diff --git a/sys/man/2/regexp b/sys/man/2/regexp
index 7760dfe0e..a4b58969b 100644
--- a/sys/man/2/regexp
+++ b/sys/man/2/regexp
@@ -210,6 +210,8 @@ if
 is not matched.
 .SH BUGS
 There is no way to specify or match a NUL character; NULs terminate patterns and strings.
+The size of a character class and the number of sub-expression matches are hard-coded
+limits. The library uses the worst-case space estimate for allocating VM runtime threads.
 .SH HISTORY
 .IR Regexp (2)
 first appeared in Plan 9 from Bell Labs. This implementation was written from
diff --git a/sys/src/libregexp/regcomp.c b/sys/src/libregexp/regcomp.c
index 3bbc26ca9..094f94779 100644
--- a/sys/src/libregexp/regcomp.c
+++ b/sys/src/libregexp/regcomp.c
@@ -308,7 +308,7 @@ getnextr(Parselex *l)
 {
 	l->literal = 0;
 	if(l->done) {
-		l->rune = 0;
+		l->rune = L'\0';
 		return;
 	}
 	l->rawexp += chartorune(&l->rune, l->rawexp);
@@ -327,7 +327,7 @@ getnextrlit(Parselex *l)
 	l->literal = 1;
 	if(l->done) {
 		l->literal = 0;
-		l->rune = 0;
+		l->rune = L'\0';
 		return;
 	}
 	l->rawexp += chartorune(&l->rune, l->rawexp);
@@ -347,7 +347,7 @@ lex(Parselex *l)
 	if(l->literal)
 		return l->peeklex = LRUNE;
 	switch(l->rune){
-	case 0:
+	case L'\0':
 		return l->peeklex = LEND;
 	case L'*':
 	case L'?':
@@ -375,16 +375,20 @@ lex(Parselex *l)
 static int
 pcmp(void *va, void *vb)
 {
-	vlong n;
 	Rune *a, *b;
 
 	a = va;
 	b = vb;
 
-	n = (vlong)b[0] - (vlong)a[0];
-	if(n)
-		return n;
-	return (vlong)b[1] - (vlong)a[1];
+	if(a[0] < b[0])
+		return 1;
+	if(a[0] > b[0])
+		return -1;
+	if(a[1] < b[1])
+		return 1;
+	if(a[1] > b[1])
+		return -1;
+	return 0;
 }
 
 static void
@@ -460,7 +464,7 @@ getclass(Parselex *l)
 	q[2] = 0;
 }
 
-/* classes are in descending order */
+/* classes are in descending order see pcmp */
 static Renode*
 buildclassn(Parselex *l)
 {
diff --git a/sys/src/libregexp/regimpl.h b/sys/src/libregexp/regimpl.h
index 8785a27f0..8c8ac03a7 100644
--- a/sys/src/libregexp/regimpl.h
+++ b/sys/src/libregexp/regimpl.h
@@ -23,7 +23,7 @@ enum {
 	TSTAR,
 	TSUB,
 
-	NSUBEXPM = 32
+	NSUBEXPM = 32,
 };
 
 typedef struct Parselex Parselex;
@@ -31,30 +31,22 @@ typedef struct Renode Renode;
 
 struct Parselex {
 	/* Parse */
-	Renode *next;
-	Renode *nodes;
-	int sub;
-	int instrs;
+	Renode *next, *nodes;
+	int sub, instrs;
 	jmp_buf exitenv;
 	/* Lex */
 	void (*getnextr)(Parselex*);
-	char *rawexp;
-	char *orig;
+	char *rawexp, *orig;
 	Rune rune;
-	Rune peek;
-	int peeklex;
-	int done;
-	int literal;
+	int peek, peeklex, done, literal, nc;
 	Rune cpairs[400+2];
-	int nc;
 };
 
 struct Renode {
 	int op;
 	Renode *left;
 	Rune r;
-	union
-	{
+	union {
 		Rune r1;
 		int sub;
 		Renode *right;
@@ -73,13 +65,11 @@ struct Reinst {
 	char op;
 	int gen;
 	Reinst *a;
-	union
-	{
+	union {
 		Rune r;
 		int sub;
 	};
-	union
-	{
+	union {
 		Rune r1;
 		Reinst *b;
 	};