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[SR-13180] withUnsafePointer should guarantee pointer stability for globals and class properties #55621

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atrick opened this issue Jul 8, 2020 · 0 comments

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atrick commented Jul 8, 2020

Previous ID SR-13180
Radar None
Original Reporter @atrick
Type Bug
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: f898da4d21aaa0b9abd17b57883351ec

Issue Description:

We should provide a guarantee of pointer stability not just within the `withUnsafePointer` closure, but also with across multiple calls with `withUnsafePointer`, `@inout` arguments, and C functions that access the same global.

For example:

C code:

struct MyStruct {
 int field;
};
extern const struct MyStruct myGlobal;
void takePointer(const struct MyStruct *);

Swift code

withUnsafePointer(to: myGlobal) {
 takePointer($0)
}

The implementation should guarantee that the pointer passed to `takePointer` is the address of `myGlobal`:

$0 == &myGlobal

I think this rule should apply to globals and class properties. @lorentey also proposed a "stable storage" language extension, so there might be some overlap with that.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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