Windows 2025 GitHub runner fails to build cURL

[RossPatterson]

The cURL compilation embedded in the HercControl build fails when run on GitHub's "Windows 2025" runner, which is (since 2025-09) selected by runs-on: [windows-latest], as specified in HercControl's ccpp.yaml file. Googling "no non-blocking method was found/used/set" suggests that at least some versions of cURL throw this error when build with gcc-14, which replaced gcc-12 in the Windows 2025 runner.

Here's the error:

2025-10-10T20:08:27.3819371Z FAILED: [code=1] _deps/curl-build/lib/CMakeFiles/libcurl.dir/nonblock.c.obj 
2025-10-10T20:08:27.3942484Z C:\mingw64\bin\cc.exe -DBUILDING_LIBCURL -DCPR_ENABLE_SSL -DCURL_HIDDEN_SYMBOLS -DCURL_STATICLIB -DHAVE_CONFIG_H -D_USRDLL -D_WIN32_WINNT=0x0600 -ID:/a/_temp/build/_deps/curl-src/include -ID:/a/_temp/build/_deps/curl-build/lib/../include -ID:/a/_temp/build/_deps/curl-src/lib/.. -ID:/a/_temp/build/_deps/curl-src/lib/../include -ID:/a/_temp/build/_deps/curl-build/lib/.. -ID:/a/_temp/build/_deps/curl-src/lib -ID:/a/_temp/build/_deps/curl-build/lib -pedantic -Wall -W -Wpointer-arith -Wwrite-strings -Wunused -Wshadow -Winline -Wnested-externs -Wmissing-declarations -Wmissing-prototypes -Wfloat-equal -Wsign-compare -Wundef -Wendif-labels -Wstrict-prototypes -Wdeclaration-after-statement -Wstrict-aliasing=3 -Wcast-align -Wtype-limits -Wold-style-declaration -Wmissing-parameter-type -Wempty-body -Wclobbered -Wignored-qualifiers -Wconversion -Wvla -Wdouble-promotion -Wno-long-long -Wno-multichar -Wno-format-nonliteral -Wno-sign-conversion -Wno-system-headers -Wno-pedantic-ms-format -Os -DNDEBUG -fvisibility=hidden -MD -MT _deps/curl-build/lib/CMakeFiles/libcurl.dir/nonblock.c.obj -MF _deps\curl-build\lib\CMakeFiles\libcurl.dir\nonblock.c.obj.d -o _deps/curl-build/lib/CMakeFiles/libcurl.dir/nonblock.c.obj -c D:/a/_temp/build/_deps/curl-src/lib/nonblock.c
2025-10-10T20:08:27.4023334Z D:/a/_temp/build/_deps/curl-src/lib/nonblock.c: In function 'curlx_nonblock':
2025-10-10T20:08:27.4182436Z ##[error]D:/a/_temp/build/_deps/curl-src/lib/nonblock.c:83:4: error: #error "no non-blocking method was found/used/set"
2025-10-10T20:08:27.4273336Z    83 | #  error "no non-blocking method was found/used/set"
2025-10-10T20:08:27.4300246Z       |    ^~~~~
2025-10-10T20:08:27.4361915Z ##[warning]D:/a/_temp/build/_deps/curl-src/lib/nonblock.c:47:34: warning: unused parameter 'sockfd' [-Wunused-parameter]
2025-10-10T20:08:27.4524178Z    47 | int curlx_nonblock(curl_socket_t sockfd,    /* operate on this */
2025-10-10T20:08:27.4594770Z       |                    ~~~~~~~~~~~~~~^~~~~~
2025-10-10T20:08:27.4636963Z ##[warning]D:/a/_temp/build/_deps/curl-src/lib/nonblock.c:48:24: warning: unused parameter 'nonblock' [-Wunused-parameter]
2025-10-10T20:08:27.4692928Z    48 |                    int nonblock   /* TRUE or FALSE */)
2025-10-10T20:08:27.4908688Z       |                    ~~~~^~~~~~~~
2025-10-10T20:08:27.4954695Z ##[warning]D:/a/_temp/build/_deps/curl-src/lib/nonblock.c:85:1: warning: control reaches end of non-void function [-Wreturn-type]
2025-10-10T20:08:27.4989085Z    85 | }
2025-10-10T20:08:27.5048554Z       | ^

[RossPatterson]

Fix is available, but needs PR #3 to be merged first.

[RossPatterson]

It turns out that the cURL build is being done by the libcpr submodule, which is locked to a commit from 2021-12-09 (beb9e98806bb84bcc130a2cebfbcbbc6ce62b335). The underlying bug was fixed in cURL on 2024-05-10 and released in cURL 8.8.0 on 2024-05-22. libcpr updated its built-in cURL version to 8.10 on 2022-09-22.

Updating the cpr submodule to at least that commit should resolve this issue. My workaround was simply to use the "windows 2022" runner, which doesn't have gcc-14.

[RossPatterson]

:sigh: My workaround now fails. GitHub updated the Windows 2022 runner to use gcc 14 on 2025-10-25. I didn't want to update libcpr for this, but it's clear I have to try.

[RossPatterson]

I didn't want to update libcpr for this, but it's clear I have to try.

Aaannnddd ... this is why.

• I updated to just the commit I thought I needed. But the libcpr CMake setup failed on all platforms with "Error: cpr 1.11.0 does not support 14. Please use cpr <= 1.9.x".
• Checking libcpr's releases, the latest 1.9.x release is 1.9.8, so I updated to 1.9.8's commit (3591f20e82338d0a21733045f59accd2d476d84f). It builds fine for Ubuntu and Windows, but MacOS failed to link the compiled code with "ld: library 'idn2' not found".