java memory allcation with gcj

java memory allcation with gcj

[isuru herath]

Dear All,

I am interested in studying how "new" allocates memory when running as native binary. For this I wrote a simple Java class which just create an int array. Then I generate the assembly with gcj -S option. There I spotted the call to _Jv_NewPrimArray. Since the result of the call is stored in eax register I check the value of the eax register after this call. But it is giving a small number. I tried the same thing with C. There I spotted the call to malloc and check the eax after the malloc call and it has the same value as the &variable_name has.

So my objective is to identify the are of memory allocated by "new". Any help/advice on this regard is greatly appreciated.

thanks and regards,
Isuru


      

Re: java memory allocation with gcj

[Andrew Haley]

isuru herath wrote:

 > I am interested in studying how "new" allocates memory when running
 > as native binary. For this I wrote a simple Java class which just
 > create an int array. Then I generate the assembly with gcj -S
 > option. There I spotted the call to _Jv_NewPrimArray. Since the
 > result of the call is stored in eax register I check the value of
 > the eax register after this call. But it is giving a small number. I
 > tried the same thing with C. There I spotted the call to malloc and
 > check the eax after the malloc call and it has the same value as the
 > &variable_name has.

_Jv_NewPrimArray calls the memory allocator (actually part of the
Boehm garbage collector) which calls
mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, ..) to map
the memory.

Andrew.