Bug 166475 – WebAssembly: parseVarUInt1 should take a uint32_t not a uint8_t

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: JavaScriptCore

[Saam Barati]

We're loosing the top 3 bytes here, and that's bad. We loose them because we do static_cast<uint32_t>(uint8_t).
This is bad if say I parseVarUint1 and expect the result to be zero.
Right now, if somebody passed in:
0xffffff00
We'd think it's zero because of how we drop the top 3 bytes. That's clearly wrong.

[Radar WebKit Bug Importer]

<rdar://problem/29803564>

[Saam Barati]

The bug is actually here:

```
232 template<typename SuccessType>
233 ALWAYS_INLINE bool Parser<SuccessType>::parseVarUInt1(uint8_t& result)
234 {
235     uint32_t temp;
236     if (!parseVarUInt32(temp))
237         return false;
238     result = static_cast<uint8_t>(temp);
239     return temp <= 1;
240 } 
```

We should check the value before the cast!
I'll just fix this as part of:
https://bugs.webkit.org/show_bug.cgi?id=166448

[Saam Barati]

*** This bug has been marked as a duplicate of bug 166448 ***