Increase maximum supported fixed args on varargs calls from 3 to 255

Author: andrew-nowak

CHANGES.md

@@ -11,6 +11,12 @@ Features
 Bug Fixes
 ---------
 * [#1501](https://github.com/java-native-access/jna/pull/1501): `Library.OPTION_STRING_ENCODING` is ignore for string arguments function calls - [@matthiasblaesing](https://github.com/matthiasblaesing).
+* [#1504](https://github.com/java-native-access/jna/pull/1504): Increase maximum supported fixed args on varargs calls from 3 to 255 - [@andrew-nowak](https://github.com/andrew-nowak).
+
+Important Changes
+-----------------
+* The interfaces between Java and native code have changed, so `libjnidispatch`
+  must be rebuilt to be compatible with this release.
 
 Release (5.13.0)
 ================

native/dispatch.c

@@ -144,9 +144,10 @@ extern "C" {
   PSTART(); memset(D,C,L); PEND(ENV); \
 } while(0)
 
-#define MASK_CC          com_sun_jna_Function_MASK_CC
-#define THROW_LAST_ERROR com_sun_jna_Function_THROW_LAST_ERROR
-#define USE_VARARGS      com_sun_jna_Function_USE_VARARGS
+#define MASK_CC           com_sun_jna_Function_MASK_CC
+#define THROW_LAST_ERROR  com_sun_jna_Function_THROW_LAST_ERROR
+#define USE_VARARGS       com_sun_jna_Function_USE_VARARGS
+#define USE_VARARGS_SHIFT com_sun_jna_Function_USE_VARARGS_SHIFT
 
 /* Cached class, field and method IDs */
 static jclass classObject;
@@ -480,7 +481,7 @@ dispatch(JNIEnv *env, void* func, jint flags, jobjectArray args,
   callconv_t callconv = flags & MASK_CC;
   const char* volatile throw_type = NULL;
   const char* volatile throw_msg = NULL;
-  int fixed_args = (flags & USE_VARARGS) >> 7;
+  int fixed_args = (flags >> USE_VARARGS_SHIFT) & USE_VARARGS;
 
   nargs = (*env)->GetArrayLength(env, args);
 

native/testlib.c

@@ -908,6 +908,19 @@ addVarArgs(const char *fmt, ...) {
   return sum;
 }
 
+EXPORT int32_t
+addSeveralFixedArgsAndVarArgs(int a, int b, int c, int d, int n_varargs, ...) {
+  va_list ap;
+  int32_t sum = a + b + c + d;
+  va_start(ap, n_varargs);
+
+  for (int i = 0; i < n_varargs; i++) {
+    sum += va_arg(ap, int32_t);
+  }
+  va_end(ap);
+  return sum;
+}
+
 EXPORT void
 modifyStructureVarArgs(const char* fmt, ...) {
   struct _ss {

src/com/sun/jna/Function.java

@@ -76,9 +76,12 @@ public interface PostCallRead {
     /** Whether to throw an exception if last error is non-zero after call. */
     @java.lang.annotation.Native
     public static final int THROW_LAST_ERROR = 0x40;
-    /** Mask for number of fixed args (1-3) for varargs calls. */
+    /** Mask for number of fixed args (max 255) for varargs calls. */
     @java.lang.annotation.Native
-    public static final int USE_VARARGS = 0x180;
+    public static final int USE_VARARGS = 0xFF;
+    /** Offset of USE_VARARGS in call flags */
+    @java.lang.annotation.Native
+    public static final int USE_VARARGS_SHIFT = 7;
 
     static final Integer INTEGER_TRUE = Integer.valueOf(-1);
     static final Integer INTEGER_FALSE = Integer.valueOf(0);
@@ -410,7 +413,7 @@ Object invoke(Object[] args, Class<?> returnType, boolean allowObjects) {
     /* @see NativeLibrary#NativeLibrary(String,String,long,Map) implementation */
     Object invoke(Object[] args, Class<?> returnType, boolean allowObjects, int fixedArgs) {
         Object result = null;
-        int callFlags = this.callFlags | ((fixedArgs & 0x3) << 7);
+        int callFlags = this.callFlags | ((fixedArgs & USE_VARARGS) << USE_VARARGS_SHIFT);
         if (returnType == null || returnType==void.class || returnType==Void.class) {
             Native.invokeVoid(this, this.peer, callFlags, args);
             result = null;

test/com/sun/jna/VarArgsTest.java

@@ -41,6 +41,7 @@ protected List<String> getFieldOrder() {
             }
         }
         public int addVarArgs(String fmt, Number... args);
+        public int addSeveralFixedArgsAndVarArgs(int a, int b, int c, int d, int nArgs, Integer... args);
         public String returnStringVarArgs(String fmt, Object... args);
         public void modifyStructureVarArgs(String fmt, Object... args);
         public String returnStringVarArgs2(String fmt, String... args);
@@ -102,6 +103,22 @@ public void testStringVarArgsFull() {
                      lib.returnStringVarArgs2("", "Test"));
     }
 
+    public void testSeveralFixedAndVarArgs() {
+        int fixedarg1 = 1;
+        int fixedarg2 = 2;
+        int fixedarg3 = 3;
+        int fixedarg4 = 4;
+        int vararg1 = 100;
+        int vararg2 = 200;
+
+        int expected = fixedarg1 + fixedarg2 + fixedarg3 + fixedarg4 + vararg1 + vararg2;
+        int result = lib.addSeveralFixedArgsAndVarArgs(fixedarg1, fixedarg2, fixedarg3, fixedarg4,
+                                                       2, vararg1, vararg2);
+
+        assertEquals("varargs not passed correctly with multiple fixed args",
+                     expected, result);
+    }
+
     public void testAppendNullToVarargs() {
         Number[] args = new Number[] { Integer.valueOf(1) };
         assertEquals("No trailing NULL was appended to varargs list",