Fix runtime panic for tagged pointers #19
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In some cases, Objective-C may use unaligned pointers. This fix accommodates for such case.
Owner
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Is it possible to force a tagged pointer somehow so we can have a unit test for this? Calling the real ObjC APIs, our tests are macOS only anyways. |
Contributor
Author
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I'll look into it... |
Contributor
Author
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This one is a bit tricky to test, but I think this should work... Note that in the unlikely event that the perquisites for the test are unmet the test is skipped and a warning is logged. |
Owner
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No that’s absolutely excellent work thank you. |
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This fix adds support for tagged pointers, an internal optimization used by the Objective-C runtime for small objects like short
NSStringsandNSNumbers. These “pointers” may not be aligned, as they encode data directly within the pointer value itself.To support tagged pointers safely, the code now explicitly disables Zig’s runtime alignment safety checks when casting such values. This avoids runtime panics caused by misaligned pointer dereferencing.
The issue was observed when interacting with an Objective-C API that returned a
NSString, which turned out to be a tagged pointer (and not a real heap pointer). The previous implementation assumed proper alignment and thus crashed during a cast operation safety check.