Dynamic arrays allocation size

[bearophile]

Steven Schveighoffer:

> If we treated it as an error, then it would be very costly to 
> implement, every operation would have to check for overflow.

I have used similar tests and it's not very costly, not 
significantly more costly than array bound tests.

In the meantime Clang has introduced similar run-time tests for 
C/C++ code. So C/C++ are now better (more modern, safer) than the 
D language/official compiler in this regard.

(And Issue 4835 is about compile-time constants. CFFE is already 
plenty slow, mostly because of memory allocations. Detecting 
overflow in constants is not going to significantly slow down 
compilation, and it has no effect on the runtime. Even GCC 4.3.4 
performs such compile-time tests.)


> The CPU does not assist in this.

The X86 CPUs have overflow and carry flags that help.

Bye,
bearophile