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cmd/compile: fix unnamed parameter handling in escape analysis
For recursive functions, the parameters were iterated using fn.Name.Defn.Func.Dcl, which does not include unnamed/blank parameters. This results in a mismatch in formal-actual assignments, for example, func f(_ T, x T) f(a, b) should result in { _=a, x=b }, but the escape analysis currently sees only { x=a } and drops b on the floor. This may cause b to not escape when it should (or a escape when it should not). Fix this by using fntype.Params().FieldSlice() instead, which does include unnamed parameters. Also add a sanity check that ensures all the actual parameters are consumed. Fixes #29000 Change-Id: Icd86f2b5d71e7ebbab76e375b7702f62efcf59ae Reviewed-on: https://go-review.googlesource.com/c/152617 Reviewed-by: Keith Randall <khr@golang.org>
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@ -1652,49 +1652,79 @@ func (e *EscState) esccall(call *Node, parent *Node) {
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Fatalf("graph inconsistency")
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}
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sawRcvr := false
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for _, n := range fn.Name.Defn.Func.Dcl {
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switch n.Class() {
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case PPARAM:
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if call.Op != OCALLFUNC && !sawRcvr {
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e.escassignWhyWhere(n, call.Left.Left, "call receiver", call)
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sawRcvr = true
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continue
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}
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if len(args) == 0 {
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continue
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}
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arg := args[0]
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if n.IsDDD() && !call.IsDDD() {
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// Introduce ODDDARG node to represent ... allocation.
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arg = nod(ODDDARG, nil, nil)
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arr := types.NewArray(n.Type.Elem(), int64(len(args)))
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arg.Type = types.NewPtr(arr) // make pointer so it will be tracked
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arg.Pos = call.Pos
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e.track(arg)
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call.Right = arg
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}
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e.escassignWhyWhere(n, arg, "arg to recursive call", call) // TODO this message needs help.
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if arg == args[0] {
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args = args[1:]
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continue
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}
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// "..." arguments are untracked
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for _, a := range args {
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if Debug['m'] > 3 {
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fmt.Printf("%v::esccall:: ... <- %S, untracked\n", linestr(lineno), a)
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}
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e.escassignSinkWhyWhere(arg, a, "... arg to recursive call", call)
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}
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// No more PPARAM processing, but keep
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// going for PPARAMOUT.
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args = nil
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i := 0
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case PPARAMOUT:
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// Receiver.
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if call.Op != OCALLFUNC {
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rf := fntype.Recv()
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if rf.Sym != nil && !rf.Sym.IsBlank() {
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n := fn.Name.Defn.Func.Dcl[0]
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i++
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if n.Class() != PPARAM {
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Fatalf("esccall: not a parameter %+v", n)
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}
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e.escassignWhyWhere(n, call.Left.Left, "recursive call receiver", call)
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}
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}
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// Parameters.
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for _, param := range fntype.Params().FieldSlice() {
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if param.Sym == nil || param.Sym.IsBlank() {
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// Unnamed parameter is not listed in Func.Dcl.
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// But we need to consume the arg.
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if param.IsDDD() && !call.IsDDD() {
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args = nil
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} else {
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args = args[1:]
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}
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continue
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}
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n := fn.Name.Defn.Func.Dcl[i]
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i++
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if n.Class() != PPARAM {
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Fatalf("esccall: not a parameter %+v", n)
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}
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if len(args) == 0 {
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continue
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}
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arg := args[0]
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if n.IsDDD() && !call.IsDDD() {
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// Introduce ODDDARG node to represent ... allocation.
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arg = nod(ODDDARG, nil, nil)
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arr := types.NewArray(n.Type.Elem(), int64(len(args)))
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arg.Type = types.NewPtr(arr) // make pointer so it will be tracked
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arg.Pos = call.Pos
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e.track(arg)
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call.Right = arg
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}
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e.escassignWhyWhere(n, arg, "arg to recursive call", call) // TODO this message needs help.
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if arg == args[0] {
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args = args[1:]
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continue
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}
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// "..." arguments are untracked
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for _, a := range args {
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if Debug['m'] > 3 {
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fmt.Printf("%v::esccall:: ... <- %S, untracked\n", linestr(lineno), a)
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}
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e.escassignSinkWhyWhere(arg, a, "... arg to recursive call", call)
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}
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// ... arg consumes all remaining arguments
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args = nil
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}
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// Results.
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for _, n := range fn.Name.Defn.Func.Dcl[i:] {
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if n.Class() == PPARAMOUT {
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cE.Retval.Append(n)
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}
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}
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// Sanity check: all arguments must be consumed.
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if len(args) != 0 {
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Fatalf("esccall not consumed all args %+v\n", call)
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}
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return
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}
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@ -228,3 +228,20 @@ func f15730c(args ...interface{}) { // ERROR "leaking param content: args"
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}
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}
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}
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// Issue 29000: unnamed parameter is not handled correctly
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var sink4 interface{}
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var alwaysFalse = false
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func f29000(_ int, x interface{}) { // ERROR "leaking param: x"
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sink4 = x
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if alwaysFalse {
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g29000()
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}
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}
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func g29000() {
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x := 1
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f29000(2, x) // ERROR "x escapes to heap"
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}
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