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package flaws
import (
"testing"
)
func BenchmarkLiteralFunctions(b *testing.B) {
for i := 0; i < b.N; i++ {
var y1 int
foo(&y1, 42) // GOOD: y1 does not escape
var y2 int
func(p *int, x int) {
*p = x
}(&y2, 42) // BAD: Cause of y2 escape
var y3 int
p := foo
p(&y3, 42) // BAD: Cause of y3 escape
}
}
func foo(p *int, x int) {
*p = x
}
/*
$ go test -gcflags "-m -m" -run none -bench BenchmarkLiteralFunctions -benchmem -memprofile mem.out
# github.com/ardanlabs/gotraining/topics/go/language/pointers/flaws/example2
./example2_test.go:21:6: can inline foo as: func(*int, int) { *p = x }
./example2_test.go:5:6: cannot inline BenchmarkLiteralFunctions: unhandled op for
./example2_test.go:8:6: inlining call to foo func(*int, int) { *p = x }
./example2_test.go:11:3: can inline BenchmarkLiteralFunctions.func1 as: func(*int, int) { *p = x }
./example2_test.go:13:5: &y2 escapes to heap
./example2_test.go:13:5: from (func literal)(&y2, 42) (parameter to indirect call) at ./example2_test.go:13:4
./example2_test.go:10:7: moved to heap: y2
./example2_test.go:17:5: &y3 escapes to heap
./example2_test.go:17:5: from p(&y3, 42) (parameter to indirect call) at ./example2_test.go:17:4
./example2_test.go:15:7: moved to heap: y3
./example2_test.go:5:35: BenchmarkLiteralFunctions b does not escape
./example2_test.go:8:7: BenchmarkLiteralFunctions &y1 does not escape
./example2_test.go:11:3: BenchmarkLiteralFunctions func literal does not escape
./example2_test.go:11:18: BenchmarkLiteralFunctions.func1 p does not escape
./example2_test.go:21:20: foo p does not escape
goos: darwin
goarch: amd64
pkg: github.com/ardanlabs/gotraining/topics/go/language/pointers/flaws/example2
BenchmarkLiteralFunctions-8 50000000 30.7 ns/op 16 B/op 2 allocs/op
$ go tool pprof -alloc_space mem.out
Type: alloc_space
(pprof) list Benchmark
Total: 768.01MB
ROUTINE ======================== github.com/ardanlabs/gotraining/topics/go/language/pointers/flaws/example2.BenchmarkLiteralFunctions in /Users/bill/code/go/src/github.com/ardanlabs/gotraining/topics/go/language/pointers/flaws/example2/example2_test.go
768.01MB 768.01MB (flat, cum) 100% of Total
. . 5:func BenchmarkLiteralFunctions(b *testing.B) {
. . 6: for i := 0; i < b.N; i++ {
. . 7: var y1 int
. . 8: foo(&y1, 42) // GOOD: y1 does not escape
. . 9:
380.51MB 380.51MB 10: var y2 int
. . 11: func(p *int, x int) {
. . 12: *p = x
. . 13: }(&y2, 42) // BAD: Cause of y2 escape
. . 14:
387.51MB 387.51MB 15: var y3 int
. . 16: p := foo
. . 17: p(&y3, 42) // BAD: Cause of y3 escape
. . 18: }
. . 19:}
*/
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