enable checks for integer overflow/underflow in debug mode

[cristian-ilies-vasile]

See #4014

[dumblob]

There are many algorithms (typically those oriented on performance or low-level coding) relying on overflow/underflow (e.g. embedded development, security algorithms, hash/... algorithms, numerical computation algorithms, etc.).

So I'm afraid checking overflow/underflow would require dedicated syntax for (dis)allowing such checks.

[spytheman]

If you do:

$if !no_overflow_checks ? { 
  // do slower checks here
}

... then when you compile with v -d no_overflow_checks , the checks will be skipped at compile time.

Of course it can do the opposite too:

$if overflow_checks ? {
  // do slower checks
}

... so you can then opt in for slower but potentially safer code by passing -d overflow_checks during compilation.

I am not sure what approach is best for these.

[cristian-ilies-vasile]

My school of thinking was to go down the same route, more or less as for array's index checks.

I mean, let's the compiler add or not based on a command line flag (--enforce_overflow_check) if this type of verification will be injected in C code at compile time.
If the coder use V to animate sprites on a virtual world, then maybe is no need for such strict type of safety.

However for real life applications the developer will engage --enforce_overflow_check and automatically C code will be added to C source code by the V compiler.