I have not done any serious JNI work in about 20+ years and it was on another
platform (OS/2) rather than z/OS. But I've inherited some code and I noticed
something that I don't think is right, but would like to get a confirmation
from anyone with more experience. This is a code fragment as written.
/* --- Get the parm input, and convert to EBCDIC ---- */
const char* msg=(*env)->GetStringUTFChars(env,jParm,0);
/*
** Convert string to EBCDIC
*/
__atoe((char*) msg);
/*
** Release the passed string
*/
(*env)->ReleaseStringUTFChars(env, jParm, msg);
/* --- Setup 1K Area to pass (leave space for NULL) */
passarea = malloc(1024); /* Get area */
memset(passarea, 0, 1024); /* Clear area */
strcpy(passarea,msg); /* Put parm in */
Based on what I've read about the GetStringxxxx and ReleaseStringxxx I believe
that the ReleaseStringxxx should be placed AFTER the strcpy of the msg into the
passarea. The documentation says to call the ReleastString once you are done
using the string.
That leads me to believe that the code fragment should look like the following.
/* --- Get the parm input, and convert to EBCDIC ---- */
const char* msg=(*env)->GetStringUTFChars(env,jParm,0);
/*
** Convert string to EBCDIC
*/
__atoe((char*) msg);
/* --- Setup 1K Area to pass (leave space for NULL) */
passarea = malloc(1024); /* Get area */
memset(passarea, 0, 1024); /* Clear area */
strcpy(passarea,msg); /* Put parm in */
/*
** Release the passed string
*/
(*env)->ReleaseStringUTFChars(env, jParm, msg);
I'm really surprised that this code does not abend or toss some kind of error,
if the string is getting marked as released before we are done with it. I
suppose it could be related to when the JVM actually runs the garbage
collection that recovers the storage, but to my mind this is an error just
waiting to happen.
Am I right? If not can someone provide clarification as to why the original
form is correct?
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