Fix segmentation fault when calling Zstd.loadDictDecompress(...)

Author: garydgregory

src/main/native/jni_zstd.c

@@ -237,6 +237,7 @@ JNIEXPORT jlong JNICALL Java_com_github_luben_zstd_Zstd_getErrorCode
  */
 JNIEXPORT jint JNICALL Java_com_github_luben_zstd_Zstd_loadDictDecompress
   (JNIEnv *env, jclass obj, jlong stream, jbyteArray dict, jint dict_size) {
+    if (dict == NULL) return -ZSTD_error_dictionary_wrong;
     size_t size = -ZSTD_error_memory_allocation;
     void *dict_buff = (*env)->GetPrimitiveArrayCritical(env, dict, NULL);
     if (dict_buff == NULL) goto E1;

src/test/scala/Zstd.scala

@@ -937,6 +937,13 @@ class ZstdSpec extends AnyFlatSpec with ScalaCheckPropertyChecks {
     assert(Zstd.loadFastDictDecompress(0, null.asInstanceOf[ZstdDictDecompress]) == -32)
   }
 
+  "Zstd" should s"do not cause a segmentation fault in loadDictDecompress()" in {
+    // Avoid:
+    //  0 0x000000010185e7c8 AccessInternal::PostRuntimeDispatch<G1BarrierSet::AccessBarrier<548964ull, G1BarrierSet>, (AccessInternal::BarrierType)2, 548964ull>::oop_access_barrier(void*) + 8 in libjvm.dylib
+    // 1 0x0000000101c17ca8 jni_GetPrimitiveArrayCritical + 340 in libjvm.dylib
+    assert(Zstd.loadDictDecompress(0, null , 0) == -32)
+  }
+
   "ZstdDirectBufferCompressingStream" should s"do nothing on double close but throw on writing on closed stream" in {
     val os  = ByteBuffer.allocateDirect(100)
     val zos = new ZstdDirectBufferCompressingStream(os, 1)