Re: JNI on ARM/XScale

[Andrew Haley <aph at redhat dot com>]

Jari Korva writes:
 > On Thu, 30 Sep 2004, Bryce McKinlay wrote:
 > > Hmm, so if you printf() lib_name immediately before and after the
 > > JvSynchronize(), it prints the correct value before the call and
 > > corrupted afterwards? If so, that sounds like a C++ compiler bug, as a
 > > value on the stack is somehow being overwritten.
 > >
 > > You could try building natRuntime.cc with -O0 to confirm this theory.
 > 
 > Thanks again! I removed -O2 from libjava/Makefile, touched natRuntime.cc
 > and ran make again. Then I rebuild my JNI-HelloWorld - and it really
 > worked!
 > 
 > I also tried printfs instead of debugger on -O2 optimized binary. That
 > way, it seems that the value is corrupted already before JvSynchronize.
 > The trace and modified source are below (the most bizarre thing is that it
 > jumps directly from trace 3-1 to 4).

There's nothing weird about that: all it means is that you're getting
an ArrayIndexOutOfBoundsException.  This is Bad.

 > 
 > ...
 > JKO DEBUG 3-1: libhello
 > JKO DEBUG 3-2: libhello
 > JKO DEBUG 3-3: libhello
 > JKO DEBUG 3-1: libhello
 > JKO DEBUG 4:
 > ...
 > 
 >       try
 >         {
 >           for (int i = 0; i < 10; ++i)
 >             {
 > printf("JKO DEBUG 3-1: %s\n", lib_name);

You need to do fflush() after every printf, or setvbuf (NULL).

Andrew.