RFR: 8211163: UNIX version of Java_java_io_Console_echo does not return a clean boolean

Andrew Haley aph at redhat.com
Fri Sep 28 14:13:25 UTC 2018

On 09/28/2018 02:55 PM, Volker Simonis wrote:
> I agree that the native code should be fixed and I think your patch is correct.
> Nevertheless I'd vote for changing it to something like:
> old = (tio.c_lflag & ECHO) == 0 ? JNI_FALSE : JNI_TRUE;
> It's slightly more verbose, but it makes it more obvious that a JNI
> function returning a jboolean should only ever return JNI_FALSE or
> JNI_TRUE. This isn't obvious from your fix - especially not for C
> programmers who produce such code.

Where is the evidence that a function returning a jboolean should only
ever return JNI_FALSE or JNI_TRUE? It doesn't say so in the JNI spec,
only that these values are provided for convenience. They are defined
to be 0 and 1, like so:

#define JNI_FALSE  0
#define JNI_TRUE   1

which are *exactly* the same values that the C != operation
returns. Therefore there is no advantage either in correctness or
clarity gained by using


It's not even pedantically correct, merely verbose.

> Also, it would be good to change the bug summary to something more
> generic like "Fix native library code which does not return a clean
> boolean" and fix the additional occurrences of this antipattern
> reported by Matthias in this mail thread:
> http://mail.openjdk.java.net/pipermail/jdk-dev/2018-September/thread.html#1986
> I think it would makelittle sense to open a new issue for each of
> them.


Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671

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