Status: New
Owner: ----
New issue 3692 by [email protected]: function suddenly becomes undefined
https://code.google.com/p/v8/issues/detail?id=3692
This test shows what we believe is v8 generating invalid optimized code,
causing a function to suddenly become undefined. This appears to affect
when.js versions 3.4.2 and higher, although the failure appears to happen
under different conditions depending on the version of when.js and/or the
version of v8 (via Node.js).
Here's an executable showing the problem, and a more complete description
of the issue, expected and actual results, etc.:
https://github.com/briancavalier/when-v8-invalid-optimization
### Environment
The test in the repo above is design to show the failure on:
* Node 0.10.33
* when.js 3.6.0
### Expected result
Program completes without error.
### Actual result
Program fails at a seemingly random, but reproducible iteration.
The stack trace below points to this line in the `_beget` function:
https://github.com/cujojs/when/blob/3.6.0/lib/makePromise.js#L166).
```
<lots more output above>
#57 reading file with promise: `dist/lodash.compat.js`
#57 parsing file: `dist/lodash.compat.js`
**
* @license
* Lo-Dash 2.4.1 (Custom Build) <http://lodash.com/>
* Build: `lodash -o ./dist/loda Program
registering catch # 393
Potentially unhandled rejection [1] TypeError: object is not a function
at Promise._beget
(/private/tmp/345/node_modules/when/lib/makePromise.js:166:16)
at Promise.then
(/private/tmp/345/node_modules/when/lib/makePromise.js:140:17)
at Promise.catch
(/private/tmp/345/node_modules/when/lib/makePromise.js:156:16)
at Promise.catch.Promise.otherwise
(/private/tmp/345/node_modules/when/lib/decorators/flow.js:37:22)
at /private/tmp/345/test.js:87:24
at next
(/private/tmp/345/node_modules/when/lib/decorators/iterate.js:57:20)
at /private/tmp/345/node_modules/when/lib/decorators/array.js:39:24
at tryCatchReject
(/private/tmp/345/node_modules/when/lib/makePromise.js:838:30)
at runContinuation1
(/private/tmp/345/node_modules/when/lib/makePromise.js:797:4)
at Fulfilled.when
(/private/tmp/345/node_modules/when/lib/makePromise.js:588:4)
at Pending.run
(/private/tmp/345/node_modules/when/lib/makePromise.js:479:13)
#57 reading file with promise: `dist/lodash.compat.min.js`
#57 parsing file: `dist/lodash.compat.min.js`
**
* @license
* Lo-Dash 2.4.1 (Custom Build) lodash.com/license | Underscore.js 1.5.2
underscorejs Program
<end of output, program terminates>
```
### Potential workaround
Note that in at least some cases (not sure about all yet), adding an empty
try/finally as first line of the `_beget` function avoids the failure,
presumably because that either prevents optimization, or changes the
optimization in a way that avoids generating the erroneous compiled code.
```js
Promise.prototype._beget = function() {
try {} finally {};
...
}
```
### References
For more information see the following github issues:
* Original issue report: https://github.com/cujojs/when/issues/345 long,
best to read from bottom up or start here:
https://github.com/cujojs/when/issues/345#issuecomment-51775158
* Followup with test case: https://github.com/cujojs/when/issues/403 by
@anodynos https://github.com/anodynos)
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