On Wed, 16 Aug 2023 12:33:47 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
>> When we read the 64 bit values in the code, the values are 64 bits though.
>> So static_cast<> to narrow the result is more correct ?
>
> This code:
>
> uint64_t isa;
> if (!_reader.read_uleb128(&isa, 4)) {
> // isa register is 4 bytes wide.
> return false;
> }
> _state->_isa = isa; // only save 4 bytes
>
> returns 64 bit of information into isa from this read_uleb128 call, even
> though it passes 4.
I've quickly skimmed through the usages of `read_uleb128`. We only seem to be
reading either directly into a proper `uint64_t` or we are reading 4 bytes
(i.e. `check_size = 4`). In the latter case, we could either:
- add a `static_cast` for the read value when storing it into a 32 bit field,
as for example for `isa` above (i.e. `_state->_isa =
static_cast<uint32_t>(isa)`).
- provide a 32 bit `read_uleb128()` version that hides the casting.
I guess it's fine to just go with a `static_cast` when storing to a field for
the few cases we have.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/15233#discussion_r1295863147
