Static-compatible init of JNA native layer

When operating under static linkage in SVM (Native Image), JNA's
`JNI_OnLoad` hooks are not run. We need to sanity-check at the
first JNI border and run static initialization manually.

Additionally, `JNI_OnLoad` should be provided in static contexts
as `JNI_OnLoad_jnidispatch`. This changeset fixes both issues.

Signed-off-by: Sam Gammon <sam@elide.ventures>
Signed-off-by: Dario Valdespino <dario@elide.ventures>

Author: sgammon

common.xml

@@ -27,7 +27,7 @@
     <property name="jni.revision" value="2"/>
     <property name="jni.build" value="0"/> <!--${build.number}-->
     <property name="jni.version" value="${jni.major}.${jni.minor}.${jni.revision}"/>
-    <property name="jni.md5" value="5fb98531302accd485c534c452dd952a"/>
+    <property name="jni.md5" value="eea709d4f4531903eb04ab51ff3840ce"/>
     <property name="spec.title" value="Java Native Access (JNA)"/>
     <property name="spec.vendor" value="${vendor}"/>
     <property name="spec.version" value="${jna.major}"/>

native/Makefile

@@ -62,6 +62,7 @@ JAVA_INCLUDES=-I"$(JAVA_HOME)/include" \
 BUILD=../build/native
 JAVAH=$(BUILD)
 INSTALLDIR=../build/$(OS)
+JNA_STATIC=no
 JNIDISPATCH_OBJS=$(BUILD)/dispatch.o $(BUILD)/callback.o $(EXTRAOBJS)
 RSRC=$(BUILD)/rsrc.o
 DLLCB=$(BUILD)/dll-callback.o
@@ -342,6 +343,10 @@ ifeq ($(ARCH),ppc)
 endif
 endif
 
+ifeq ($(JNA_STATIC),yes)
+COPT+=-DJNA_STATIC=1
+endif
+
 # CC_OPTS only applied to objects build for jnidispatch, not for libffi
 # -Wno-unknown-warning-option
 #                => Suppress warning for unknown warnings
@@ -497,8 +502,23 @@ $(LIBRARY): $(JNIDISPATCH_OBJS) $(FFI_LIB)
 	$(LD) $(LDFLAGS) $(JNIDISPATCH_OBJS) $(FFI_LIB) $(LIBS)
 	$(STRIP) $@
 
-$(LIBRARY_STATIC): $(JNIDISPATCH_OBJS) $(FFI_LIB)
+static-objs: $(FFI_LIB) $(JNIDISPATCH_OBJS)
+	@# the rebuild enters here
+
+$(LIBRARY_STATIC): $(LIBRARY) $(JNIDISPATCH_OBJS) $(FFI_LIB)
+	@# we force a rebuild of the JNI dispatch objects, but in static mode. this is safe
+	@# because they are cleaned afterward, and `$(LIBRARY)` is guaranteed to have finished
+	@# by now, along with `$(JNIDISPATCH_OBJS)`. we replace the objects again once we are
+	@# finished, to avoid poisoning the shared library on the next build.
+	@#
+	@# this looks like it may be trickery, but it really isn't. see `dispatch.c` for how the
+	@# macro is used; it causes `JNI_OnLoad` to be exported as `JNI_OnLoad_jnidispatch` etc
+	@# instead, so that it can safely be loaded for static JNI.
+	rm -f $(JNIDISPATCH_OBJS)
+	$(MAKE) JNA_STATIC=yes static-objs
 	$(AR) rcs $@ $(JNIDISPATCH_OBJS)
+	rm -f $(JNIDISPATCH_OBJS)
+	$(MAKE) STATIC=no static-objs
 
 $(TESTLIB): $(BUILD)/testlib.o
 	$(LD) $(LDFLAGS) $< $(LIBS)

native/dispatch.c

@@ -3314,6 +3314,20 @@ is_protected() {
   return JNI_FALSE;
 }
 
+jint initializeJnaStatics(JNIEnv *env) {
+  int result = JNI_VERSION_1_4;
+  const char* err;
+  if ((err = JNA_init(env)) != NULL) {
+    fprintf(stderr, "JNA: Problems loading core IDs: %s\n", err);
+    result = 0;
+  }
+  else if ((err = JNA_callback_init(env)) != NULL) {
+    fprintf(stderr, "JNA: Problems loading callback IDs: %s\n", err);
+    result = 0;
+  }
+  return result;
+}
+
 JNIEXPORT jboolean JNICALL
 Java_com_sun_jna_Native_isProtected(JNIEnv *UNUSED(env), jclass UNUSED(classp)) {
   return is_protected();
@@ -3335,6 +3349,10 @@ Java_com_sun_jna_Native_getNativeVersion(JNIEnv *env, jclass UNUSED(classp)) {
 #ifndef JNA_JNI_VERSION
 #define JNA_JNI_VERSION "undefined"
 #endif
+  // sanity check initialization
+  if (classString == NULL) {
+    initializeJnaStatics(env);
+  }
   return newJavaString(env, JNA_JNI_VERSION, CHARSET_UTF8);
 }
 
@@ -3346,39 +3364,50 @@ Java_com_sun_jna_Native_getAPIChecksum(JNIEnv *env, jclass UNUSED(classp)) {
   return newJavaString(env, CHECKSUM, CHARSET_UTF8);
 }
 
-JNIEXPORT jint JNICALL
-JNI_OnLoad(JavaVM *jvm, void *UNUSED(reserved)) {
+JNIEXPORT jboolean JNICALL Java_com_sun_jna_Native_isStaticEnabled(JNIEnv * UNUSED(env), jclass UNUSED(classp)) {
+#ifdef JNA_STATIC
+    return JNI_TRUE;
+#else
+    return JNI_FALSE;
+#endif
+}
+
+JNIEXPORT jint JNICALL Java_com_sun_jna_Native_initializeStatic(JNIEnv *env, jclass UNUSED(classp)) {
+    return initializeJnaStatics(env);
+}
+
+jint setupJna(JavaVM *jvm) {
   JNIEnv* env;
-  int result = JNI_VERSION_1_4;
   int attached = (*jvm)->GetEnv(jvm, (void *)&env, JNI_VERSION_1_4) == JNI_OK;
-  const char* err;
-
   if (!attached) {
     if ((*jvm)->AttachCurrentThread(jvm, (void *)&env, NULL) != JNI_OK) {
       fprintf(stderr, "JNA: Can't attach native thread to VM on load\n");
       return 0;
     }
   }
-
-  if ((err = JNA_init(env)) != NULL) {
-    fprintf(stderr, "JNA: Problems loading core IDs: %s\n", err);
-    result = 0;
-  }
-  else if ((err = JNA_callback_init(env)) != NULL) {
-    fprintf(stderr, "JNA: Problems loading callback IDs: %s\n", err);
-    result = 0;
-  }
+  int result = initializeJnaStatics(env);
   if (!attached) {
     if ((*jvm)->DetachCurrentThread(jvm) != 0) {
       fprintf(stderr, "JNA: could not detach thread on initial load\n");
     }
   }
-
   return result;
 }
 
-JNIEXPORT void JNICALL
-JNI_OnUnload(JavaVM *vm, void *UNUSED(reserved)) {
+#ifdef JNA_STATIC
+JNIEXPORT jint JNICALL
+JNI_OnLoad_jnidispatch(JavaVM *jvm, void *UNUSED(reserved)) {
+  setupJna(jvm);
+  return JNI_VERSION_1_8;  // upgrade to JNI_VERSION_1_8; required for static JNI
+}
+#else
+JNIEXPORT jint JNICALL
+JNI_OnLoad(JavaVM *jvm, void *UNUSED(reserved)) {
+  return setupJna(jvm);
+}
+#endif
+
+void unloadJna(JavaVM *vm) {
   jobject* refs[] = {
     &classObject, &classClass, &classMethod,
     &classString,
@@ -3443,6 +3472,16 @@ JNI_OnUnload(JavaVM *vm, void *UNUSED(reserved)) {
   }
 }
 
+#ifdef JNA_STATIC
+JNIEXPORT void JNICALL JNI_OnUnload_jnidispatch(JavaVM *jvm, void *UNUSED(reserved)) {
+  unloadJna(jvm);
+}
+#else
+JNIEXPORT void JNICALL JNI_OnUnload(JavaVM *jvm, void *UNUSED(reserved)) {
+  unloadJna(jvm);
+}
+#endif
+
 JNIEXPORT void JNICALL
 Java_com_sun_jna_Native_unregister(JNIEnv *env, jclass UNUSED(ncls), jclass cls, jlongArray handles) {
   jlong* data = (*env)->GetLongArrayElements(env, handles, NULL);

src/com/sun/jna/Native.java

@@ -33,6 +33,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.UnsupportedEncodingException;
+import java.lang.System;
 import java.lang.ref.Reference;
 import java.lang.ref.WeakReference;
 import java.lang.reflect.Array;
@@ -947,6 +948,20 @@ private static void loadNativeDispatchLibrary() {
         }
 
         String libName = System.getProperty("jna.boot.library.name", "jnidispatch");
+
+        // if in static init mode, load the library by name and force-run the initializer
+        if (!Boolean.getBoolean("jna.skipStatic")) {
+            try {
+                System.loadLibrary(libName);
+                if (isStaticEnabled()) {
+                    int jniApiVersion = initializeStatic();
+                    assert jniApiVersion == 0x00010008;  // `JNI_VERSION_1_8`
+                }
+                return;
+            } catch (UnsatisfiedLinkError err) {
+                // continue
+            }
+        }
         String bootPath = System.getProperty("jna.boot.library.path");
         if (bootPath != null) {
             // String.split not available in 1.4
@@ -1198,6 +1213,8 @@ else if (!Boolean.getBoolean("jna.nounpack")) {
      **/
     private static native int sizeof(int type);
 
+    private static synchronized native boolean isStaticEnabled();
+    private static synchronized native int initializeStatic();
     private static native String getNativeVersion();
     private static native String getAPIChecksum();
 
@@ -2020,6 +2037,7 @@ public static void main(String[] args) {
             ? pkg.getImplementationVersion() : DEFAULT_BUILD;
         if (version == null) version = DEFAULT_BUILD;
         System.out.println("Version: " + version);
+        System.out.println(" Static: " + isStaticEnabled());
         System.out.println(" Native: " + getNativeVersion() + " ("
                            + getAPIChecksum() + ")");
         System.out.println(" Prefix: " + Platform.RESOURCE_PREFIX);