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fix bug in prefix code: must stop one character before any potential match of an empty string

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Fixes #308.

R=rsc
CC=golang-dev
https://golang.org/cl/157142
This commit is contained in:
Rob Pike 2009-11-23 14:06:21 -08:00
parent b050a1b223
commit 3b7f552fbb
2 changed files with 8 additions and 3 deletions
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2
src/pkg/regexp/all_test.go
View file

@ -95,6 +95,8 @@ var matches = []tester{
tester{`a*(|(b))c*`, "aacc", vec{0, 4, 2, 2, -1, -1}}, tester{`a*(|(b))c*`, "aacc", vec{0, 4, 2, 2, -1, -1}},
tester{`(.*).*`, "ab", vec{0, 2, 0, 2}}, tester{`(.*).*`, "ab", vec{0, 2, 0, 2}},
tester{`[.]`, ".", vec{0, 1}}, tester{`[.]`, ".", vec{0, 1}},
tester{`/$`, "/abc/", vec{4, 5}},
tester{`/$`, "/abc", vec{}},
} }
func compileTest(t *testing.T, expr string, error os.Error) *Regexp { func compileTest(t *testing.T, expr string, error os.Error) *Regexp {

9
src/pkg/regexp/regexp.go
View file

@ -633,15 +633,18 @@ func (re *Regexp) setPrefix() {
var utf = make([]byte, utf8.UTFMax); var utf = make([]byte, utf8.UTFMax);
// First instruction is start; skip that. // First instruction is start; skip that.
i := re.inst.At(0).(instr).next().index(); i := re.inst.At(0).(instr).next().index();
Loop:
for i < re.inst.Len() { for i < re.inst.Len() {
inst := re.inst.At(i).(instr); inst := re.inst.At(i).(instr);
// stop if this is not a char // stop if this is not a char
if inst.kind() != _CHAR { if inst.kind() != _CHAR {
break break
} }
// stop if this char starts a closure; liberal but easy test: is an ALT next? // stop if this char can be followed by a match for an empty string,
if re.inst.At(inst.next().index()).(instr).kind() == _ALT { // which includes closures, ^, and $.
break switch re.inst.At(inst.next().index()).(instr).kind() {
case _BOT, _EOT, _ALT:
break Loop
} }
n := utf8.EncodeRune(inst.(*_Char).char, utf); n := utf8.EncodeRune(inst.(*_Char).char, utf);
b = bytes.Add(b, utf[0:n]); b = bytes.Add(b, utf[0:n]);