Should you call ReleaseStringUTFChars if GetStringUTFChars returned a copy?

Question

The book "Essential JNI: Java Native Interface" by Rob Gordon contains the following code example to convert a jstring to a C string:

const char* utf_string; jboolean isCopy; utf_string = env->GetStringUTFChars(str, &isCopy); /* ... use string ... */ if (isCopy == JNI_TRUE) {     env->ReleaseStringUTFChars(str, utf_string); } 

Note that it only calls ReleaseStringUTFChars if isCopy is true.

But the book Java Native Interface: Programmer's Guide and Specification (alternate link: http://192.9.162.55/docs/books/jni/html/objtypes.html#5161) says:

The ReleaseString-Chars call is necessary whether GetStringChars has set *isCopy to JNI_TRUE or JNI_FALSE. ReleaseStringChars either frees the copy or unpins the instance, depending upon whether GetStringChars has returned a copy or not.

I am correct in assuming this is a bug in Gordon's book?

Answer 1

Yes, your assumption is correct (you should always call ReleaseStringUTFChars).