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cmd/compile: report block start for gotos jumping into blocks
Follow-up on https://go-review.googlesource.com/#/c/39998/ which dropped this information. The reported blocks are the innermost blocks containing a label jumped to from outside, not the outermost block as reported originally by cmd/compile. We could report the outermost block with a slighly more involved algorithm (need to track containing blocks for all unresolved forward gotos), but since gccgo also reports the innermost blocks, the current approach seems good enough. Change-Id: Ic0235b8fafe8d5f99dc9872b58e90e8d9e72c5db Reviewed-on: https://go-review.googlesource.com/40980 Run-TryBot: Robert Griesemer <gri@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Robert Griesemer
parent
08fe56386b
commit
bb70f517e9
@ -25,21 +25,19 @@ func checkBranches(body *BlockStmt, errh ErrorHandler) {
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// scope of all labels in this body
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ls := &labelScope{errh: errh}
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fwdGo2s := ls.blockBranches(nil, 0, nil, body.List)
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fwdGo2s := ls.blockBranches(nil, 0, nil, body.Pos(), body.List)
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// If there are any forward gotos left, no matching label was
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// found for them. Either those labels were never defined, or
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// they are inside blocks and not reachable from the gotos.
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for _, go2 := range fwdGo2s {
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var msg string
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name := go2.Label.Value
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if alt, found := ls.labels[name]; found {
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msg = "goto %s jumps into block"
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alt.used = true // avoid "defined and not used" error
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if l := ls.labels[name]; l != nil {
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l.used = true // avoid "defined and not used" error
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ls.err(go2.Label.Pos(), "goto %s jumps into block starting at %s", name, l.parent.start)
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} else {
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msg = "label %s not defined"
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ls.err(go2.Label.Pos(), "label %s not defined", name)
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}
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ls.err(go2.Label.Pos(), msg, name)
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}
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// spec: "It is illegal to define a label that is never used."
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@ -64,7 +62,8 @@ type label struct {
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type block struct {
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parent *block // immediately enclosing block, or nil
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lstmt *LabeledStmt // labeled statement to which this block belongs, or nil
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start src.Pos // start of block
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lstmt *LabeledStmt // labeled statement associated with this block, or nil
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}
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func (ls *labelScope) err(pos src.Pos, format string, args ...interface{}) {
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@ -128,11 +127,12 @@ const (
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continueOk
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)
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// blockBranches processes a block's body and returns the list of unresolved (forward) gotos.
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// parent is the immediately enclosing block (or nil), context provides information about the
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// enclosing statements, and lstmt is the labeled statement this body belongs to, or nil.
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func (ls *labelScope) blockBranches(parent *block, context uint, lstmt *LabeledStmt, body []Stmt) []*BranchStmt {
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b := &block{parent: parent, lstmt: lstmt}
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// blockBranches processes a block's body starting at start and returns the
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// list of unresolved (forward) gotos. parent is the immediately enclosing
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// block (or nil), context provides information about the enclosing statements,
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// and lstmt is the labeled statement asociated with this block, or nil.
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func (ls *labelScope) blockBranches(parent *block, context uint, lstmt *LabeledStmt, start src.Pos, body []Stmt) []*BranchStmt {
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b := &block{parent: parent, start: start, lstmt: lstmt}
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var varPos src.Pos
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var varName Expr
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@ -159,8 +159,8 @@ func (ls *labelScope) blockBranches(parent *block, context uint, lstmt *LabeledS
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return false
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}
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innerBlock := func(flags uint, body []Stmt) {
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fwdGo2s = append(fwdGo2s, ls.blockBranches(b, context|flags, lstmt, body)...)
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innerBlock := func(flags uint, start src.Pos, body []Stmt) {
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fwdGo2s = append(fwdGo2s, ls.blockBranches(b, context|flags, lstmt, start, body)...)
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}
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for _, stmt := range body {
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@ -277,25 +277,25 @@ func (ls *labelScope) blockBranches(parent *block, context uint, lstmt *LabeledS
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case *BlockStmt:
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// Unresolved forward gotos from the nested block
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// become forward gotos for the current block.
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innerBlock(0, s.List)
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innerBlock(0, s.Pos(), s.List)
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case *IfStmt:
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innerBlock(0, s.Then.List)
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innerBlock(0, s.Then.Pos(), s.Then.List)
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if s.Else != nil {
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innerBlock(0, []Stmt{s.Else})
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innerBlock(0, s.Else.Pos(), []Stmt{s.Else})
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}
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case *ForStmt:
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innerBlock(breakOk|continueOk, s.Body.List)
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innerBlock(breakOk|continueOk, s.Body.Pos(), s.Body.List)
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case *SwitchStmt:
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for _, cc := range s.Body {
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innerBlock(breakOk, cc.Body)
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innerBlock(breakOk, cc.Pos(), cc.Body)
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}
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case *SelectStmt:
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for _, cc := range s.Body {
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innerBlock(breakOk, cc.Body)
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innerBlock(breakOk, cc.Pos(), cc.Body)
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}
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}
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}
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64
test/goto.go
64
test/goto.go
@ -77,7 +77,7 @@ L:
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// error shows first offending variable
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func _() {
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goto L // ERROR "goto L jumps over declaration of x at LINE+1|goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
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goto L // ERROR "goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
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x := 1 // GCCGO_ERROR "defined here"
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_ = x
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y := 1
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@ -87,7 +87,7 @@ L:
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// goto not okay even if code path is dead
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func _() {
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goto L // ERROR "goto L jumps over declaration of x at LINE+1|goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
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goto L // ERROR "goto L jumps over declaration of y at LINE+3|goto jumps over declaration"
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x := 1 // GCCGO_ERROR "defined here"
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_ = x
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y := 1
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@ -114,7 +114,7 @@ L:
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// goto into inner block not okay
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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{ // GCCGO_ERROR "block starts here"
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L:
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}
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@ -125,12 +125,12 @@ func _() {
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{ // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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// error shows first (outermost) offending block
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto jumps into block"
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{
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{
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{ // GCCGO_ERROR "block starts here"
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@ -142,7 +142,7 @@ func _() {
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// error prefers block diagnostic over declaration diagnostic
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto jumps into block"
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x := 1
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_ = x
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{ // GCCGO_ERROR "block starts here"
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@ -179,14 +179,14 @@ L:
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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if true { // GCCGO_ERROR "block starts here"
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L:
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}
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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if true { // GCCGO_ERROR "block starts here"
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L:
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} else {
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@ -194,7 +194,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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if true {
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} else { // GCCGO_ERROR "block starts here"
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L:
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@ -205,13 +205,13 @@ func _() {
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if false { // GCCGO_ERROR "block starts here"
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L:
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} else {
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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}
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func _() {
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if true {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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} else { // GCCGO_ERROR "block starts here"
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L:
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}
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@ -219,7 +219,7 @@ func _() {
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func _() {
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if true {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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} else if false { // GCCGO_ERROR "block starts here"
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L:
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}
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@ -227,7 +227,7 @@ func _() {
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func _() {
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if true {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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} else if false { // GCCGO_ERROR "block starts here"
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L:
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} else {
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@ -241,7 +241,7 @@ func _() {
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// really is LINE+1 (like in the previous test),
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// even though it looks like it might be LINE+3 instead.
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if true {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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} else if false {
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} else { // GCCGO_ERROR "block starts here"
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L:
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@ -290,7 +290,7 @@ func _() {
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for { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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@ -299,49 +299,49 @@ func _() {
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L1:
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}
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L:
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goto L1 // ERROR "goto L1 jumps into block starting at LINE-5|goto L1 jumps into block|goto jumps into block"
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goto L1 // ERROR "goto L1 jumps into block starting at LINE-5|goto jumps into block"
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}
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func _() {
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for i < n { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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for i = 0; i < n; i++ { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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for i = range x { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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for i = range c { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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for i = range m { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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func _() {
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for i = range s { // GCCGO_ERROR "block starts here"
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L:
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}
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-3|goto jumps into block"
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}
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// switch
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@ -395,7 +395,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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switch i {
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case 0:
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L: // GCCGO_ERROR "block starts here"
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@ -403,7 +403,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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switch i {
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case 0:
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L: // GCCGO_ERROR "block starts here"
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@ -413,7 +413,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto jumps into block"
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switch i {
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case 0:
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default:
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@ -424,7 +424,7 @@ func _() {
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func _() {
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switch i {
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default:
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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case 0:
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L: // GCCGO_ERROR "block starts here"
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}
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@ -436,7 +436,7 @@ func _() {
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L: // GCCGO_ERROR "block starts here"
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;
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default:
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goto L // ERROR "goto L jumps into block starting at LINE-4|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-4|goto jumps into block"
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}
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}
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@ -492,7 +492,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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select {
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case c <- 1:
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L: // GCCGO_ERROR "block starts here"
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@ -500,7 +500,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+2|goto jumps into block"
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select {
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case c <- 1:
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L: // GCCGO_ERROR "block starts here"
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@ -510,7 +510,7 @@ func _() {
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}
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func _() {
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+3|goto jumps into block"
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select {
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case <-c:
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default:
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@ -521,7 +521,7 @@ func _() {
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func _() {
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select {
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default:
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE+1|goto jumps into block"
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case <-c:
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L: // GCCGO_ERROR "block starts here"
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}
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@ -533,6 +533,6 @@ func _() {
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L: // GCCGO_ERROR "block starts here"
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;
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default:
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goto L // ERROR "goto L jumps into block starting at LINE-4|goto L jumps into block|goto jumps into block"
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goto L // ERROR "goto L jumps into block starting at LINE-4|goto jumps into block"
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}
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}
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