Improve warning on zero-length chunks in RE

	Message-Id: <199806272359.TAA05436@monk.mps.ohio-state.edu>

p4raw-id: //depot/perl@1252

diff --git a/regcomp.c b/regcomp.c
index 5475d78..ca4da9c 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -93,7 +93,7 @@
  * Flags to be passed up and down.
  */
 #define        WORST           0       /* Worst case. */
-#define        HASWIDTH        0x1     /* Known never to match null string. */
+#define        HASWIDTH        0x1     /* Known to match non-null strings. */
 #define        SIMPLE          0x2     /* Simple enough to be STAR/PLUS operand. */
 #define        SPSTART         0x4     /* Starts with * or +. */
 #define TRYAGAIN       0x8     /* Weeded out a declaration. */
@@ -425,7 +425,8 @@ study_chunk(regnode **scanp, I32 *deltap, regnode *last, scan_data_t *data, U32
                if (!scan)              /* It was not CURLYX, but CURLY. */
                    scan = next;
                if (dowarn && (minnext + deltanext == 0) 
-                   && !(data->flags & (SF_HAS_PAR|SF_IN_PAR))) 
+                   && !(data->flags & (SF_HAS_PAR|SF_IN_PAR))
+                   && maxcount <= 10000) /* Complement check for big count */
                    warn("Strange *+?{} on zero-length expression");
                min += minnext * mincount;
                is_inf |= (maxcount == REG_INFTY && (minnext + deltanext) > 0
@@ -970,7 +971,7 @@ reg(I32 paren, I32 *flagp)
     I32 flags, oregflags = regflags, have_branch = 0, open = 0;
     char c;
 
-    *flagp = HASWIDTH; /* Tentatively. */
+    *flagp = 0;                                /* Tentatively. */
 
     /* Make an OPEN node, if parenthesized. */
     if (paren) {
@@ -1144,8 +1145,8 @@ reg(I32 paren, I32 *flagp)
        regtail(ret, br);               /* OPEN -> first. */
     } else if (paren != '?')           /* Not Conditional */
        ret = br;
-    if (!(flags&HASWIDTH))
-       *flagp &= ~HASWIDTH;
+    if (flags&HASWIDTH)
+       *flagp |= HASWIDTH;
     *flagp |= flags&SPSTART;
     lastbr = br;
     while (*regcomp_parse == '|') {
@@ -1161,8 +1162,8 @@ reg(I32 paren, I32 *flagp)
            return(NULL);
        regtail(lastbr, br);            /* BRANCH -> BRANCH. */
        lastbr = br;
-       if (!(flags&HASWIDTH))
-           *flagp &= ~HASWIDTH;
+       if (flags&HASWIDTH)
+           *flagp |= HASWIDTH;
        *flagp |= flags&SPSTART;
     }
 
@@ -1176,12 +1177,13 @@ reg(I32 paren, I32 *flagp)
            ender = reganode(CLOSE, parno);
            break;
        case '<':
-       case '>':
        case ',':
        case '=':
        case '!':
-           ender = reg_node(SUCCEED);
            *flagp &= ~HASWIDTH;
+           /* FALL THROUGH */
+       case '>':
+           ender = reg_node(SUCCEED);
            break;
        case 0:
            ender = reg_node(END);
@@ -1372,7 +1374,9 @@ regpiece(I32 *flagp)
            ret->flags = 0;
 
            if (min > 0)
-               *flagp = (WORST|HASWIDTH);
+               *flagp = WORST;
+           if (max > 0)
+               *flagp |= HASWIDTH;
            if (max && max < min)
                FAIL("Can't do {n,m} with n > m");
            if (!SIZE_ONLY) {
@@ -1396,7 +1400,7 @@ regpiece(I32 *flagp)
 
     nextchar();
 
-    *flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
+    *flagp = (op != '+') ? (WORST|SPSTART|HASWIDTH) : (WORST|HASWIDTH);
 
     if (op == '*' && (flags&SIMPLE)) {
        reginsert(STAR, ret);