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It's possible to cast 0 as extern fn() in safe code #8728

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bluss opened this issue Aug 24, 2013 · 3 comments · Fixed by #9788
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It's possible to cast 0 as extern fn() in safe code #8728

bluss opened this issue Aug 24, 2013 · 3 comments · Fixed by #9788
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A-type-system Area: Type system

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@bluss
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bluss commented Aug 24, 2013

Rust allows casting 0 to a function pointer type like extern "Rust" fn(). This is unsafe.

rusti: let f = 0 as extern "Rust" fn() -> int; f()
-rusti:#rust- application terminated abnormally with signal 11 (Segmentation fault)
@bluss
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bluss commented Aug 24, 2013

dup of #8730

@bluss bluss closed this as completed Aug 24, 2013
@huonw
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huonw commented Aug 24, 2013

Disagree that this is a dup; the other should be made specific to the type inference, since this is a glaring hole and not at all specific to extern "C" fn (like that issue).

cc @nikomatsakis.

@huonw huonw reopened this Aug 24, 2013
@MicahChalmer MicahChalmer mentioned this issue Aug 24, 2013
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@nikomatsakis
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Sounds like a bug all right.

@geoffhill-zz geoffhill-zz mentioned this issue Oct 10, 2013
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bors added a commit that referenced this issue Nov 14, 2013
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auto merge of #9788 : geoffhill/rust/bare-fn-cast, r=pnkfelix
af62adf 
Bare functions are another example of a scalar but non-numeric
type (like char) that should be handled separately in casts.
This disallows expressions like `0 as extern "Rust" fn() -> int;`.

It might be advantageous to allow casts between bare functions
and raw pointers in unsafe code in the future, to pass function
pointers between Rust and C.

Closes #8728
@bors bors closed this as completed in e538c95 Nov 14, 2013
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Typeck: Disallow scalar casts to bare_fn.
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@nikomatsakis @huonw @bluss