Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 748 insertions, 0 deletions

diff --git a/src/regexp/exec_test.go b/src/regexp/exec_test.go
new file mode 100644
index 0000000..5f84426
--- /dev/null
+++ b/src/regexp/exec_test.go
@@ -0,0 +1,748 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package regexp
+
+import (
+	"bufio"
+	"compress/bzip2"
+	"fmt"
+	"internal/testenv"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp/syntax"
+	"strconv"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+// TestRE2 tests this package's regexp API against test cases
+// considered during RE2's exhaustive tests, which run all possible
+// regexps over a given set of atoms and operators, up to a given
+// complexity, over all possible strings over a given alphabet,
+// up to a given size. Rather than try to link with RE2, we read a
+// log file containing the test cases and the expected matches.
+// The log file, re2-exhaustive.txt, is generated by running 'make log'
+// in the open source RE2 distribution https://github.com/google/re2/.
+//
+// The test file format is a sequence of stanzas like:
+//
+//	strings
+//	"abc"
+//	"123x"
+//	regexps
+//	"[a-z]+"
+//	0-3;0-3
+//	-;-
+//	"([0-9])([0-9])([0-9])"
+//	-;-
+//	-;0-3 0-1 1-2 2-3
+//
+// The stanza begins by defining a set of strings, quoted
+// using Go double-quote syntax, one per line. Then the
+// regexps section gives a sequence of regexps to run on
+// the strings. In the block that follows a regexp, each line
+// gives the semicolon-separated match results of running
+// the regexp on the corresponding string.
+// Each match result is either a single -, meaning no match, or a
+// space-separated sequence of pairs giving the match and
+// submatch indices. An unmatched subexpression formats
+// its pair as a single - (not illustrated above).  For now
+// each regexp run produces two match results, one for a
+// ``full match'' that restricts the regexp to matching the entire
+// string or nothing, and one for a ``partial match'' that gives
+// the leftmost first match found in the string.
+//
+// Lines beginning with # are comments. Lines beginning with
+// a capital letter are test names printed during RE2's test suite
+// and are echoed into t but otherwise ignored.
+//
+// At time of writing, re2-exhaustive.txt is 59 MB but compresses to 385 kB,
+// so we store re2-exhaustive.txt.bz2 in the repository and decompress it on the fly.
+//
+func TestRE2Search(t *testing.T) {
+	testRE2(t, "testdata/re2-search.txt")
+}
+
+func testRE2(t *testing.T, file string) {
+	f, err := os.Open(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	var txt io.Reader
+	if strings.HasSuffix(file, ".bz2") {
+		z := bzip2.NewReader(f)
+		txt = z
+		file = file[:len(file)-len(".bz2")] // for error messages
+	} else {
+		txt = f
+	}
+	lineno := 0
+	scanner := bufio.NewScanner(txt)
+	var (
+		str       []string
+		input     []string
+		inStrings bool
+		re        *Regexp
+		refull    *Regexp
+		nfail     int
+		ncase     int
+	)
+	for lineno := 1; scanner.Scan(); lineno++ {
+		line := scanner.Text()
+		switch {
+		case line == "":
+			t.Fatalf("%s:%d: unexpected blank line", file, lineno)
+		case line[0] == '#':
+			continue
+		case 'A' <= line[0] && line[0] <= 'Z':
+			// Test name.
+			t.Logf("%s\n", line)
+			continue
+		case line == "strings":
+			str = str[:0]
+			inStrings = true
+		case line == "regexps":
+			inStrings = false
+		case line[0] == '"':
+			q, err := strconv.Unquote(line)
+			if err != nil {
+				// Fatal because we'll get out of sync.
+				t.Fatalf("%s:%d: unquote %s: %v", file, lineno, line, err)
+			}
+			if inStrings {
+				str = append(str, q)
+				continue
+			}
+			// Is a regexp.
+			if len(input) != 0 {
+				t.Fatalf("%s:%d: out of sync: have %d strings left before %#q", file, lineno, len(input), q)
+			}
+			re, err = tryCompile(q)
+			if err != nil {
+				if err.Error() == "error parsing regexp: invalid escape sequence: `\\C`" {
+					// We don't and likely never will support \C; keep going.
+					continue
+				}
+				t.Errorf("%s:%d: compile %#q: %v", file, lineno, q, err)
+				if nfail++; nfail >= 100 {
+					t.Fatalf("stopping after %d errors", nfail)
+				}
+				continue
+			}
+			full := `\A(?:` + q + `)\z`
+			refull, err = tryCompile(full)
+			if err != nil {
+				// Fatal because q worked, so this should always work.
+				t.Fatalf("%s:%d: compile full %#q: %v", file, lineno, full, err)
+			}
+			input = str
+		case line[0] == '-' || '0' <= line[0] && line[0] <= '9':
+			// A sequence of match results.
+			ncase++
+			if re == nil {
+				// Failed to compile: skip results.
+				continue
+			}
+			if len(input) == 0 {
+				t.Fatalf("%s:%d: out of sync: no input remaining", file, lineno)
+			}
+			var text string
+			text, input = input[0], input[1:]
+			if !isSingleBytes(text) && strings.Contains(re.String(), `\B`) {
+				// RE2's \B considers every byte position,
+				// so it sees 'not word boundary' in the
+				// middle of UTF-8 sequences. This package
+				// only considers the positions between runes,
+				// so it disagrees. Skip those cases.
+				continue
+			}
+			res := strings.Split(line, ";")
+			if len(res) != len(run) {
+				t.Fatalf("%s:%d: have %d test results, want %d", file, lineno, len(res), len(run))
+			}
+			for i := range res {
+				have, suffix := run[i](re, refull, text)
+				want := parseResult(t, file, lineno, res[i])
+				if !same(have, want) {
+					t.Errorf("%s:%d: %#q%s.FindSubmatchIndex(%#q) = %v, want %v", file, lineno, re, suffix, text, have, want)
+					if nfail++; nfail >= 100 {
+						t.Fatalf("stopping after %d errors", nfail)
+					}
+					continue
+				}
+				b, suffix := match[i](re, refull, text)
+				if b != (want != nil) {
+					t.Errorf("%s:%d: %#q%s.MatchString(%#q) = %v, want %v", file, lineno, re, suffix, text, b, !b)
+					if nfail++; nfail >= 100 {
+						t.Fatalf("stopping after %d errors", nfail)
+					}
+					continue
+				}
+			}
+
+		default:
+			t.Fatalf("%s:%d: out of sync: %s\n", file, lineno, line)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		t.Fatalf("%s:%d: %v", file, lineno, err)
+	}
+	if len(input) != 0 {
+		t.Fatalf("%s:%d: out of sync: have %d strings left at EOF", file, lineno, len(input))
+	}
+	t.Logf("%d cases tested", ncase)
+}
+
+var run = []func(*Regexp, *Regexp, string) ([]int, string){
+	runFull,
+	runPartial,
+	runFullLongest,
+	runPartialLongest,
+}
+
+func runFull(re, refull *Regexp, text string) ([]int, string) {
+	refull.longest = false
+	return refull.FindStringSubmatchIndex(text), "[full]"
+}
+
+func runPartial(re, refull *Regexp, text string) ([]int, string) {
+	re.longest = false
+	return re.FindStringSubmatchIndex(text), ""
+}
+
+func runFullLongest(re, refull *Regexp, text string) ([]int, string) {
+	refull.longest = true
+	return refull.FindStringSubmatchIndex(text), "[full,longest]"
+}
+
+func runPartialLongest(re, refull *Regexp, text string) ([]int, string) {
+	re.longest = true
+	return re.FindStringSubmatchIndex(text), "[longest]"
+}
+
+var match = []func(*Regexp, *Regexp, string) (bool, string){
+	matchFull,
+	matchPartial,
+	matchFullLongest,
+	matchPartialLongest,
+}
+
+func matchFull(re, refull *Regexp, text string) (bool, string) {
+	refull.longest = false
+	return refull.MatchString(text), "[full]"
+}
+
+func matchPartial(re, refull *Regexp, text string) (bool, string) {
+	re.longest = false
+	return re.MatchString(text), ""
+}
+
+func matchFullLongest(re, refull *Regexp, text string) (bool, string) {
+	refull.longest = true
+	return refull.MatchString(text), "[full,longest]"
+}
+
+func matchPartialLongest(re, refull *Regexp, text string) (bool, string) {
+	re.longest = true
+	return re.MatchString(text), "[longest]"
+}
+
+func isSingleBytes(s string) bool {
+	for _, c := range s {
+		if c >= utf8.RuneSelf {
+			return false
+		}
+	}
+	return true
+}
+
+func tryCompile(s string) (re *Regexp, err error) {
+	// Protect against panic during Compile.
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("panic: %v", r)
+		}
+	}()
+	return Compile(s)
+}
+
+func parseResult(t *testing.T, file string, lineno int, res string) []int {
+	// A single - indicates no match.
+	if res == "-" {
+		return nil
+	}
+	// Otherwise, a space-separated list of pairs.
+	n := 1
+	for j := 0; j < len(res); j++ {
+		if res[j] == ' ' {
+			n++
+		}
+	}
+	out := make([]int, 2*n)
+	i := 0
+	n = 0
+	for j := 0; j <= len(res); j++ {
+		if j == len(res) || res[j] == ' ' {
+			// Process a single pair.  - means no submatch.
+			pair := res[i:j]
+			if pair == "-" {
+				out[n] = -1
+				out[n+1] = -1
+			} else {
+				loStr, hiStr, _ := strings.Cut(pair, "-")
+				lo, err1 := strconv.Atoi(loStr)
+				hi, err2 := strconv.Atoi(hiStr)
+				if err1 != nil || err2 != nil || lo > hi {
+					t.Fatalf("%s:%d: invalid pair %s", file, lineno, pair)
+				}
+				out[n] = lo
+				out[n+1] = hi
+			}
+			n += 2
+			i = j + 1
+		}
+	}
+	return out
+}
+
+func same(x, y []int) bool {
+	if len(x) != len(y) {
+		return false
+	}
+	for i, xi := range x {
+		if xi != y[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// TestFowler runs this package's regexp API against the
+// POSIX regular expression tests collected by Glenn Fowler
+// at http://www2.research.att.com/~astopen/testregex/testregex.html.
+func TestFowler(t *testing.T) {
+	files, err := filepath.Glob("testdata/*.dat")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, file := range files {
+		t.Log(file)
+		testFowler(t, file)
+	}
+}
+
+var notab = MustCompilePOSIX(`[^\t]+`)
+
+func testFowler(t *testing.T, file string) {
+	f, err := os.Open(file)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	defer f.Close()
+	b := bufio.NewReader(f)
+	lineno := 0
+	lastRegexp := ""
+Reading:
+	for {
+		lineno++
+		line, err := b.ReadString('\n')
+		if err != nil {
+			if err != io.EOF {
+				t.Errorf("%s:%d: %v", file, lineno, err)
+			}
+			break Reading
+		}
+
+		// http://www2.research.att.com/~astopen/man/man1/testregex.html
+		//
+		// INPUT FORMAT
+		//   Input lines may be blank, a comment beginning with #, or a test
+		//   specification. A specification is five fields separated by one
+		//   or more tabs. NULL denotes the empty string and NIL denotes the
+		//   0 pointer.
+		if line[0] == '#' || line[0] == '\n' {
+			continue Reading
+		}
+		line = line[:len(line)-1]
+		field := notab.FindAllString(line, -1)
+		for i, f := range field {
+			if f == "NULL" {
+				field[i] = ""
+			}
+			if f == "NIL" {
+				t.Logf("%s:%d: skip: %s", file, lineno, line)
+				continue Reading
+			}
+		}
+		if len(field) == 0 {
+			continue Reading
+		}
+
+		//   Field 1: the regex(3) flags to apply, one character per REG_feature
+		//   flag. The test is skipped if REG_feature is not supported by the
+		//   implementation. If the first character is not [BEASKLP] then the
+		//   specification is a global control line. One or more of [BEASKLP] may be
+		//   specified; the test will be repeated for each mode.
+		//
+		//     B 	basic			BRE	(grep, ed, sed)
+		//     E 	REG_EXTENDED		ERE	(egrep)
+		//     A	REG_AUGMENTED		ARE	(egrep with negation)
+		//     S	REG_SHELL		SRE	(sh glob)
+		//     K	REG_SHELL|REG_AUGMENTED	KRE	(ksh glob)
+		//     L	REG_LITERAL		LRE	(fgrep)
+		//
+		//     a	REG_LEFT|REG_RIGHT	implicit ^...$
+		//     b	REG_NOTBOL		lhs does not match ^
+		//     c	REG_COMMENT		ignore space and #...\n
+		//     d	REG_SHELL_DOT		explicit leading . match
+		//     e	REG_NOTEOL		rhs does not match $
+		//     f	REG_MULTIPLE		multiple \n separated patterns
+		//     g	FNM_LEADING_DIR		testfnmatch only -- match until /
+		//     h	REG_MULTIREF		multiple digit backref
+		//     i	REG_ICASE		ignore case
+		//     j	REG_SPAN		. matches \n
+		//     k	REG_ESCAPE		\ to escape [...] delimiter
+		//     l	REG_LEFT		implicit ^...
+		//     m	REG_MINIMAL		minimal match
+		//     n	REG_NEWLINE		explicit \n match
+		//     o	REG_ENCLOSED		(|&) magic inside [@|&](...)
+		//     p	REG_SHELL_PATH		explicit / match
+		//     q	REG_DELIMITED		delimited pattern
+		//     r	REG_RIGHT		implicit ...$
+		//     s	REG_SHELL_ESCAPED	\ not special
+		//     t	REG_MUSTDELIM		all delimiters must be specified
+		//     u	standard unspecified behavior -- errors not counted
+		//     v	REG_CLASS_ESCAPE	\ special inside [...]
+		//     w	REG_NOSUB		no subexpression match array
+		//     x	REG_LENIENT		let some errors slide
+		//     y	REG_LEFT		regexec() implicit ^...
+		//     z	REG_NULL		NULL subexpressions ok
+		//     $	                        expand C \c escapes in fields 2 and 3
+		//     /	                        field 2 is a regsubcomp() expression
+		//     =	                        field 3 is a regdecomp() expression
+		//
+		//   Field 1 control lines:
+		//
+		//     C		set LC_COLLATE and LC_CTYPE to locale in field 2
+		//
+		//     ?test ...	output field 5 if passed and != EXPECTED, silent otherwise
+		//     &test ...	output field 5 if current and previous passed
+		//     |test ...	output field 5 if current passed and previous failed
+		//     ; ...	output field 2 if previous failed
+		//     {test ...	skip if failed until }
+		//     }		end of skip
+		//
+		//     : comment		comment copied as output NOTE
+		//     :comment:test	:comment: ignored
+		//     N[OTE] comment	comment copied as output NOTE
+		//     T[EST] comment	comment
+		//
+		//     number		use number for nmatch (20 by default)
+		flag := field[0]
+		switch flag[0] {
+		case '?', '&', '|', ';', '{', '}':
+			// Ignore all the control operators.
+			// Just run everything.
+			flag = flag[1:]
+			if flag == "" {
+				continue Reading
+			}
+		case ':':
+			var ok bool
+			if _, flag, ok = strings.Cut(flag[1:], ":"); !ok {
+				t.Logf("skip: %s", line)
+				continue Reading
+			}
+		case 'C', 'N', 'T', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			t.Logf("skip: %s", line)
+			continue Reading
+		}
+
+		// Can check field count now that we've handled the myriad comment formats.
+		if len(field) < 4 {
+			t.Errorf("%s:%d: too few fields: %s", file, lineno, line)
+			continue Reading
+		}
+
+		// Expand C escapes (a.k.a. Go escapes).
+		if strings.Contains(flag, "$") {
+			f := `"` + field[1] + `"`
+			if field[1], err = strconv.Unquote(f); err != nil {
+				t.Errorf("%s:%d: cannot unquote %s", file, lineno, f)
+			}
+			f = `"` + field[2] + `"`
+			if field[2], err = strconv.Unquote(f); err != nil {
+				t.Errorf("%s:%d: cannot unquote %s", file, lineno, f)
+			}
+		}
+
+		//   Field 2: the regular expression pattern; SAME uses the pattern from
+		//     the previous specification.
+		//
+		if field[1] == "SAME" {
+			field[1] = lastRegexp
+		}
+		lastRegexp = field[1]
+
+		//   Field 3: the string to match.
+		text := field[2]
+
+		//   Field 4: the test outcome...
+		ok, shouldCompile, shouldMatch, pos := parseFowlerResult(field[3])
+		if !ok {
+			t.Errorf("%s:%d: cannot parse result %#q", file, lineno, field[3])
+			continue Reading
+		}
+
+		//   Field 5: optional comment appended to the report.
+
+	Testing:
+		// Run test once for each specified capital letter mode that we support.
+		for _, c := range flag {
+			pattern := field[1]
+			syn := syntax.POSIX | syntax.ClassNL
+			switch c {
+			default:
+				continue Testing
+			case 'E':
+				// extended regexp (what we support)
+			case 'L':
+				// literal
+				pattern = QuoteMeta(pattern)
+			}
+
+			for _, c := range flag {
+				switch c {
+				case 'i':
+					syn |= syntax.FoldCase
+				}
+			}
+
+			re, err := compile(pattern, syn, true)
+			if err != nil {
+				if shouldCompile {
+					t.Errorf("%s:%d: %#q did not compile", file, lineno, pattern)
+				}
+				continue Testing
+			}
+			if !shouldCompile {
+				t.Errorf("%s:%d: %#q should not compile", file, lineno, pattern)
+				continue Testing
+			}
+			match := re.MatchString(text)
+			if match != shouldMatch {
+				t.Errorf("%s:%d: %#q.Match(%#q) = %v, want %v", file, lineno, pattern, text, match, shouldMatch)
+				continue Testing
+			}
+			have := re.FindStringSubmatchIndex(text)
+			if (len(have) > 0) != match {
+				t.Errorf("%s:%d: %#q.Match(%#q) = %v, but %#q.FindSubmatchIndex(%#q) = %v", file, lineno, pattern, text, match, pattern, text, have)
+				continue Testing
+			}
+			if len(have) > len(pos) {
+				have = have[:len(pos)]
+			}
+			if !same(have, pos) {
+				t.Errorf("%s:%d: %#q.FindSubmatchIndex(%#q) = %v, want %v", file, lineno, pattern, text, have, pos)
+			}
+		}
+	}
+}
+
+func parseFowlerResult(s string) (ok, compiled, matched bool, pos []int) {
+	//   Field 4: the test outcome. This is either one of the posix error
+	//     codes (with REG_ omitted) or the match array, a list of (m,n)
+	//     entries with m and n being first and last+1 positions in the
+	//     field 3 string, or NULL if REG_NOSUB is in effect and success
+	//     is expected. BADPAT is acceptable in place of any regcomp(3)
+	//     error code. The match[] array is initialized to (-2,-2) before
+	//     each test. All array elements from 0 to nmatch-1 must be specified
+	//     in the outcome. Unspecified endpoints (offset -1) are denoted by ?.
+	//     Unset endpoints (offset -2) are denoted by X. {x}(o:n) denotes a
+	//     matched (?{...}) expression, where x is the text enclosed by {...},
+	//     o is the expression ordinal counting from 1, and n is the length of
+	//     the unmatched portion of the subject string. If x starts with a
+	//     number then that is the return value of re_execf(), otherwise 0 is
+	//     returned.
+	switch {
+	case s == "":
+		// Match with no position information.
+		ok = true
+		compiled = true
+		matched = true
+		return
+	case s == "NOMATCH":
+		// Match failure.
+		ok = true
+		compiled = true
+		matched = false
+		return
+	case 'A' <= s[0] && s[0] <= 'Z':
+		// All the other error codes are compile errors.
+		ok = true
+		compiled = false
+		return
+	}
+	compiled = true
+
+	var x []int
+	for s != "" {
+		var end byte = ')'
+		if len(x)%2 == 0 {
+			if s[0] != '(' {
+				ok = false
+				return
+			}
+			s = s[1:]
+			end = ','
+		}
+		i := 0
+		for i < len(s) && s[i] != end {
+			i++
+		}
+		if i == 0 || i == len(s) {
+			ok = false
+			return
+		}
+		var v = -1
+		var err error
+		if s[:i] != "?" {
+			v, err = strconv.Atoi(s[:i])
+			if err != nil {
+				ok = false
+				return
+			}
+		}
+		x = append(x, v)
+		s = s[i+1:]
+	}
+	if len(x)%2 != 0 {
+		ok = false
+		return
+	}
+	ok = true
+	matched = true
+	pos = x
+	return
+}
+
+var text []byte
+
+func makeText(n int) []byte {
+	if len(text) >= n {
+		return text[:n]
+	}
+	text = make([]byte, n)
+	x := ^uint32(0)
+	for i := range text {
+		x += x
+		x ^= 1
+		if int32(x) < 0 {
+			x ^= 0x88888eef
+		}
+		if x%31 == 0 {
+			text[i] = '\n'
+		} else {
+			text[i] = byte(x%(0x7E+1-0x20) + 0x20)
+		}
+	}
+	return text
+}
+
+func BenchmarkMatch(b *testing.B) {
+	isRaceBuilder := strings.HasSuffix(testenv.Builder(), "-race")
+
+	for _, data := range benchData {
+		r := MustCompile(data.re)
+		for _, size := range benchSizes {
+			if (isRaceBuilder || testing.Short()) && size.n > 1<<10 {
+				continue
+			}
+			t := makeText(size.n)
+			b.Run(data.name+"/"+size.name, func(b *testing.B) {
+				b.SetBytes(int64(size.n))
+				for i := 0; i < b.N; i++ {
+					if r.Match(t) {
+						b.Fatal("match!")
+					}
+				}
+			})
+		}
+	}
+}
+
+func BenchmarkMatch_onepass_regex(b *testing.B) {
+	isRaceBuilder := strings.HasSuffix(testenv.Builder(), "-race")
+	r := MustCompile(`(?s)\A.*\z`)
+	if r.onepass == nil {
+		b.Fatalf("want onepass regex, but %q is not onepass", r)
+	}
+	for _, size := range benchSizes {
+		if (isRaceBuilder || testing.Short()) && size.n > 1<<10 {
+			continue
+		}
+		t := makeText(size.n)
+		b.Run(size.name, func(b *testing.B) {
+			b.SetBytes(int64(size.n))
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				if !r.Match(t) {
+					b.Fatal("not match!")
+				}
+			}
+		})
+	}
+}
+
+var benchData = []struct{ name, re string }{
+	{"Easy0", "ABCDEFGHIJKLMNOPQRSTUVWXYZ$"},
+	{"Easy0i", "(?i)ABCDEFGHIJklmnopqrstuvwxyz$"},
+	{"Easy1", "A[AB]B[BC]C[CD]D[DE]E[EF]F[FG]G[GH]H[HI]I[IJ]J$"},
+	{"Medium", "[XYZ]ABCDEFGHIJKLMNOPQRSTUVWXYZ$"},
+	{"Hard", "[ -~]*ABCDEFGHIJKLMNOPQRSTUVWXYZ$"},
+	{"Hard1", "ABCD|CDEF|EFGH|GHIJ|IJKL|KLMN|MNOP|OPQR|QRST|STUV|UVWX|WXYZ"},
+}
+
+var benchSizes = []struct {
+	name string
+	n    int
+}{
+	{"16", 16},
+	{"32", 32},
+	{"1K", 1 << 10},
+	{"32K", 32 << 10},
+	{"1M", 1 << 20},
+	{"32M", 32 << 20},
+}
+
+func TestLongest(t *testing.T) {
+	re, err := Compile(`a(|b)`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, w := re.FindString("ab"), "a"; g != w {
+		t.Errorf("first match was %q, want %q", g, w)
+	}
+	re.Longest()
+	if g, w := re.FindString("ab"), "ab"; g != w {
+		t.Errorf("longest match was %q, want %q", g, w)
+	}
+}
+
+// TestProgramTooLongForBacktrack tests that a regex which is too long
+// for the backtracker still executes properly.
+func TestProgramTooLongForBacktrack(t *testing.T) {
+	longRegex := MustCompile(`(one|two|three|four|five|six|seven|eight|nine|ten|eleven|twelve|thirteen|fourteen|fifteen|sixteen|seventeen|eighteen|nineteen|twenty|twentyone|twentytwo|twentythree|twentyfour|twentyfive|twentysix|twentyseven|twentyeight|twentynine|thirty|thirtyone|thirtytwo|thirtythree|thirtyfour|thirtyfive|thirtysix|thirtyseven|thirtyeight|thirtynine|forty|fortyone|fortytwo|fortythree|fortyfour|fortyfive|fortysix|fortyseven|fortyeight|fortynine|fifty|fiftyone|fiftytwo|fiftythree|fiftyfour|fiftyfive|fiftysix|fiftyseven|fiftyeight|fiftynine|sixty|sixtyone|sixtytwo|sixtythree|sixtyfour|sixtyfive|sixtysix|sixtyseven|sixtyeight|sixtynine|seventy|seventyone|seventytwo|seventythree|seventyfour|seventyfive|seventysix|seventyseven|seventyeight|seventynine|eighty|eightyone|eightytwo|eightythree|eightyfour|eightyfive|eightysix|eightyseven|eightyeight|eightynine|ninety|ninetyone|ninetytwo|ninetythree|ninetyfour|ninetyfive|ninetysix|ninetyseven|ninetyeight|ninetynine|onehundred)`)
+	if !longRegex.MatchString("two") {
+		t.Errorf("longRegex.MatchString(\"two\") was false, want true")
+	}
+	if longRegex.MatchString("xxx") {
+		t.Errorf("longRegex.MatchString(\"xxx\") was true, want false")
+	}
+}