regexp: document and implement that invalid UTF-8 bytes are the same as U+FFFD
What should it mean to run a regexp match on invalid UTF-8 bytes?
The coherent behavior options are:
1. Invalid UTF-8 does not match any character classes,
nor a U+FFFD literal (nor \x{fffd}).
2. Each byte of invalid UTF-8 is treated identically to a U+FFFD in the input,
as a utf8.DecodeRune loop might.
RE2 uses Rule 1.
Because it works byte at a time, it can also provide \C to match any
single byte of input, which matches invalid UTF-8 as well.
This provides the nice property that a match for a regexp without \C
is guaranteed to be valid UTF-8.
Unfortunately, today Go has an incoherent mix of these two, although
mostly Rule 2. This is a deviation from RE2, and it gives up the nice
property, but we probably can't correct that at this point.
In particular .* already matches entire inputs today, valid UTF-8 or
not, and I doubt we can break that.
This CL adopts Rule 2 officially, fixing the few places that deviate from it.
Fixes #48749.
Change-Id: I96402527c5dfb1146212f568ffa09dde91d71244
Reviewed-on: https://go-review.googlesource.com/c/go/+/354569
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/src/regexp/all_test.go b/src/regexp/all_test.go
index be7a2e7..c233cfa 100644
--- a/src/regexp/all_test.go
+++ b/src/regexp/all_test.go
@@ -372,6 +372,9 @@
{`^^0$$`, ``, ``, false},
{`^$^$`, ``, ``, false},
{`$$0^^`, ``, ``, false},
+ {`a\x{fffd}b`, ``, `a`, false},
+ {`\x{fffd}b`, ``, ``, false},
+ {"\ufffd", ``, ``, false},
}
func TestQuoteMeta(t *testing.T) {
diff --git a/src/regexp/find_test.go b/src/regexp/find_test.go
index 64c2239..2edbe9b 100644
--- a/src/regexp/find_test.go
+++ b/src/regexp/find_test.go
@@ -116,6 +116,13 @@
{"\\`", "`", build(1, 0, 1)},
{"[\\`]+", "`", build(1, 0, 1)},
+ {"\ufffd", "\xff", build(1, 0, 1)},
+ {"\ufffd", "hello\xffworld", build(1, 5, 6)},
+ {`.*`, "hello\xffworld", build(1, 0, 11)},
+ {`\x{fffd}`, "\xc2\x00", build(1, 0, 1)},
+ {"[\ufffd]", "\xff", build(1, 0, 1)},
+ {`[\x{fffd}]`, "\xc2\x00", build(1, 0, 1)},
+
// long set of matches (longer than startSize)
{
".",
diff --git a/src/regexp/onepass.go b/src/regexp/onepass.go
index 2f3ce6f..bc47f4c 100644
--- a/src/regexp/onepass.go
+++ b/src/regexp/onepass.go
@@ -9,6 +9,7 @@
"sort"
"strings"
"unicode"
+ "unicode/utf8"
)
// "One-pass" regexp execution.
@@ -55,7 +56,7 @@
// Have prefix; gather characters.
var buf strings.Builder
- for iop(i) == syntax.InstRune && len(i.Rune) == 1 && syntax.Flags(i.Arg)&syntax.FoldCase == 0 {
+ for iop(i) == syntax.InstRune && len(i.Rune) == 1 && syntax.Flags(i.Arg)&syntax.FoldCase == 0 && i.Rune[0] != utf8.RuneError {
buf.WriteRune(i.Rune[0])
pc, i = i.Out, &p.Inst[i.Out]
}
diff --git a/src/regexp/regexp.go b/src/regexp/regexp.go
index bfcf791..af7259c 100644
--- a/src/regexp/regexp.go
+++ b/src/regexp/regexp.go
@@ -20,6 +20,8 @@
// or any book about automata theory.
//
// All characters are UTF-8-encoded code points.
+// Following utf8.DecodeRune, each byte of an invalid UTF-8 sequence
+// is treated as if it encoded utf8.RuneError (U+FFFD).
//
// There are 16 methods of Regexp that match a regular expression and identify
// the matched text. Their names are matched by this regular expression:
@@ -276,7 +278,11 @@
case syntax.OpLiteral:
l := 0
for _, r := range re.Rune {
- l += utf8.RuneLen(r)
+ if r == utf8.RuneError {
+ l++
+ } else {
+ l += utf8.RuneLen(r)
+ }
}
return l
case syntax.OpCapture, syntax.OpPlus:
diff --git a/src/regexp/syntax/prog.go b/src/regexp/syntax/prog.go
index ae7a9a2..8583f55e 100644
--- a/src/regexp/syntax/prog.go
+++ b/src/regexp/syntax/prog.go
@@ -8,6 +8,7 @@
"strconv"
"strings"
"unicode"
+ "unicode/utf8"
)
// Compiled program.
@@ -154,7 +155,7 @@
// Have prefix; gather characters.
var buf strings.Builder
- for i.op() == InstRune && len(i.Rune) == 1 && Flags(i.Arg)&FoldCase == 0 {
+ for i.op() == InstRune && len(i.Rune) == 1 && Flags(i.Arg)&FoldCase == 0 && i.Rune[0] != utf8.RuneError {
buf.WriteRune(i.Rune[0])
i = p.skipNop(i.Out)
}
