[llvm] r271380 - Fix off-by-one error in max integer functions

[John Regehr via llvm-commits]

I'm not sure in what circumstances these functions are used.  It is 
often very bad manners to throw assertions from library code.  But if 
you are writing the code that calls this code, then an assertion 
definitely sounds appropriate.

Probably best to return the correct result for N==64 and then (if 
appropriate) error out for N<1 and N>64.

John


On 6/2/16 12:32 PM, Dylan McKay wrote:
> How do you think this should be handled? Assertion error?
>
> On Thu, Jun 2, 2016 at 10:10 PM, John Regehr <regehr at cs.utah.edu
> <mailto:regehr at cs.utah.edu>> wrote:
>
>          /// Gets the maximum value for a N-bit unsigned integer.
>         -inline uint64_t maxUIntN(uint64_t N) { return UINT64_C(1) << N; }
>         +inline uint64_t maxUIntN(uint64_t N) { return (UINT64_C(1) <<
>         N) - 1; }
>
>
>     This is still wrong unless N is guaranteed to be no greater than 63.
>
>     John
>
>