diff --git a/lib/libc/regex/engine.c b/lib/libc/regex/engine.c
index da87a16f6f2c..a44511b8d561 100644
--- a/lib/libc/regex/engine.c
+++ b/lib/libc/regex/engine.c
@@ -82,11 +82,11 @@ struct match {
 	struct re_guts *g;
 	int eflags;
 	regmatch_t *pmatch;	/* [nsub+1] (0 element unused) */
-	char *offp;		/* offsets work from here */
-	char *beginp;		/* start of string -- virtual NUL precedes */
-	char *endp;		/* end of string -- virtual NUL here */
-	char *coldp;		/* can be no match starting before here */
-	char **lastpos;		/* [nplus+1] */
+	const char *offp;	/* offsets work from here */
+	const char *beginp;	/* start of string -- virtual NUL precedes */
+	const char *endp;	/* end of string -- virtual NUL here */
+	const char *coldp;	/* can be no match starting before here */
+	const char **lastpos;	/* [nplus+1] */
 	STATEVARS;
 	states st;		/* current states */
 	states fresh;		/* states for a fresh start */
@@ -101,11 +101,11 @@ extern "C" {
 #endif
 
 /* === engine.c === */
-static int matcher(struct re_guts *g, char *string, size_t nmatch, regmatch_t pmatch[], int eflags);
-static char *dissect(struct match *m, char *start, char *stop, sopno startst, sopno stopst);
-static char *backref(struct match *m, char *start, char *stop, sopno startst, sopno stopst, sopno lev, int);
-static char *fast(struct match *m, char *start, char *stop, sopno startst, sopno stopst);
-static char *slow(struct match *m, char *start, char *stop, sopno startst, sopno stopst);
+static int matcher(struct re_guts *g, const char *string, size_t nmatch, regmatch_t pmatch[], int eflags);
+static const char *dissect(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
+static const char *backref(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst, sopno lev, int);
+static const char *fast(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
+static const char *slow(struct match *m, const char *start, const char *stop, sopno startst, sopno stopst);
 static states step(struct re_guts *g, sopno start, sopno stop, states bef, wint_t ch, states aft);
 #define MAX_RECURSION	100
 #define	BOL	(OUT-1)
@@ -117,13 +117,13 @@ static states step(struct re_guts *g, sopno start, sopno stop, states bef, wint_
 #define	BADCHAR	(BOL-6)
 #define	NONCHAR(c)	((c) <= OUT)
 #ifdef REDEBUG
-static void print(struct match *m, char *caption, states st, int ch, FILE *d);
+static void print(struct match *m, const char *caption, states st, int ch, FILE *d);
 #endif
 #ifdef REDEBUG
-static void at(struct match *m, char *title, char *start, char *stop, sopno startst, sopno stopst);
+static void at(struct match *m, const char *title, const char *start, const char *stop, sopno startst, sopno stopst);
 #endif
 #ifdef REDEBUG
-static char *pchar(int ch);
+static const char *pchar(int ch);
 #endif
 
 #ifdef __cplusplus
@@ -143,31 +143,30 @@ static char *pchar(int ch);
 
 /*
  - matcher - the actual matching engine
- == static int matcher(struct re_guts *g, char *string, \
+ == static int matcher(struct re_guts *g, const char *string, \
  ==	size_t nmatch, regmatch_t pmatch[], int eflags);
  */
 static int			/* 0 success, REG_NOMATCH failure */
-matcher(g, string, nmatch, pmatch, eflags)
-struct re_guts *g;
-char *string;
-size_t nmatch;
-regmatch_t pmatch[];
-int eflags;
+matcher(struct re_guts *g,
+	const char *string,
+	size_t nmatch,
+	regmatch_t pmatch[],
+	int eflags)
 {
-	char *endp;
+	const char *endp;
 	int i;
 	struct match mv;
 	struct match *m = &mv;
-	char *dp;
+	const char *dp;
 	const sopno gf = g->firststate+1;	/* +1 for OEND */
 	const sopno gl = g->laststate;
-	char *start;
-	char *stop;
+	const char *start;
+	const char *stop;
 	/* Boyer-Moore algorithms variables */
-	char *pp;
+	const char *pp;
 	int cj, mj;
-	char *mustfirst;
-	char *mustlast;
+	const char *mustfirst;
+	const char *mustlast;
 	int *matchjump;
 	int *charjump;
 
@@ -291,8 +290,8 @@ int eflags;
 			dp = dissect(m, m->coldp, endp, gf, gl);
 		} else {
 			if (g->nplus > 0 && m->lastpos == NULL)
-				m->lastpos = (char **)malloc((g->nplus+1) *
-							sizeof(char *));
+				m->lastpos = malloc((g->nplus+1) *
+						sizeof(const char *));
 			if (g->nplus > 0 && m->lastpos == NULL) {
 				free(m->pmatch);
 				STATETEARDOWN(m);
@@ -362,30 +361,29 @@ int eflags;
 
 /*
  - dissect - figure out what matched what, no back references
- == static char *dissect(struct match *m, char *start, \
- ==	char *stop, sopno startst, sopno stopst);
+ == static const char *dissect(struct match *m, const char *start, \
+ ==	const char *stop, sopno startst, sopno stopst);
  */
-static char *			/* == stop (success) always */
-dissect(m, start, stop, startst, stopst)
-struct match *m;
-char *start;
-char *stop;
-sopno startst;
-sopno stopst;
+static const char *		/* == stop (success) always */
+dissect(struct match *m,
+	const char *start,
+	const char *stop,
+	sopno startst,
+	sopno stopst)
 {
 	int i;
 	sopno ss;		/* start sop of current subRE */
 	sopno es;		/* end sop of current subRE */
-	char *sp;		/* start of string matched by it */
-	char *stp;		/* string matched by it cannot pass here */
-	char *rest;		/* start of rest of string */
-	char *tail;		/* string unmatched by rest of RE */
+	const char *sp;		/* start of string matched by it */
+	const char *stp;	/* string matched by it cannot pass here */
+	const char *rest;	/* start of rest of string */
+	const char *tail;	/* string unmatched by rest of RE */
 	sopno ssub;		/* start sop of subsubRE */
 	sopno esub;		/* end sop of subsubRE */
-	char *ssp;		/* start of string matched by subsubRE */
-	char *sep;		/* end of string matched by subsubRE */
-	char *oldssp;		/* previous ssp */
-	char *dp;
+	const char *ssp;	/* start of string matched by subsubRE */
+	const char *sep;	/* end of string matched by subsubRE */
+	const char *oldssp;	/* previous ssp */
+	const char *dp;
 
 	AT("diss", start, stop, startst, stopst);
 	sp = start;
@@ -550,26 +548,25 @@ sopno stopst;
 
 /*
  - backref - figure out what matched what, figuring in back references
- == static char *backref(struct match *m, char *start, \
- ==	char *stop, sopno startst, sopno stopst, sopno lev);
+ == static const char *backref(struct match *m, const char *start, \
+ ==	const char *stop, sopno startst, sopno stopst, sopno lev);
  */
-static char *			/* == stop (success) or NULL (failure) */
-backref(m, start, stop, startst, stopst, lev, rec)
-struct match *m;
-char *start;
-char *stop;
-sopno startst;
-sopno stopst;
-sopno lev;			/* PLUS nesting level */
-int rec;
+static const char *		/* == stop (success) or NULL (failure) */
+backref(struct match *m,
+	const char *start,
+	const char *stop,
+	sopno startst,
+	sopno stopst,
+	sopno lev,		/* PLUS nesting level */
+	int rec)
 {
 	int i;
 	sopno ss;		/* start sop of current subRE */
-	char *sp;		/* start of string matched by it */
+	const char *sp;		/* start of string matched by it */
 	sopno ssub;		/* start sop of subsubRE */
 	sopno esub;		/* end sop of subsubRE */
-	char *ssp;		/* start of string matched by subsubRE */
-	char *dp;
+	const char *ssp;	/* start of string matched by subsubRE */
+	const char *dp;
 	size_t len;
 	int hard;
 	sop s;
@@ -767,26 +764,25 @@ int rec;
 
 /*
  - fast - step through the string at top speed
- == static char *fast(struct match *m, char *start, \
- ==	char *stop, sopno startst, sopno stopst);
+ == static const char *fast(struct match *m, const char *start, \
+ ==	const char *stop, sopno startst, sopno stopst);
  */
-static char *			/* where tentative match ended, or NULL */
-fast(m, start, stop, startst, stopst)
-struct match *m;
-char *start;
-char *stop;
-sopno startst;
-sopno stopst;
+static const char *		/* where tentative match ended, or NULL */
+fast(	struct match *m,
+	const char *start,
+	const char *stop,
+	sopno startst,
+	sopno stopst)
 {
 	states st = m->st;
 	states fresh = m->fresh;
 	states tmp = m->tmp;
-	char *p = start;
+	const char *p = start;
 	wint_t c;
 	wint_t lastc;		/* previous c */
 	wint_t flagch;
 	int i;
-	char *coldp;		/* last p after which no match was underway */
+	const char *coldp;	/* last p after which no match was underway */
 	size_t clen;
 
 	CLEAR(st);
@@ -873,26 +869,25 @@ sopno stopst;
 
 /*
  - slow - step through the string more deliberately
- == static char *slow(struct match *m, char *start, \
- ==	char *stop, sopno startst, sopno stopst);
+ == static const char *slow(struct match *m, const char *start, \
+ ==	const char *stop, sopno startst, sopno stopst);
  */
-static char *			/* where it ended */
-slow(m, start, stop, startst, stopst)
-struct match *m;
-char *start;
-char *stop;
-sopno startst;
-sopno stopst;
+static const char *		/* where it ended */
+slow(	struct match *m,
+	const char *start,
+	const char *stop,
+	sopno startst,
+	sopno stopst)
 {
 	states st = m->st;
 	states empty = m->empty;
 	states tmp = m->tmp;
-	char *p = start;
+	const char *p = start;
 	wint_t c;
 	wint_t lastc;		/* previous c */
 	wint_t flagch;
 	int i;
-	char *matchp;		/* last p at which a match ended */
+	const char *matchp;	/* last p at which a match ended */
 	size_t clen;
 
 	AT("slow", start, stop, startst, stopst);
@@ -987,13 +982,12 @@ sopno stopst;
  == #define	NONCHAR(c)	((c) <= OUT)
  */
 static states
-step(g, start, stop, bef, ch, aft)
-struct re_guts *g;
-sopno start;			/* start state within strip */
-sopno stop;			/* state after stop state within strip */
-states bef;			/* states reachable before */
-wint_t ch;			/* character or NONCHAR code */
-states aft;			/* states already known reachable after */
+step(struct re_guts *g,
+	sopno start,		/* start state within strip */
+	sopno stop,		/* state after stop state within strip */
+	states bef,		/* states reachable before */
+	wint_t ch,		/* character or NONCHAR code */
+	states aft)		/* states already known reachable after */
 {
 	cset *cs;
 	sop s;
@@ -1104,17 +1098,16 @@ states aft;			/* states already known reachable after */
 /*
  - print - print a set of states
  == #ifdef REDEBUG
- == static void print(struct match *m, char *caption, states st, \
+ == static void print(struct match *m, const char *caption, states st, \
  ==	int ch, FILE *d);
  == #endif
  */
 static void
-print(m, caption, st, ch, d)
-struct match *m;
-char *caption;
-states st;
-int ch;
-FILE *d;
+print(struct match *m,
+	const char *caption,
+	states st,
+	int ch,
+	FILE *d)
 {
 	struct re_guts *g = m->g;
 	int i;
@@ -1137,18 +1130,17 @@ FILE *d;
 /*
  - at - print current situation
  == #ifdef REDEBUG
- == static void at(struct match *m, char *title, char *start, char *stop, \
- ==						sopno startst, sopno stopst);
+ == static void at(struct match *m, const char *title, const char *start, \
+ ==			 const char *stop, sopno startst, sopno stopst);
  == #endif
  */
 static void
-at(m, title, start, stop, startst, stopst)
-struct match *m;
-char *title;
-char *start;
-char *stop;
-sopno startst;
-sopno stopst;
+at(	struct match *m,
+	const char *title,
+	const char *start,
+	const char *stop,
+	sopno startst,
+	sopno stopst)
 {
 	if (!(m->eflags&REG_TRACE))
 		return;
@@ -1163,7 +1155,7 @@ sopno stopst;
 /*
  - pchar - make a character printable
  == #ifdef REDEBUG
- == static char *pchar(int ch);
+ == static const char *pchar(int ch);
  == #endif
  *
  * Is this identical to regchar() over in debug.c?  Well, yes.  But a
@@ -1171,9 +1163,8 @@ sopno stopst;
  * a matching debug.o, and this is convenient.  It all disappears in
  * the non-debug compilation anyway, so it doesn't matter much.
  */
-static char *			/* -> representation */
-pchar(ch)
-int ch;
+static const char *		/* -> representation */
+pchar(int ch)
 {
 	static char pbuf[10];