 00_setup_env_win64.sh set HOST=x86_64-w64-mingw32ucrt).

maflcko added this to the milestone 33.0 on Sep 21, 2026

hebasto approved

hebasto commented at 9:23 PM on September 22, 2026: member

ACK ce76c082cead6a107d1c95f584a0eff390b3539f, I have reviewed the code and it looks OK.

However, I'd like to leave a couple of thoughts regarding versioning of the Windows cross-build toolchain.

The MinGW-w64 version should be logged in the configure summary, along with the compiler version. See the proposal in #36029.
Historically, we were bound to whichever combination of MinGW-w64 and GCC a particular distribution shipped. Switching to Nix opens the door to testing every documented combination (with some patching).

So I tried MinGW-w64 12.0.0 + GCC 12.4.0:
- The wallet_migration.py test fails. ~I haven't looked into it yet, but it may be a reason to bump the minimum supported MinGW-w64 version to 13.0, which contains many bug fixes.~
- Requiring GCC 13 or newer for the GUI appears unnecessary. Perhaps I misjudged the minimum toolchain requirements in 0a6724aaae973659b6c44eb5a062aaaaf57be870.

hebasto commented at 11:00 AM on September 23, 2026: member

The wallet_migration.py test fails.

This turned out to be a libstdc++ bug. It was fixed on master (GCC 15.1) and backported to GCC 14 (https://github.com/gcc-mirror/gcc/commit/35c98149a5c7af9159fa7615d8d827b3aaa3cc97, first in GCC 14.3.0) and GCC 13 (https://github.com/gcc-mirror/gcc/commit/8b3e47b4099f319e38d357f7c646f51040a13d6e, first in GCC 13.4.0).

GCC 12 never received the backport, so every 12.x release remains broken.

I believe we should handle these cases somehow.

maflcko commented at 11:38 AM on September 23, 2026: member

I believe we should handle these cases somehow.

See #36042, but there could also be a unit test, if you think it is important?

DrahtBot added the label Needs rebase on Sep 24, 2026

fanquake force-pushed on Sep 25, 2026

DrahtBot added the label CI failed on Sep 25, 2026

DrahtBot removed the label CI failed on Sep 25, 2026

DrahtBot removed the label Needs rebase on Sep 25, 2026

fanquake requested review from hebasto on Sep 29, 2026

fanquake force-pushed on Oct 2, 2026

hebasto approved

hebasto commented at 4:29 PM on October 2, 2026: member

ACK b6eebe027eb59a7cafc3814b48658708bbc4b8e2.

DrahtBot requested review from ViniciusCestarii on Oct 2, 2026

DrahtBot requested review from hodlinator on Oct 2, 2026

Revert "build: check for SetThreadDescription() at configure time"

This reverts commit bed46bd16c2b34eec62849b96cebbbdbcdd2c1ac.

8073ff101f

doc: document mingw-w64 requirement in Windows build docs cd7605a6b7

nix: drop MSVCRT build 1c96b08cb6

in contrib/devtools/shell-win64-cross.nix:12 in b6eebe027e

  13 | -    then pkgs.pkgsCross.ucrt64
  14 | -    else if host == "x86_64-w64-mingw32"
  15 | -      then pkgs.pkgsCross.mingwW64
  16 | -      else throw "Unsupported HOST: ${host}";
  17 | +  baseCrossPkgs = pkgs.pkgsCross.ucrt64;
  18 |    crossPkgs = baseCrossPkgs.extend (_: _: {

willcl-ark commented at 9:02 PM on October 2, 2026:

In b6eebe027eb59a7cafc3814b48658708bbc4b8e2

I think this slight simplification should work too, if you retouch:

  crossPkgs = pkgs.pkgsCross.ucrt64.extend (_: _: {

fanquake commented at 10:12 AM on October 3, 2026:

Thanks, taken.

fanquake force-pushed on Oct 3, 2026

DrahtBot added the label CI failed on Oct 3, 2026

DrahtBot removed the label CI failed on Oct 3, 2026

willcl-ark approved

willcl-ark commented at 9:19 AM on October 5, 2026: member

utACK 1c96b08cb60bee930ed390de019a2cf943445ef5

If i have it all correct, after this PR:

our Windows cross-build CI, Guix release builds, and Nix shell use UCRT.
MinGW-w64 12 itself still supports both UCRT and MSVCRT. the version requirement does not force any runtime choice on native windows builders.
our documented cross-build instructions use UCRT, while native MinGW-w64 builds are not officially tested.

DrahtBot requested review from hebasto on Oct 5, 2026

hebasto approved

hebasto commented at 7:03 AM on October 11, 2026: member

re-ACK 1c96b08cb60bee930ed390de019a2cf943445ef5.

hebasto merged this on Oct 11, 2026

hebasto closed this on Oct 11, 2026

fanquake deleted the branch on Oct 11, 2026