--- old/src/jdk.incubator.jextract/share/classes/jdk/incubator/jextract/tool/HandleSourceFactory.java	2020-01-27 14:36:52.000000000 +0530
+++ new/src/jdk.incubator.jextract/share/classes/jdk/incubator/jextract/tool/HandleSourceFactory.java	2020-01-27 14:36:52.000000000 +0530
@@ -78,6 +78,24 @@
         this.pkgName = pkgName;
     }
 
+    private static String getCLangConstantsHolder() {
+        String prefix = "jdk.incubator.foreign.MemoryLayouts.";
+        String arch = System.getProperty("os.arch");
+        String os = System.getProperty("os.name");
+        if (arch.equals("amd64") || arch.equals("x86_64")) {
+            if (os.startsWith("Windows")) {
+                return prefix + "WinABI";
+            } else {
+                return prefix + "SysV";
+            }
+        } else if (arch.equals("aarch64")) {
+            return prefix + "AArch64ABI";
+        }
+        throw new UnsupportedOperationException("Unsupported os or arch: " + os + ", " + arch);
+    }
+
+    private static final String C_LANG_CONSTANTS_HOLDER = getCLangConstantsHolder();
+
     public JavaFileObject[] generate(Declaration.Scoped decl) {
         builder.addPackagePrefix(pkgName);
         builder.classBegin(clsName);
@@ -99,7 +117,7 @@
                     fileFromString(pkgName, clsName, src),
                     fileFromString(pkgName,"RuntimeHelper", (pkgName.isEmpty()? "" : "package " + pkgName + ";\n") +
                             Files.readAllLines(Paths.get(runtimeHelper.toURI()))
-                            .stream().collect(Collectors.joining("\n")))
+                            .stream().collect(Collectors.joining("\n")).replace("${C_LANG}", C_LANG_CONSTANTS_HOLDER))
             };
         } catch (IOException ex) {
             throw new UncheckedIOException(ex);
--- old/src/jdk.incubator.jextract/share/classes/jdk/incubator/jextract/tool/resources/RuntimeHelper.template	2020-01-27 14:36:55.000000000 +0530
+++ new/src/jdk.incubator.jextract/share/classes/jdk/incubator/jextract/tool/resources/RuntimeHelper.template	2020-01-27 14:36:54.000000000 +0530
@@ -16,7 +16,7 @@
 import java.util.Arrays;
 import java.util.Optional;
 
-import static jdk.incubator.foreign.MemoryLayouts.*;
+import static ${C_LANG}.*;
 
 public class RuntimeHelper {
 
@@ -195,7 +195,7 @@
             if (c == char.class || c == byte.class || c == short.class || c == int.class || c == long.class) {
                 //it is ok to approximate with a machine word here; numerics arguments in a prototype-less
                 //function call are always rounded up to a register size anyway.
-                return C_LONG;
+                return C_LONGLONG;
             } else if (c == float.class || c == double.class) {
                 return C_DOUBLE;
             } else if (MemoryAddress.class.isAssignableFrom(c)) {