curl_addrinfo.c error: 'getaddrinfo' undeclared in old-MinGW CI builds

[bagder]

The appveyor CI builds with cmake using Visual Studio 2022 are permafailing since a while back. See log

The compiler errors are:

C:/projects/curl/lib/curl_addrinfo.c: In function 'Curl_getaddrinfo_ex':
C:/projects/curl/lib/curl_addrinfo.c:192:5: error: implicit declaration of function 'freeaddrinfo'; did you mean 'getaddrinfo'? [-Werror=implicit-function-declaration]
  192 |     freeaddrinfo(aihead);
      |     ^~~~~~~~~~~~
      |     getaddrinfo
C:/projects/curl/lib/curl_addrinfo.c:192:5: error: nested extern declaration of 'freeaddrinfo' [-Werror=nested-externs]
C:/projects/curl/lib/curl_addrinfo.c: In function 'curl_dbg_getaddrinfo':
C:/projects/curl/lib/curl_addrinfo.c:556:14: error: 'getaddrinfo' undeclared (first use in this function); did you mean 'addrinfo'?
  556 |   int res = (getaddrinfo)(hostname, service, hints, result);
      |              ^~~~~~~~~~~
      |              addrinfo
C:/projects/curl/lib/curl_addrinfo.c:556:14: note: each undeclared identifier is reported only once for each function it appears in
cc1.exe: all warnings being treated as errors
make[2]: *** [lib/CMakeFiles/libcurl.dir/build.make:242: lib/CMakeFiles/libcurl.dir/curl_addrinfo.c.obj] Error 1

[gvanem]

Looks like a _WIN32_WINNT >= 0x0602 is not set on AppVeyor. But I fail to understand which SDK is used and how CMake uses it.

Edit. From the above log, it seems to use the old SDK under C:\Program Files\Microsoft SDKs\Windows\v7.1.

[mback2k]

Ping @MarcelRaad

[MarcelRaad]

This is the classic MinGW build, which uses MinGW's own SDK and defaults to _WIN32_WINNT = 0x500.
The output clearly says "-- Looking for freeaddrinfo - not found", so we shouldn't try to use it. I haven't investigated yet what broke it.

[MarcelRaad]

8ba22ff removed forcing _WIN32_WINNT to 0x501, which previously made getaddrinfo and freeaddrinfo available for classic MinGW.
But why does

curl/CMakeLists.txt

Line 1069 in d48dd15

check_symbol_exists(getaddrinfo "${CURL_INCLUDES}" HAVE_GETADDRINFO)

set HAVE_GETADDRINFO? The autotools builds correctly determines it to be unavailable, and I currently don't have a CMake setup usable with classic MinGW 😕

[vszakats]

@MarcelRaad: In CMake/Platforms/WindowsCache.cmake there is this:

    if(ENABLE_IPV6)
      set(HAVE_GETADDRINFO 1)
    else()
      set(HAVE_GETADDRINFO 0)
    endif()

Can it be related to this issue?

(Half-guessing, so this may totally be wrong, but this file seems to be offering predefined configuration values for Windows, and for these, the actual test is not performed?)