> On Aug 27, 2017, at 10:57 AM, Edward Connell via swift-users
> <swift-users@swift.org> wrote:
>
> import Foundation
>
> class A {
> var counter = 0 {
> // didSet { onSet("counter") } // no leak
> didSet { onSet() } // huge leak
> }
>
> var properties = ["counter" : 0]
> func onSet(_ name: String = #function) {
> properties[name]! += 1
> }
> }
>
> var myclass = A()
>
> for i in 0..<10000000 {
> myclass.counter = i
> }
>
> print(myclass.properties["counter"]!)
The only code generation difference I see, if I modify your didSet to make both
calls is that the compiler treats #function as a UTF-16 literal, whereas
"counter" is recognized as an ASCII literal:
// A.counter.didset
sil hidden @_T03foo1AC7counterSifW : $@convention(method) (Int, @guaranteed A)
-> () {
// %0 // user: %2
// %1 // users: %19, %12, %11, %4,
%3
bb0(%0 : $Int, %1 : $A):
debug_value %0 : $Int, let, name "oldValue", argno 1 // id: %2
debug_value %1 : $A, let, name "self", argno 2 // id: %3
%4 = class_method %1 : $A, #A.onSet!1 : (A) -> (String) -> (),
$@convention(method) (@owned String, @guaranteed A) -> () // user: %11
%5 = string_literal utf8 "counter" // user: %10
%6 = integer_literal $Builtin.Word, 7 // user: %10
%7 = integer_literal $Builtin.Int1, -1 // user: %10
%8 = metatype $@thin String.Type // user: %10
// function_ref String.init(_builtinStringLiteral:utf8CodeUnitCount:isASCII:)
%9 = function_ref
@_T0S2SBp21_builtinStringLiteral_Bw17utf8CodeUnitCountBi1_7isASCIItcfC :
$@convention(method) (Builtin.RawPointer, Builtin.Word, Builtin.Int1, @thin
String.Type) -> @owned String // user: %10
%10 = apply %9(%5, %6, %7, %8) : $@convention(method) (Builtin.RawPointer,
Builtin.Word, Builtin.Int1, @thin String.Type) -> @owned String // user: %11
%11 = apply %4(%10, %1) : $@convention(method) (@owned String, @guaranteed A)
-> ()
%12 = class_method %1 : $A, #A.onSet!1 : (A) -> (String) -> (),
$@convention(method) (@owned String, @guaranteed A) -> () // user: %19
%13 = string_literal utf16 "counter" // user: %18
%14 = integer_literal $Builtin.Word, 7 // user: %18
%15 = integer_literal $Builtin.Int1, -1
%16 = metatype $@thin String.Type // user: %18
// function_ref String.init(_builtinUTF16StringLiteral:utf16CodeUnitCount:)
%17 = function_ref
@_T0S2SBp26_builtinUTF16StringLiteral_Bw18utf16CodeUnitCounttcfC :
$@convention(method) (Builtin.RawPointer, Builtin.Word, @thin String.Type) ->
@owned String // user: %18
%18 = apply %17(%13, %14, %16) : $@convention(method) (Builtin.RawPointer,
Builtin.Word, @thin String.Type) -> @owned String // user: %19
%19 = apply %12(%18, %1) : $@convention(method) (@owned String, @guaranteed
A) -> ()
%20 = tuple () // user: %21
return %20 : $() // id: %21
} // end sil function '_T03foo1AC7counterSifW'
Michael, could there be a leak in the implementation of
String(_builtinUTF16StringLiteral:utf16CodeUnitCount:)? The SIL at first glance
looks balanced here.
-Joe
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