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).