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Decipher compiler anomaly for polymorphic copy constructor #74

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jbcoe opened this issue Oct 7, 2023 · 1 comment
Open

Decipher compiler anomaly for polymorphic copy constructor #74

jbcoe opened this issue Oct 7, 2023 · 1 comment

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@jbcoe
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jbcoe commented Oct 7, 2023 •
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See https://godbolt.org/z/75v65MeWY

Behaviour is unexpected, we'd envisaged generated code to be the same (vtable lookup and a method call) - why do we need more indirection?
@jbcoe
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jbcoe commented Oct 8, 2023

A further pared down example from Compiler explorer https://godbolt.org/z/q7jodY5vP seems to suggest that accessing the control block from a (minimal) polymorphic object is not zero-cost.

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