Re: detecting arithmetic overflows - Compiler specific flags

[Paul Pluzhnikov]

Karthik Kumar <kaykaydreamz_nospamplz@yahoo.com> writes:

>     I am writing this application that needs a lot of arithmetic
> calculations. I was wondering if the GNU C++ compiler specifies any
> way of detecting arithmetic overflows. ( some extensions or flags or
> some options).

"The C++ Programming Language", 3rd edition, p.122:

Implementations do not have to check for arithmetic overflow and
hardly any do.

>     I was looking at overflow_error class provided by stdexcept
>     library in C++. That does not seem to be raised automatically.

Same book, p. 385, lists 'overflow_error' as being thrown *only*
from bitset<>::to_ulong().

> How would I handle similar situations ?

You'll have to handle them yourself, e.g.

  inline short mult(short a, short b) {
      int res = a * b;
      if (SHRT_MIN <= res && res <= SHRT_MAX) return res;
      throw overflow_error();
  }        
...

         short a = -10000;
         short b = mult(a, 8); // now throws

Cheers,
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