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When compiling concurrently, we walk all functions before compiling any of them. Walking functions can cause variables to switch from being non-addrtaken to addrtaken, e.g. to prepare for a runtime call. Typechecking propagates addrtaken-ness of closure variables to their outer variables, so that capturevars can decide whether to pass the variable's value or a pointer to it. When all functions are compiled immediately, as long as the containing function is compiled prior to the closure, this propagation has no effect. When compilation is deferred, though, in rare cases, this results in a change in the addrtaken-ness of a variable in the outer function, which in turn changes the compiler's output. (This is rare because in a great many cases, a temporary has been introduced, insulating the outer variable from modification.) But concurrent compilation must generate identical results. To fix this, track whether capturevars has run. If it has, there is no need to update outer variables when closure variables change. Capturevars always runs before any functions are walked or compiled. The remainder of the changes in this CL are to support the test. In particular, -d=compilelater forces the compiler to walk all functions before compiling any of them, despite being non-concurrent. This is useful because -live is fundamentally incompatible with concurrent compilation, but we want -c=1 to have no behavior changes. Fixes #20250 Change-Id: I89bcb54268a41e8588af1ac8cc37fbef856a90c2 Reviewed-on: https://go-review.googlesource.com/42853 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
25 lines
713 B
Go
25 lines
713 B
Go
// errorcheck -0 -live -d=compilelater
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// Copyright 2017 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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// Issue 20250: liveness differed with concurrent compilation
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// due to propagation of addrtaken to outer variables for
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// closure variables.
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package p
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type T struct {
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s string
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}
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func f(a T) { // ERROR "live at entry to f: a"
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var e interface{}
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func() { // ERROR "live at entry to f.func1: &e a"
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e = a.s // ERROR "live at call to convT2Estring: &e a" "live at call to writebarrierptr: a"
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}() // ERROR "live at call to f.func1: e$"
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// Before the fix, both a and e were live at the previous line.
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_ = e
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}
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