diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 5d9450d..9da345f 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -2564,14 +2564,22 @@
 	if ((flags & SPSTART || OP(scan) == BOW || OP(scan) == EOW)
 							  && !(flags & HASNL))
 	{
+	    size_t  scanlen;
+
 	    longest = NULL;
 	    len = 0;
 	    for (; scan != NULL; scan = regnext(scan))
-		if (OP(scan) == EXACTLY && STRLEN(OPERAND(scan)) >= (size_t)len)
+	    {
+		if (OP(scan) == EXACTLY)
 		{
-		    longest = OPERAND(scan);
-		    len = (int)STRLEN(OPERAND(scan));
+		    scanlen = STRLEN(OPERAND(scan));
+		    if (scanlen >= (size_t)len)
+		    {
+			longest = OPERAND(scan);
+			len = (int)scanlen;
+		    }
 		}
+	    }
 	    r->regmust = longest;
 	    r->regmlen = len;
 	}
@@ -3406,8 +3414,7 @@
 		{
 		    colnr_T pos_col = pos->lnum == rex.lnum + rex.reg_firstlnum
 							  && pos->col == MAXCOL
-				      ? (colnr_T)STRLEN(reg_getline(
-						pos->lnum - rex.reg_firstlnum))
+				      ? reg_getline_len(pos->lnum - rex.reg_firstlnum)
 				      : pos->col;
 
 		    if ((pos->lnum == rex.lnum + rex.reg_firstlnum
@@ -4695,7 +4702,7 @@
 				// right.
 				if (rex.line == NULL)
 				    break;
-				rex.input = rex.line + STRLEN(rex.line);
+				rex.input = rex.line + reg_getline_len(rex.lnum);
 				fast_breakcheck();
 			    }
 			    else
@@ -5249,8 +5256,10 @@
 {
     char	    *p;
     static char	    buf[50];
+    static size_t   buflen = 0;
 
     STRCPY(buf, ":");
+    buflen = 1;
 
     switch ((int) OP(op))
     {
@@ -5491,7 +5500,7 @@
       case MOPEN + 7:
       case MOPEN + 8:
       case MOPEN + 9:
-	sprintf(buf + STRLEN(buf), "MOPEN%d", OP(op) - MOPEN);
+	buflen += sprintf(buf + buflen, "MOPEN%d", OP(op) - MOPEN);
 	p = NULL;
 	break;
       case MCLOSE + 0:
@@ -5506,7 +5515,7 @@
       case MCLOSE + 7:
       case MCLOSE + 8:
       case MCLOSE + 9:
-	sprintf(buf + STRLEN(buf), "MCLOSE%d", OP(op) - MCLOSE);
+	buflen += sprintf(buf + buflen, "MCLOSE%d", OP(op) - MCLOSE);
 	p = NULL;
 	break;
       case BACKREF + 1:
@@ -5518,7 +5527,7 @@
       case BACKREF + 7:
       case BACKREF + 8:
       case BACKREF + 9:
-	sprintf(buf + STRLEN(buf), "BACKREF%d", OP(op) - BACKREF);
+	buflen += sprintf(buf + buflen, "BACKREF%d", OP(op) - BACKREF);
 	p = NULL;
 	break;
       case NOPEN:
@@ -5537,7 +5546,7 @@
       case ZOPEN + 7:
       case ZOPEN + 8:
       case ZOPEN + 9:
-	sprintf(buf + STRLEN(buf), "ZOPEN%d", OP(op) - ZOPEN);
+	buflen += sprintf(buf + buflen, "ZOPEN%d", OP(op) - ZOPEN);
 	p = NULL;
 	break;
       case ZCLOSE + 1:
@@ -5549,7 +5558,7 @@
       case ZCLOSE + 7:
       case ZCLOSE + 8:
       case ZCLOSE + 9:
-	sprintf(buf + STRLEN(buf), "ZCLOSE%d", OP(op) - ZCLOSE);
+	buflen += sprintf(buf + buflen, "ZCLOSE%d", OP(op) - ZCLOSE);
 	p = NULL;
 	break;
       case ZREF + 1:
@@ -5561,7 +5570,7 @@
       case ZREF + 7:
       case ZREF + 8:
       case ZREF + 9:
-	sprintf(buf + STRLEN(buf), "ZREF%d", OP(op) - ZREF);
+	bulen += sprintf(buf + buflen, "ZREF%d", OP(op) - ZREF);
 	p = NULL;
 	break;
 #endif
@@ -5602,7 +5611,7 @@
       case BRACE_COMPLEX + 7:
       case BRACE_COMPLEX + 8:
       case BRACE_COMPLEX + 9:
-	sprintf(buf + STRLEN(buf), "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
+	buflen += sprintf(buf + buflen, "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
 	p = NULL;
 	break;
       case MULTIBYTECODE:
@@ -5612,12 +5621,12 @@
 	p = "NEWL";
 	break;
       default:
-	sprintf(buf + STRLEN(buf), "corrupt %d", OP(op));
+	buflen += sprintf(buf + buflen, "corrupt %d", OP(op));
 	p = NULL;
 	break;
     }
     if (p != NULL)
-	STRCAT(buf, p);
+	STRCPY(buf + buflen, p);
     return (char_u *)buf;
 }
 #endif	    // DEBUG