Fix minimum length bug for patterns containing (*ACCEPT).

ChangeLog

@@ -31,7 +31,13 @@ minimum is potentially useful.
 9. Some changes to the way the minimum subject length is handled:
 
    * When PCRE2_NO_START_OPTIMIZE is set, no minimum length is computed; 
-     pcre2test omits this item instead of showing a value of zero.
+     pcre2test now omits this item instead of showing a value of zero.
+     
+   * An incorrect minimum length could be calculated for a pattern that 
+     contained (*ACCEPT) inside a qualified group whose minimum repetition was 
+     zero, for example /A(?:(*ACCEPT))?B/, which incorrectly computed a minimum
+     of 2. The minimum length scan no longer happens for a pattern that 
+     contains (*ACCEPT).
      
    * When no minimum length is set by the normal scan, but a first and/or last 
      code unit is recorded, set the minimum to 1 or 2 as appropriate.

src/pcre2_compile.c

@@ -10039,8 +10039,9 @@ re->max_lookbehind = cb.max_lookbehind;
 
 if (cb.had_accept)
   {
-  reqcu = 0;              /* Must disable after (*ACCEPT) */
+  reqcu = 0;                     /* Must disable after (*ACCEPT) */
   reqcuflags = REQ_NONE;
+  re->flags |= PCRE2_HASACCEPT;  /* Disables minimum length */ 
   }
 
 /* Fill in the final opcode and check for disastrous overflow. If no overflow,

src/pcre2_internal.h

@@ -517,6 +517,7 @@ bytes in a code unit in that mode. */
 #define PCRE2_HASBKPORX     0x00100000  /* contains \P, \p, or \X */
 #define PCRE2_DUPCAPUSED    0x00200000  /* contains (?| */
 #define PCRE2_HASBKC        0x00400000  /* contains \C */
+#define PCRE2_HASACCEPT     0x00800000  /* contains (*ACCEPT) */
 
 #define PCRE2_MODE_MASK     (PCRE2_MODE8 | PCRE2_MODE16 | PCRE2_MODE32)
 

src/pcre2_study.c

@@ -1607,13 +1607,13 @@ if ((re->flags & (PCRE2_FIRSTSET|PCRE2_STARTLINE)) == 0)
   }
 
 /* Find the minimum length of subject string. If the pattern can match an empty
-string, the minimum length is already known. If there are more back references
+string, the minimum length is already known. If the pattern contains (*ACCEPT) 
-than the size of the vector we are going to cache them in, do nothing. A
+all bets are off. If there are more back references than the size of the vector
-pattern that complicated will probably take a long time to analyze and may in
+we are going to cache them in, do nothing. A pattern that complicated will
-any case turn out to be too complicated. Note that back reference minima are
+probably take a long time to analyze and may in any case turn out to be too
-held as 16-bit numbers. */
+complicated. Note that back reference minima are held as 16-bit numbers. */
 
-if ((re->flags & PCRE2_MATCH_EMPTY) == 0 &&
+if ((re->flags & (PCRE2_MATCH_EMPTY|PCRE2_HASACCEPT)) == 0 &&
      re->top_backref <= MAX_CACHE_BACKREF)
   {
   int backref_cache[MAX_CACHE_BACKREF+1];

testdata/testinput2

@@ -5623,4 +5623,6 @@ a)"xI
 
 /((?=a))[abcd]/I
 
+/A(?:(*ACCEPT))?B/info
+
 # End of testinput2

testdata/testoutput2

@@ -17026,6 +17026,11 @@ Capture group count = 1
 First code unit = 'a'
 Subject length lower bound = 1
 
+/A(?:(*ACCEPT))?B/info
+Capture group count = 0
+First code unit = 'A'
+Subject length lower bound = 1
+
 # End of testinput2
 Error -70: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data