Bug 161944 – stringProtoFuncRepeatCharacter will return `null` when it should not

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Saam Barati]

It doesn't properly detect when an int is in double form.
However, there is also a deeper problem, where it looks like numbers are being polluted into double form instead
of staying in integer form, even though there is only one comparison on that number that needs it in double form.
I'm looking at String.prototype.padStart. the @toLength builtin will cause the pollution.

See this example:
```

function logLinesWithContext(n, context) {
    let start = n - context;
    let end = n + context;
    for (let x = start; x <= end; ++x) {
        let number = x.toString().padStart(3);
        // WHAT?!
        if (parseInt(number) != x)
            print(number);
    }
}

let numbers = [
    19,19,19,19,19,19,19,20,20,20,20,20,20,20,11,11,11,11,11,11,11,20,20,20,20,
    20,20,20,15,15,15,15,15,15,15,21,21,21,21,21,21,21,19,19,19,19,19,19,19,20,
    20,20,20,20,20,20,20,20,20,20,20,20,20,21,21,21,21,21,21,21,24,24,24,24,24,
    24,24,25,25,25,25,25,25,25,11,11,11,11,11,11,11,25,25,25,25,25,25,25,15,15,
    15,15,15,15,15,25,25,25,25,25,25,25,7,7,7,7,7,7,7,26,26,26,26,26,26,26,24,
    24,24,24,24,24,24,25,25,25,25,25,25,25,11,11,11,11,11,11,11,25,25,25,25,25,
    25,25,26,26,26,26,26,26,26,24,24,24,24,24,24,24,25,25,25,25,25,25,25,11,11,
    11,11,11,11,11,12,12,12,12,12,12,12,25,25,25,25,25,25,25,15,15,15,15,15,15,
    15,16,16,16,16,16,16,16,25,25,25,25,25,25,25,7,7,7,7,7,7,7,8,8,8,8,8,8,8,
    26,26,26,26,26,26,26,24,24,24,24,24,24,24,25,25,25,25,25,25,25,11,11,11,11,
    11,11,11,12,12,12,12,12,12,12,25,25,25,25,25,25,25,15,15,15,15,15,15,15,16,
    16,16,16,16,16,16,25,25,25,25,25,25,25,7,7,7,7,7,7,7,8,8,8,8,8,8,8,26,26,
    26,26,26,26,26,29,29,29,29,29,29,29,30,30,30,30,30,30,30,35,35,35,35,35,35,
    35,29,29,29,29,29,29,29,30,30,30,30,30,30,30,11,11,11,11,11,11,11,33,33,33,
    33,33,33,33,35,35,35,35,35,35,35,39,39,39,39,39,39,39,40,40,40,40,40,40,40,
    11,11,11,11,11,11,11,40,40,40,40,40,40,40,40,40,40,40,40,40,40,15,15,15,15,
    15,15,15,41,41,41,41,41,41,41,39,39,39,39,39,39,39,40,40,40,40,40,40,40,40,
    40,40,40,40,40,40,40,40,40,40,40,40,40,41,41,41,41,41,41,41,45,45,45,45,45,
    45,45,46,46,46,46,46,46,46,11,11,11,11,11,11,11,46,46,46,46,46,46,46,15,15,
];
for (let n of numbers)
    logLinesWithContext(n, 3);
```
It will start printing things because the result string is not an integer.

[Saam Barati]

The bug also goes away when @toLength is not inlined into padStart.

[Saam Barati]

Created attachment 290133 [details]
patch

[Yusuke Suzuki]

Comment on attachment 290133 [details]
patch

r=me

[Saam Barati]

Created attachment 290145 [details]
patch

take 2. I removed the caller that expected the null result value and instead made protoFuncRepeatCharacter throw OOM when it will construct too long of a string.

[Yusuke Suzuki]

Comment on attachment 290145 [details]
patch

r=me

[WebKit Commit Bot]

Comment on attachment 290145 [details]
patch

Clearing flags on attachment: 290145

Committed r206573: <http://trac.webkit.org/changeset/206573>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.