As a little learning exercise for D I’m writing a fixed point
library. Part of this is checking standard integer operations for
overflows.
This is the code for adding 2 longs:
int64 add64ov(int64 a, int64 b) {
int64 res;
asm {
mov EAX,a ;
mov EDX,a+4 ;
add EAX,b ;
adc EDX,b+4 ;
jo overflow ;
mov res,EAX ; // Not optimal: cannot do a ret here because of
stack frame previously not correctly set
mov res+4,EDX;
}
return res;
overflow:
throw new OverflowException("Overflow in 64 bit addition");
}
The detour via the res variable is costly; the standard epilogue
(I probably need a frame pointer for the exception throw to work):
mov ESP, EBP
pop EBP
ret
creates an access violation.
Ideas, anyone?
