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initial pass at function pointers #45

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Jan 31, 2019
Merged

initial pass at function pointers #45

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4285e50
initial pass at function pointers
ubsan Nov 5, 2018
95669d8
minor nits
ubsan Nov 5, 2018
7a19f00
add a >
ubsan Nov 6, 2018
2132500
correct lifetime stuff
ubsan Jan 11, 2019
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11 changes: 10 additions & 1 deletion reference/src/representation/function-pointers.md
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Expand Up @@ -8,7 +8,16 @@ In Rust, a function pointer type, is either `fn(Args...) -> Ret`,
A function pointer is the address of a function,
and has function pointer type.
The pointer is implicit in the `fn` type,
and `fn` types are implicitly `'static`.
and they have no lifetime of their own;
therefore, function pointers are assumed to point to
a block of code with static lifetime.
This is not necessarily always true,
since, for example, you can unload a dynamic library.
Therefore, this is _only_ a safety invariant,
not a validity invariant;
as long as one doesn't call a function pointer which points to freed memory,
it is not undefined behavior.
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I'd just say something like: "Function pointers have no lifetime. They must point to an allocated block of code when being called."

The rest of this belongs to #72, doesn't it?



In C, a function pointer type is `Ret (*)(Args...)`, or `Ret ABI (*)(Args...)`,
and values of function pointer type are either a null pointer value,
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