CMake: support specifying the target Windows version

Previously, it was only possible to set it to Windows Vista or XP by
setting the option `ENABLE_INET_PTON` to `ON` resp. `OFF`.
Use a new cache variable `CURL_TARGET_WINDOWS_VERSION` to be able to
explicitly set the target Windows version. `ENABLE_INET_PTON` is
ignored in this case.

Ref: https://github.com/curl/curl/pull/1639#issuecomment-313039352
Ref: https://github.com/curl/curl/pull/4607#issuecomment-557541456
Closes https://github.com/curl/curl/pull/4815

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 649db52a649cbb1875b6f27210dbdc4e031954a3..432837c5a8ed66733c4028adb02151dd5d85ccc4 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,6 +79,16 @@ option(ENABLE_ARES "Set to ON to enable c-ares support" OFF)
 if(WIN32)
   option(CURL_STATIC_CRT "Set to ON to build libcurl with static CRT on Windows (/MT)." OFF)
   option(ENABLE_INET_PTON "Set to OFF to prevent usage of inet_pton when building against modern SDKs while still requiring compatibility with older Windows versions, such as Windows XP, Windows Server 2003 etc." ON)
+  set(CURL_TARGET_WINDOWS_VERSION "" CACHE STRING "Minimum target Windows version as hex string")
+  if(CURL_TARGET_WINDOWS_VERSION)
+    add_definitions(-D_WIN32_WINNT=${CURL_TARGET_WINDOWS_VERSION})
+  elseif(ENABLE_INET_PTON)
+    # _WIN32_WINNT_VISTA (0x0600)
+    add_definitions(-D_WIN32_WINNT=0x0600)
+  else()
+    # _WIN32_WINNT_WINXP (0x0501)
+    add_definitions(-D_WIN32_WINNT=0x0501)
+  endif()
 endif()
 option(CURL_LTO "Turn on compiler Link Time Optimizations" OFF)
 
@@ -858,16 +868,6 @@ elseif(HAVE_LIBSOCKET)
   set(CMAKE_REQUIRED_LIBRARIES socket)
 endif()
 
-if(WIN32)
-  if(ENABLE_INET_PTON)
-    # _WIN32_WINNT_VISTA (0x0600)
-    add_definitions(-D_WIN32_WINNT=0x0600)
-  else()
-    # _WIN32_WINNT_WINXP (0x0501)
-    add_definitions(-D_WIN32_WINNT=0x0501)
-  endif()
-endif()
-
 check_symbol_exists(basename      "${CURL_INCLUDES}" HAVE_BASENAME)
 check_symbol_exists(socket        "${CURL_INCLUDES}" HAVE_SOCKET)
 check_symbol_exists(select        "${CURL_INCLUDES}" HAVE_SELECT)