Christopher Smith wrote:
Andrew Lentvorski wrote:
The bug is in handling integers. There are two options for integer
overflow:
1) Die. Period. Do not silently truncate, overflow, saturate, or
whatever.
2) Gracefully degrade. Switch to a slower version of integer which
can handle the greater required precision. eg. Lisp bignums, Python
longs, or Java BigInteger.
You forgot two other options:
3) overflow silently. This is sometimes the exact desired behavior
(which is why it's spec'd to be silent for C, perhaps not a good idea
for the general case, but it really comes in handy when you need it).
The reason why it is spec'd silent for C is that they have no portable
way to signal anything extraordinary.
4) signal the overflow, let the application decide what to do about it.
For example, you'll find lots of code out there which dynamically grows
buffer's by powers of 2. When you get to 2^31 and it's time to grow the
buffer again, the desired behavior is probably to grow the buffer to
something like 2^31 + 2^30, rather than to die or switch to using a
larger integer (particularly if your runtime can't allocate a buffer >
2^32).
I consider this part of "Die.", but okay. Again, the problem is that C
has no mechanism to signal this. C++ exceptions work fine for this, though.
I wish language designers would just finally get it through their
heads that int's should have infinite precision and floating point
numbers should be *decimal* floating point instead of *binary*
floating point.
It would save *so* much time and trouble.
Yeah, and cause so much more trouble elsewhere......
Prove it.
Systems with gracefully degrading ints just don't have
overflow/underflow bugs. The only "problem" is that programs
occasionally slow down because somebody overflowed the range.
Unfortunately, the same experience doesn't exist for decimal floating
point. However, I can tell you that I have yet to meet even a good
programmer who can write binary floating point code that doesn't have
all manner of horrible problems.
-a
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