Duplicate h$listProps #556
Comments
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We had the same problem at, and we submitted
ghcjs/ghcjs-base#70 as a fix. However, it seems
nobody is tending the PRs upstream at the moment.
…---------- Forwarded message ----------
From: John Lenz <notifications@github.com>
Date: Mon, Dec 19, 2016 at 11:22 AM
Subject: [ghcjs/ghcjs] Duplicate h$listProps (#556)
To: ghcjs/ghcjs <ghcjs@noreply.github.com>
Cc: Subscribed <subscribed@noreply.github.com>
I recently updated ghcjs (8.0 git branch), and started getting
ThreadAborted errors "TypeError: Cannot read property 't' of undefined"
inside the runtime, specifically in the function where h$RTS_580 was
undefined.
function h$e(h$RTS_579)
{
h$r1 = h$RTS_579;
if((typeof h$RTS_579 !== "object"))
{
return h$rs();
};
var h$RTS_580 = h$RTS_579.f;
if((h$RTS_580 === h$unbox_e))
{
h$r1 = h$RTS_579.d1;
return h$rs();
};
switch (h$RTS_580.t)
{
case (2):
case (1):
case (3):
return h$rs();
case (5):
h$p3(h$ap_0_0, h$RTS_579, h$return);
return h$blockOnBlackhole(h$RTS_579);
default:
return h$RTS_580;
};
};
After single-stepping in the chrome debugger, I eventually traced it to the
following problem:
Step 1: I am using the FromJSVal instance for Aeson.Value located in
GHCJS.Marshal, which calls listProps from JavaScript.Object.Internal.
Step 2: listProps is unsafeCoerce (js_listProps o) and js_listProps is a
foreign call to h$listProps
Step 3: h$listProps is defined in https://github.com/ghcjs/
ghcjs-base/blob/master/jsbits/utils.js and properly creates a haskell value
containing the properties of the object. So far everything is great.
Problem!: The shim code also contains a function h$listProps:
https://github.com/ghcjs/shims/blob/master/src/object.js (also in 8.0
branch) This version of h$listProps does not create a haskell value but
just a raw javascript list. If this version of h$listProps is used, the raw
javascript list will be unsafeCoerce into a haskell list which eventually
causes the crash.
Speculation: something in ghcjs changed the order in which code is
generated, which exposed this problem. Before, I suspect that the order in
which code was emitted caused the h$listProps from ghcjs-base to be used,
but some recent change in ghcjs changed the code order and now h$listProps
is being used from shims.
In my generated output, there was only a single call to h$listProps which
was coming from the FromJSVal instance, so I just deleted the shim version
of h$listProps from the generated output and everything started working.
But a long-term fix is to rename one of the functions?
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I don't think that is the correct fix, since it still relies on the order that code is emitted. If ghcjs ever changes the order so that the ghcjs-base version of h$listProps comes later than the shim version of h$listProps, your code will break. |
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That seems to be true, yeah. But in any case, it's a current fix at the moment. The greater issue here though is that all maintainers seem to be MIA. |
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Also found the duplicate h$listProps after single-stepping with chrome debugger. I wish I'd found this issue first! |
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This issue is not exclusive to 8.0. With the lts-6.20 stack resolver this issue is not reproducible for me, but with lts-6.30 it is (both are GHC 7.10.3). |
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This should have been fixed by ghcjs/shims#41 |
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I recently updated ghcjs (8.0 git branch), and started getting ThreadAborted errors "TypeError: Cannot read property 't' of undefined" inside the runtime, specifically in the function where h$RTS_580 was undefined.
After single-stepping in the chrome debugger, I eventually traced it to the following problem:
Step 1: I am using the FromJSVal instance for Aeson.Value located in GHCJS.Marshal, which calls listProps from JavaScript.Object.Internal.
Step 2: listProps is
unsafeCoerce (js_listProps o)andjs_listPropsis a foreign call toh$listPropsStep 3:
h$listPropsis defined in https://github.com/ghcjs/ghcjs-base/blob/master/jsbits/utils.js and properly creates a haskell value containing the properties of the object. So far everything is great.Problem!: The shim code also contains a function
h$listProps: https://github.com/ghcjs/shims/blob/master/src/object.js (also in 8.0 branch) This version ofh$listPropsdoes not create a haskell value but just a raw javascript list. If this version of h$listProps is used, the raw javascript list will be unsafeCoerce into a haskell list which eventually causes the crash.Speculation: something in ghcjs changed the order in which code is generated, which exposed this problem. Before, I suspect that the order in which code was emitted caused the h$listProps from ghcjs-base to be used, but some recent change in ghcjs changed the code order and now h$listProps is being used from shims.
In my generated output, there was only a single call to h$listProps which was coming from the FromJSVal instance, so I just deleted the shim version of h$listProps from the generated output and everything started working. But a long-term fix is to rename one of the functions?
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