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Previously, the unified frontend implemented unsafe.Sizeof, etc that involved derived types by constructing a normal OSIZEOF, etc expression, including fully instantiating their argument. (When unsafe.Sizeof is applied to a non-generic type, types2 handles constant folding it.) This worked, but involves unnecessary work, since all we really need to track is the argument type (and the field selections, for unsafe.Offsetof). Further, the argument expression could generate temporary variables, which would then go unused after typecheck replaced the OSIZEOF expression with an OLITERAL. This results in compiler failures after CL 523315, which made later passes stricter about expecting the frontend to not construct unused temporaries. Fixes #62515. Change-Id: I37baed048fd2e35648c59243f66c97c24413aa94 Reviewed-on: https://go-review.googlesource.com/c/go/+/527097 Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com> Auto-Submit: Matthew Dempsky <mdempsky@google.com>
28 lines
592 B
Go
28 lines
592 B
Go
// compile
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// Copyright 2023 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Unified frontend generated unnecessary temporaries for expressions
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// within unsafe.Sizeof, etc functions.
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package main
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import "unsafe"
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func F[G int](g G) (uintptr, uintptr, uintptr) {
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var c chan func() int
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type s struct {
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g G
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x []int
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}
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return unsafe.Sizeof(s{g, make([]int, (<-c)())}),
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unsafe.Alignof(s{g, make([]int, (<-c)())}),
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unsafe.Offsetof(s{g, make([]int, (<-c)())}.x)
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}
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func main() {
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F(0)
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}
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