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fmt: don't recur if String method (etc.) misbehaves

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Fixes #2555.

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/5486076
This commit is contained in:
Rob Pike 2011-12-14 16:37:54 -08:00
parent 85fdd68bd9
commit 24e9683ae6
2 changed files with 41 additions and 0 deletions
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34
src/pkg/fmt/fmt_test.go
View File

@ -813,3 +813,37 @@ func TestPanics(t *testing.T) {
}
}
}
// Test that erroneous String routine doesn't cause fatal recursion.
var recurCount = 0
type Recur struct {
i int
failed *bool
}
func (r Recur) String() string {
if recurCount++; recurCount > 10 {
*r.failed = true
return "FAIL"
}
// This will call badVerb. Before the fix, that would cause us to recur into
// this routine to print %!p(value). Now we don't call the user's method
// during an error.
return Sprintf("recur@%p value: %d", r, r.i)
}
func TestBadVerbRecursion(t *testing.T) {
failed := false
r := Recur{3, &failed}
Sprintf("recur@%p value: %d\n", &r, r.i)
if failed {
t.Error("fail with pointer")
}
failed = false
r = Recur{4, &failed}
Sprintf("recur@%p, value: %d\n", r, r.i)
if failed {
t.Error("fail with value")
}
}

7
src/pkg/fmt/print.go
View File

@ -74,6 +74,7 @@ type GoStringer interface {
type pp struct {
n int
panicking bool
erroring bool // printing an error condition
buf bytes.Buffer
// field holds the current item, as an interface{}.
field interface{}
@ -124,6 +125,7 @@ var ppFree = newCache(func() interface{} { return new(pp) })
func newPrinter() *pp {
p := ppFree.get().(*pp)
p.panicking = false
p.erroring = false
p.fmt.init(&p.buf)
return p
}
@ -299,6 +301,7 @@ func (p *pp) unknownType(v interface{}) {
}
func (p *pp) badVerb(verb rune) {
p.erroring = true
p.add('%')
p.add('!')
p.add(verb)
@ -316,6 +319,7 @@ func (p *pp) badVerb(verb rune) {
p.buf.Write(nilAngleBytes)
}
p.add(')')
p.erroring = false
}
func (p *pp) fmtBool(v bool, verb rune) {
@ -606,6 +610,9 @@ func (p *pp) catchPanic(field interface{}, verb rune) {
}
func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString, handled bool) {
if p.erroring {
return
}
// Is it a Formatter?
if formatter, ok := p.field.(Formatter); ok {
handled = true