#include <unistd.h>
#include <stdint.h>
#include <limits.h>
#include <stdio.h>

#define JSW_PADDING 2*1024*1024
#define C_Stack_Direction 1
extern void * __libc_stack_end;

#if defined(NO_OPT)
#pragma GCC push_options
#pragma GCC optimize ("O0")
#endif
#if defined(NO_RETURN)
#   define RinitJVM_with_padding_RETURN(RVAL) { RVAL; }
void
#else
#   define RinitJVM_with_padding_RETURN(RVAL) { return RVAL; }
intptr_t
#endif
RinitJVM_with_padding(
    char        *dumdum,
    intptr_t    padding,
    char        *last
)
{
    intptr_t    dp;
    char        dummy[1];
    dummy[0] = (char)(uintptr_t)&dummy;
    padding -= (dp = (last - dummy) * C_Stack_Direction);
#if !defined(NO_PRINTF)
    printf("%p %p: padding = %p ; dp = %p\n", __builtin_frame_address(0), dummy, padding, dp);
#endif
    if ( padding > 0 )
        RinitJVM_with_padding_RETURN( RinitJVM_with_padding(dumdum, padding, dummy) )
    else
        RinitJVM_with_padding_RETURN( (uintptr_t)dummy );
        
}
#if defined(NO_OPT)
#pragma GCC pop_options
#endif


int
main()
{
    char dummy[1], dummy2[45];
    uintptr_t R_CStackStart = (uintptr_t) __libc_stack_end;
    intptr_t R_CStackLimit = 8192 * 1024;

    intptr_t padding = 0;
    {
        int dummy;
        intptr_t usage = (R_CStackStart - (uintptr_t)&dummy);
        usage += JSW_PADDING + 512; /* 512 is a buffer for C recursive calls */
        if(R_CStackLimit == -1 || usage < ((intptr_t) R_CStackLimit))
            padding = JSW_PADDING;
    }

    /* reduce the risk that dummy will be optimized out */
    dummy[0] = (char) (uintptr_t) &dummy;
    printf("padding = %p\n", padding);
#if defined(NO_RETURN)
    RinitJVM_with_padding(dummy, padding, dummy);
#else
    padding = RinitJVM_with_padding(dummy, padding, dummy);
    printf("FINAL:  %p - %p = %p\n", dummy, padding, (intptr_t)dummy - padding);
#endif
    return 0;
}