Harden NumberToSize against overflows.

Harden NumberToSize against overflows.

The callers to NumberToSize are supposed to validate the number, but
this adds a last line of defense.

R=jkummerow@chromium.org, ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=17733

[Dmitry Lomov (no reviews), 2013-11-14 10:08:50]

PTAL.

[Jakob Kummerow, 2013-11-14 10:17:47]

LGTM.

https://codereview.chromium.org/72323003/diff/1/src/v8conversions.h
File src/v8conversions.h (right):

https://codereview.chromium.org/72323003/diff/1/src/v8conversions.h#newcode64
src/v8conversions.h:64: CHECK(value >= 0
Not that it makes a big difference, but it's sufficient to:

CHECK(value >= 0);
ASSERT(static_cast<unsigned>(value) <= std::numeric_limits<size_t>::max());

or even:

STATIC_ASSERT(Smi::kMaxValue <= std::numeric_limits<size_t>::max());

if that numeric_limits call is static assert capable.

https://codereview.chromium.org/72323003/diff/1/src/v8conversions.h#newcode71
src/v8conversions.h:71: value <= std::numeric_limits<size_t>::max());
nit: I'd align "value" with "value".

[Dmitry Lomov (no reviews), 2013-11-14 10:22:57]

https://codereview.chromium.org/72323003/diff/1/src/v8conversions.h
File src/v8conversions.h (right):

https://codereview.chromium.org/72323003/diff/1/src/v8conversions.h#newcode64
src/v8conversions.h:64: CHECK(value >= 0
On 2013/11/14 10:17:48, Jakob wrote:
> Not that it makes a big difference, but it's sufficient to:
> 
> CHECK(value >= 0);
> ASSERT(static_cast<unsigned>(value) <= std::numeric_limits<size_t>::max());
> 
> or even:
> 
> STATIC_ASSERT(Smi::kMaxValue <= std::numeric_limits<size_t>::max());
> 
> if that numeric_limits call is static assert capable.
Great suggestion, this is by far the commonest case so shaving a couple cycles
here is useful.

[Dmitry Lomov (no reviews), 2013-11-14 11:14:12]

Committed patchset #2 manually as r17733 (presubmit successful).

[Dmitry Lomov (no reviews), 2013-11-14 11:41:37]

On 2013/11/14 11:14:12, Dmitry Lomov (chromium) wrote:
> Committed patchset #2 manually as r17733 (presubmit successful).

Landed for real in r17737.