libregex: Implement a subset of the GNU extensions

The entire patch-set is not yet mature enough for commit, but this usable
subset is generally enough for googletest to be happy with and mostly map to
some existing concepts, so they're not as invasive.

The specific changes included here are:

- Branching in BREs with \|
- \w and \W for [[:alnum:]] and [^[:alnum:]] respectively
- \s and \S for [[:space:]] and [^[:space:]] respectively
- Additional quantifiers in BREs, \? and \+ (self-explanatory)

There's some #ifdef'd out work for allowing empty branches as a match-all.
This is a feature that's under assessment... future work will determine
how standard this behavior is and act accordingly.

lib/libc/regex/regcomp.c

@@ -92,6 +92,7 @@ struct parse {
 	const char *next;	/* next character in RE */
 	const char *end;	/* end of string (-> NUL normally) */
 	int error;		/* has an error been seen? */
+	int gnuext;
 	sop *strip;		/* malloced strip */
 	sopno ssize;		/* malloced strip size (allocated) */
 	sopno slen;		/* malloced strip length (used) */
@@ -131,7 +132,9 @@ static int p_count(struct parse *p);
 static void p_bracket(struct parse *p);
 static int p_range_cmp(wchar_t c1, wchar_t c2);
 static void p_b_term(struct parse *p, cset *cs);
+static int p_b_pseudoclass(struct parse *p, char c);
 static void p_b_cclass(struct parse *p, cset *cs);
+static void p_b_cclass_named(struct parse *p, cset *cs, const char[]);
 static void p_b_eclass(struct parse *p, cset *cs);
 static wint_t p_b_symbol(struct parse *p);
 static wint_t p_b_coll_elem(struct parse *p, wint_t endc);
@@ -181,6 +184,7 @@ static char nuls[10];		/* place to point scanner in event of error */
 #define	SEESPEC(a)	(p->bre ? SEETWO('\\', a) : SEE(a))
 #define	EAT(c)	((SEE(c)) ? (NEXT(), 1) : 0)
 #define	EATTWO(a, b)	((SEETWO(a, b)) ? (NEXT2(), 1) : 0)
+#define	EATSPEC(a)	(p->bre ? EATTWO('\\', a) : EAT(a))
 #define	NEXT()	(p->next++)
 #define	NEXT2()	(p->next += 2)
 #define	NEXTn(n)	(p->next += (n))
@@ -270,14 +274,22 @@ regcomp_internal(regex_t * __restrict preg,
 		p->pbegin[i] = 0;
 		p->pend[i] = 0;
 	}
+#ifdef LIBREGEX
+	if (cflags&REG_POSIX) {
+		p->gnuext = false;
+		p->allowbranch = (cflags & REG_EXTENDED) != 0;
+	} else
+		p->gnuext = p->allowbranch = true;
+#else
+	p->gnuext = false;
+	p->allowbranch = (cflags & REG_EXTENDED) != 0;
+#endif
 	if (cflags & REG_EXTENDED) {
-		p->allowbranch = true;
 		p->bre = false;
 		p->parse_expr = p_ere_exp;
 		p->pre_parse = NULL;
 		p->post_parse = NULL;
 	} else {
-		p->allowbranch = false;
 		p->bre = true;
 		p->parse_expr = p_simp_re;
 		p->pre_parse = p_bre_pre_parse;
@@ -388,6 +400,10 @@ p_ere_exp(struct parse *p, struct branchc *bc)
 	sopno pos;
 	int count;
 	int count2;
+#ifdef LIBREGEX
+	int i;
+	int handled;
+#endif
 	sopno subno;
 	int wascaret = 0;
 
@@ -395,6 +411,9 @@ p_ere_exp(struct parse *p, struct branchc *bc)
 	assert(MORE());		/* caller should have ensured this */
 	c = GETNEXT();
 
+#ifdef LIBREGEX
+	handled = 0;
+#endif
 	pos = HERE();
 	switch (c) {
 	case '(':
@@ -457,6 +476,47 @@ p_ere_exp(struct parse *p, struct branchc *bc)
 	case '\\':
 		(void)REQUIRE(MORE(), REG_EESCAPE);
 		wc = WGETNEXT();
+#ifdef LIBREGEX
+		if (p->gnuext) {
+			handled = 1;
+			switch (wc) {
+			case 'W':
+			case 'w':
+			case 'S':
+			case 's':
+				p_b_pseudoclass(p, wc);
+				break;
+			case '1':
+			case '2':
+			case '3':
+			case '4':
+			case '5':
+			case '6':
+			case '7':
+			case '8':
+			case '9':
+				i = wc - '0';
+				assert(i < NPAREN);
+				if (p->pend[i] != 0) {
+					assert(i <= p->g->nsub);
+					EMIT(OBACK_, i);
+					assert(p->pbegin[i] != 0);
+					assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
+					assert(OP(p->strip[p->pend[i]]) == ORPAREN);
+					(void) dupl(p, p->pbegin[i]+1, p->pend[i]);
+					EMIT(O_BACK, i);
+				} else
+					SETERROR(REG_ESUBREG);
+				p->g->backrefs = 1;
+				break;
+			default:
+				handled = 0;
+			}
+			/* Don't proceed to the POSIX bits if we've already handled it */
+			if (handled)
+				break;
+		}
+#endif
 		switch (wc) {
 		case '<':
 			EMIT(OBOW, 0);
@@ -567,7 +627,7 @@ p_branch_eat_delim(struct parse *p, struct branchc *bc)
 
 	(void)bc;
 	nskip = 0;
-	while (EAT('|'))
+	while (EATSPEC('|'))
 		++nskip;
 	return (nskip);
 }
@@ -619,9 +679,15 @@ static bool
 p_branch_empty(struct parse *p, struct branchc *bc)
 {
 
+#if defined(LIBREGEX) && defined(NOTYET)
+	if (bc->outer)
+		p->g->iflags |= EMPTBR;
+	return (true);
+#else
 	(void)bc;
 	SETERROR(REG_EMPTY);
 	return (false);
+#endif
 }
 
 /*
@@ -713,7 +779,11 @@ p_re(struct parse *p,
 		}
 		if (p->post_parse != NULL)
 			p->post_parse(p, &bc);
-		(void) REQUIRE(HERE() != bc.start, REG_EMPTY);
+		(void) REQUIRE(p->gnuext || HERE() != bc.start, REG_EMPTY);
+#ifdef LIBREGEX
+		if (HERE() == bc.start && !p_branch_empty(p, &bc))
+			break;
+#endif
 		if (!p->allowbranch)
 			break;
 		/*
@@ -740,101 +810,122 @@ static bool			/* was the simple RE an unbackslashed $? */
 p_simp_re(struct parse *p, struct branchc *bc)
 {
 	int c;
+	int cc;			/* convenient/control character */
 	int count;
 	int count2;
 	sopno pos;
+	bool handled;
 	int i;
 	wint_t wc;
 	sopno subno;
 #	define	BACKSL	(1<<CHAR_BIT)
 
 	pos = HERE();		/* repetition op, if any, covers from here */
+	handled = false;
 
 	assert(MORE());		/* caller should have ensured this */
 	c = GETNEXT();
 	if (c == '\\') {
 		(void)REQUIRE(MORE(), REG_EESCAPE);
-		c = BACKSL | GETNEXT();
-	}
-	switch (c) {
-	case '.':
-		if (p->g->cflags&REG_NEWLINE)
-			nonnewline(p);
-		else
-			EMIT(OANY, 0);
-		break;
-	case '[':
-		p_bracket(p);
-		break;
-	case BACKSL|'<':
-		EMIT(OBOW, 0);
-		break;
-	case BACKSL|'>':
-		EMIT(OEOW, 0);
-		break;
-	case BACKSL|'{':
-		SETERROR(REG_BADRPT);
-		break;
-	case BACKSL|'(':
-		p->g->nsub++;
-		subno = p->g->nsub;
-		if (subno < NPAREN)
-			p->pbegin[subno] = HERE();
-		EMIT(OLPAREN, subno);
-		/* the MORE here is an error heuristic */
-		if (MORE() && !SEETWO('\\', ')'))
-			p_re(p, '\\', ')');
-		if (subno < NPAREN) {
-			p->pend[subno] = HERE();
-			assert(p->pend[subno] != 0);
+		cc = GETNEXT();
+		c = BACKSL | cc;
+#ifdef LIBREGEX
+		if (p->gnuext) {
+			handled = true;
+			switch (c) {
+			case BACKSL|'W':
+			case BACKSL|'w':
+			case BACKSL|'S':
+			case BACKSL|'s':
+				p_b_pseudoclass(p, cc);
+				break;
+			default:
+				handled = false;
+			}
+		}
+#endif
+	}
+	if (!handled) {
+		switch (c) {
+		case '.':
+			if (p->g->cflags&REG_NEWLINE)
+				nonnewline(p);
+			else
+				EMIT(OANY, 0);
+			break;
+		case '[':
+			p_bracket(p);
+			break;
+		case BACKSL|'<':
+			EMIT(OBOW, 0);
+			break;
+		case BACKSL|'>':
+			EMIT(OEOW, 0);
+			break;
+		case BACKSL|'{':
+			SETERROR(REG_BADRPT);
+			break;
+		case BACKSL|'(':
+			p->g->nsub++;
+			subno = p->g->nsub;
+			if (subno < NPAREN)
+				p->pbegin[subno] = HERE();
+			EMIT(OLPAREN, subno);
+			/* the MORE here is an error heuristic */
+			if (MORE() && !SEETWO('\\', ')'))
+				p_re(p, '\\', ')');
+			if (subno < NPAREN) {
+				p->pend[subno] = HERE();
+				assert(p->pend[subno] != 0);
+			}
+			EMIT(ORPAREN, subno);
+			(void)REQUIRE(EATTWO('\\', ')'), REG_EPAREN);
+			break;
+		case BACKSL|')':	/* should not get here -- must be user */
+			SETERROR(REG_EPAREN);
+			break;
+		case BACKSL|'1':
+		case BACKSL|'2':
+		case BACKSL|'3':
+		case BACKSL|'4':
+		case BACKSL|'5':
+		case BACKSL|'6':
+		case BACKSL|'7':
+		case BACKSL|'8':
+		case BACKSL|'9':
+			i = (c&~BACKSL) - '0';
+			assert(i < NPAREN);
+			if (p->pend[i] != 0) {
+				assert(i <= p->g->nsub);
+				EMIT(OBACK_, i);
+				assert(p->pbegin[i] != 0);
+				assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
+				assert(OP(p->strip[p->pend[i]]) == ORPAREN);
+				(void) dupl(p, p->pbegin[i]+1, p->pend[i]);
+				EMIT(O_BACK, i);
+			} else
+				SETERROR(REG_ESUBREG);
+			p->g->backrefs = 1;
+			break;
+		case '*':
+			/*
+			 * Ordinary if used as the first character beyond BOL anchor of
+			 * a (sub-)expression, counts as a bad repetition operator if it
+			 * appears otherwise.
+			 */
+			(void)REQUIRE(bc->nchain == 0, REG_BADRPT);
+			/* FALLTHROUGH */
+		default:
+			if (p->error != 0)
+				return (false);	/* Definitely not $... */
+			p->next--;
+			wc = WGETNEXT();
+			if ((c & BACKSL) == 0 || may_escape(p, wc))
+				ordinary(p, wc);
+			else
+				SETERROR(REG_EESCAPE);
+			break;
 		}
-		EMIT(ORPAREN, subno);
-		(void)REQUIRE(EATTWO('\\', ')'), REG_EPAREN);
-		break;
-	case BACKSL|')':	/* should not get here -- must be user */
-		SETERROR(REG_EPAREN);
-		break;
-	case BACKSL|'1':
-	case BACKSL|'2':
-	case BACKSL|'3':
-	case BACKSL|'4':
-	case BACKSL|'5':
-	case BACKSL|'6':
-	case BACKSL|'7':
-	case BACKSL|'8':
-	case BACKSL|'9':
-		i = (c&~BACKSL) - '0';
-		assert(i < NPAREN);
-		if (p->pend[i] != 0) {
-			assert(i <= p->g->nsub);
-			EMIT(OBACK_, i);
-			assert(p->pbegin[i] != 0);
-			assert(OP(p->strip[p->pbegin[i]]) == OLPAREN);
-			assert(OP(p->strip[p->pend[i]]) == ORPAREN);
-			(void) dupl(p, p->pbegin[i]+1, p->pend[i]);
-			EMIT(O_BACK, i);
-		} else
-			SETERROR(REG_ESUBREG);
-		p->g->backrefs = 1;
-		break;
-	case '*':
-		/*
-		 * Ordinary if used as the first character beyond BOL anchor of
-		 * a (sub-)expression, counts as a bad repetition operator if it
-		 * appears otherwise.
-		 */
-		(void)REQUIRE(bc->nchain == 0, REG_BADRPT);
-		/* FALLTHROUGH */
-	default:
-		if (p->error != 0)
-			return (false);	/* Definitely not $... */
-		p->next--;
-		wc = WGETNEXT();
-		if ((c & BACKSL) == 0 || may_escape(p, wc))
-			ordinary(p, wc);
-		else
-			SETERROR(REG_EESCAPE);
-		break;
 	}
 
 	if (EAT('*')) {		/* implemented as +? */
@@ -843,6 +934,14 @@ p_simp_re(struct parse *p, struct branchc *bc)
 		ASTERN(O_PLUS, pos);
 		INSERT(OQUEST_, pos);
 		ASTERN(O_QUEST, pos);
+#ifdef LIBREGEX
+	} else if (p->gnuext && EATTWO('\\', '?')) {
+		INSERT(OQUEST_, pos);
+		ASTERN(O_QUEST, pos);
+	} else if (p->gnuext && EATTWO('\\', '+')) {
+		INSERT(OPLUS_, pos);
+		ASTERN(O_PLUS, pos);
+#endif
 	} else if (EATTWO('\\', '{')) {
 		count = p_count(p);
 		if (EAT(',')) {
@@ -1034,6 +1133,41 @@ p_b_term(struct parse *p, cset *cs)
 	}
 }
 
+/*
+ - p_b_pseudoclass - parse a pseudo-class (\w, \W, \s, \S)
+ == static int p_b_pseudoclass(struct parse *p, char c)
+ */
+static int
+p_b_pseudoclass(struct parse *p, char c) {
+	cset *cs;
+
+	if ((cs = allocset(p)) == NULL)
+		return(0);
+
+	if (p->g->cflags&REG_ICASE)
+		cs->icase = 1;
+
+	switch (c) {
+	case 'W':
+		cs->invert = 1;
+		/* PASSTHROUGH */
+	case 'w':
+		p_b_cclass_named(p, cs, "alnum");
+		break;
+	case 'S':
+		cs->invert = 1;
+		/* PASSTHROUGH */
+	case 's':
+		p_b_cclass_named(p, cs, "space");
+		break;
+	default:
+		return(0);
+	}
+
+	EMIT(OANYOF, (int)(cs - p->g->sets));
+	return(1);
+}
+
 /*
  - p_b_cclass - parse a character-class name and deal with it
  == static void p_b_cclass(struct parse *p, cset *cs);
@@ -1043,7 +1177,6 @@ p_b_cclass(struct parse *p, cset *cs)
 {
 	const char *sp = p->next;
 	size_t len;
-	wctype_t wct;
 	char clname[16];
 
 	while (MORE() && isalpha((uch)PEEK()))
@@ -1055,6 +1188,17 @@ p_b_cclass(struct parse *p, cset *cs)
 	}
 	memcpy(clname, sp, len);
 	clname[len] = '\0';
+
+	p_b_cclass_named(p, cs, clname);
+}
+/*
+ - p_b_cclass_named - deal with a named character class
+ == static void p_b_cclass_named(struct parse *p, cset *cs, const char []);
+ */
+static void
+p_b_cclass_named(struct parse *p, cset *cs, const char clname[]) {
+	wctype_t wct;
+
 	if ((wct = wctype(clname)) == 0) {
 		SETERROR(REG_ECTYPE);
 		return;

lib/libc/regex/regex2.h

@@ -182,6 +182,7 @@ struct re_guts {
 #		define	USEBOL	01	/* used ^ */
 #		define	USEEOL	02	/* used $ */
 #		define	BAD	04	/* something wrong */
+#		define	EMPTBR	010	/* empty branch present */
 	int nbol;		/* number of ^ used */
 	int neol;		/* number of $ used */
 	char *must;		/* match must contain this string */