[Python-Dev] Memory size overflows

[Guido van Rossum]

I think this discussion is suffering from the desire to
over-generalize.

Armin, can you show us how to multiply two nonnegative ints together
with an overflow "block" as Tim suggested earlier?  I.e. a macro
callable as

  SAFE_MULTIPLY(destination, src1, src2, on_overflow);

meaning roughly

  destination = src1 * src2;
  if (<overflow detected>)
     on_overflow;

I currently use something like this as the overflow test in a few places:

  if (src1 && destination / src1 != src2)

but as Tim points out the division can kill us unless src1 is a
constant...  How would you spell this without doing a division?

--Guido van Rossum (home page: http://www.python.org/~guido/)