Use _WIN32 to detect if building for Windows.

build.gradle

@@ -130,7 +130,6 @@ libraries {
             } else if (targetPlatform.operatingSystem.windows) {
                 cppCompiler.args "-I${org.gradle.internal.jvm.Jvm.current().javaHome}/include"
                 cppCompiler.args "-I${org.gradle.internal.jvm.Jvm.current().javaHome}/include/win32"
-                cppCompiler.define("WIN32")
                 linker.args "Shlwapi.lib", "Advapi32.lib"
             } else if (targetPlatform.operatingSystem.freeBSD) {
                 cppCompiler.args '-I', "${org.gradle.internal.jvm.Jvm.current().javaHome}/include"

src/curses/cpp/curses.cpp

@@ -17,7 +17,7 @@
 /*
  * Curses functions
  */
-#ifndef WIN32
+#ifndef _WIN32
 
 #include "native.h"
 #include "generic.h"

src/main/cpp/posix.cpp

@@ -17,7 +17,7 @@
 /*
  * POSIX platform functions.
  */
-#ifndef WIN32
+#ifndef _WIN32
 
 #include "native.h"
 #include "generic.h"

src/main/cpp/win.cpp

@@ -14,7 +14,7 @@
  *    limitations under the License.
  */
 
-#ifdef WIN32
+#ifdef _WIN32
 
 #include "native.h"
 #include "generic.h"

src/shared/cpp/generic_posix.cpp

@@ -17,7 +17,7 @@
 /*
  * POSIX platform functions.
  */
-#ifndef WIN32
+#ifndef _WIN32
 
 #include "native.h"
 #include "generic.h"