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cmd/compile: fix escape analysis of string min/max
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When I was plumbing min/max support through the compiler, I was
thinking mostly about numeric argument types. As a result, I forgot
that escape analysis would need to be aware that min/max can operate
on string values, which contain pointers.

Fixes #64565.

Change-Id: I36127ce5a2da942401910fa0f9de922726c9f94d
Reviewed-on: https://go-review.googlesource.com/c/go/+/547715
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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mdempsky authored and gopherbot committed Dec 5, 2023
1 parent ed30ee6 commit 34416d7
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Showing 4 changed files with 35 additions and 3 deletions.
13 changes: 10 additions & 3 deletions src/cmd/compile/internal/escape/call.go
Original file line number Diff line number Diff line change
Expand Up @@ -155,10 +155,17 @@ func (e *escape) call(ks []hole, call ir.Node) {
e.discard(call.X)
e.discard(call.Y)

case ir.ODELETE, ir.OMAX, ir.OMIN, ir.OPRINT, ir.OPRINTLN, ir.ORECOVERFP:
case ir.ODELETE, ir.OPRINT, ir.OPRINTLN, ir.ORECOVERFP:
call := call.(*ir.CallExpr)
for i := range call.Args {
e.discard(call.Args[i])
for _, arg := range call.Args {
e.discard(arg)
}
e.discard(call.RType)

case ir.OMIN, ir.OMAX:
call := call.(*ir.CallExpr)
for _, arg := range call.Args {
argument(ks[0], arg)
}
e.discard(call.RType)

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7 changes: 7 additions & 0 deletions test/escape_calls.go
Original file line number Diff line number Diff line change
Expand Up @@ -52,3 +52,10 @@ func bar() {
s := "string"
f([]string{s}) // ERROR "\[\]string{...} escapes to heap"
}

func strmin(a, b, c string) string { // ERROR "leaking param: a to result ~r0 level=0" "leaking param: b to result ~r0 level=0" "leaking param: c to result ~r0 level=0"
return min(a, b, c)
}
func strmax(a, b, c string) string { // ERROR "leaking param: a to result ~r0 level=0" "leaking param: b to result ~r0 level=0" "leaking param: c to result ~r0 level=0"
return max(a, b, c)
}
15 changes: 15 additions & 0 deletions test/fixedbugs/issue64565.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
// run

// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

func main() {
m := "0"
for _, c := range "321" {
m = max(string(c), m)
println(m)
}
}
3 changes: 3 additions & 0 deletions test/fixedbugs/issue64565.out
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
3
3
3

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