java memory allocation with gcj

Fri Nov 6 09:54:00 GMT 2009

isuru herath wrote:
 > Thanks for the reply. I tried in x $eax gdb after the new being executed an
 > it was giving me the following.
 > 0x804a0e0 <_ZN13test_java_new6class$E>: 0xb7a4afe8
 >
 > When converted to decimal it was 134521056 which seems close to that of C.
 > Could you please tell me what the other value represents here.
 >
 > Seems like the way I was doing is wrong. But I couldn't find another way.
 >
 > This is my Java class.
 >
 > class test_java_new
 > {
 > public static void main(String[]args)
 > {
 > int isuru[]=new int[2];
 > isuru[0] = 12345;
 > }
 > }
 >
 > Then I compiled this with gcj -S. Then I open the test_java_new.s file.
 > There I add following lines after the
 > call _Jv_NewPrimArray line.
 >
 > The lines I am adding are
 > pushl %ecx #;for start location
 > movl %eax, %ecx #;copy value in eax to ecx
 > push %eax #;the memory tag
 > movl 5,ドル %eax #;set eax to HEAP tag
 > xchg %bx, %bx #;magic instruction
 > popl %eax
 > popl %ecx
This looks right.
 > Why I am doing this is, when the xchg %bx, %bx is executed my
 > simulator (Simics) triggers an event and my hardware module can get
 > the control of the system. So that I can pass information from the
 > user program to my hardware module. But when I check the eax
 > register at my hardware module after xchg %bx, %bx , I got that
 > small number which is 166816. But when I add the same assembly code
 > soon after the call malloc in a gcc generated assembly of a C
 > program, my hardware module gets the correct address. Therefore I
 > was thinking it should be the same here.
It certainly should be. We know that when you print out $eax in gdb,
you get the correct value.
 > Some other thing I noticed is that when I invoke x $eax after the
 > isuru[0] = 12345; I got 0X28bc0 which is quite similar to 166848. I
 > don't know this helps you to help me to clarify my problem.
Let's see the assembly code of the whole function, before and after
your changes.
Andrew.