Fix optimization bugs for patterns starting with lookaheads.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@1669 2f5784b3-3f2a-0410-8824-cb99058d5e15

1 files changed, 26 insertions, 23 deletions

diff --git a/pcre_compile.c b/pcre_compile.c
index 67c74e8..de92313 100644
--- a/pcre_compile.c
+++ b/pcre_compile.c
@@ -7918,15 +7918,17 @@ for (;; ptr++)
         }
       }
 
-    /* For a forward assertion, we take the reqchar, if set. This can be
-    helpful if the pattern that follows the assertion doesn't set a different
-    char. For example, it's useful for /(?=abcde).+/. We can't set firstchar
-    for an assertion, however because it leads to incorrect effect for patterns
-    such as /(?=a)a.+/ when the "real" "a" would then become a reqchar instead
-    of a firstchar. This is overcome by a scan at the end if there's no
-    firstchar, looking for an asserted first char. */
-
-    else if (bravalue == OP_ASSERT && subreqcharflags >= 0)
+    /* For a forward assertion, we take the reqchar, if set, provided that the
+    group has also set a first char. This can be helpful if the pattern that
+    follows the assertion doesn't set a different char. For example, it's
+    useful for /(?=abcde).+/. We can't set firstchar for an assertion, however
+    because it leads to incorrect effect for patterns such as /(?=a)a.+/ when
+    the "real" "a" would then become a reqchar instead of a firstchar. This is
+    overcome by a scan at the end if there's no firstchar, looking for an
+    asserted first char. */
+
+    else if (bravalue == OP_ASSERT && subreqcharflags >= 0 &&
+             subfirstcharflags >= 0)
       {
       reqchar = subreqchar;
       reqcharflags = subreqcharflags;
@@ -8715,8 +8717,8 @@ matching and for non-DOTALL patterns that start with .* (which must start at
 the beginning or after \n). As in the case of is_anchored() (see above), we
 have to take account of back references to capturing brackets that contain .*
 because in that case we can't make the assumption. Also, the appearance of .*
-inside atomic brackets or in a pattern that contains *PRUNE or *SKIP does not
-count, because once again the assumption no longer holds.
+inside atomic brackets or in an assertion, or in a pattern that contains *PRUNE
+or *SKIP does not count, because once again the assumption no longer holds.
 
 Arguments:
   code           points to start of expression (the bracket)
@@ -8725,13 +8727,14 @@ Arguments:
                   the less precise approach
   cd             points to the compile data
   atomcount      atomic group level
+  inassert       TRUE if in an assertion
 
 Returns:         TRUE or FALSE
 */
 
 static BOOL
 is_startline(const pcre_uchar *code, unsigned int bracket_map,
-  compile_data *cd, int atomcount)
+  compile_data *cd, int atomcount, BOOL inassert)
 {
 do {
    const pcre_uchar *scode = first_significant_code(
@@ -8758,7 +8761,7 @@ do {
        return FALSE;
 
        default:     /* Assertion */
-       if (!is_startline(scode, bracket_map, cd, atomcount)) return FALSE;
+       if (!is_startline(scode, bracket_map, cd, atomcount, TRUE)) return FALSE;
        do scode += GET(scode, 1); while (*scode == OP_ALT);
        scode += 1 + LINK_SIZE;
        break;
@@ -8772,7 +8775,7 @@ do {
    if (op == OP_BRA  || op == OP_BRAPOS ||
        op == OP_SBRA || op == OP_SBRAPOS)
      {
-     if (!is_startline(scode, bracket_map, cd, atomcount)) return FALSE;
+     if (!is_startline(scode, bracket_map, cd, atomcount, inassert)) return FALSE;
      }
 
    /* Capturing brackets */
@@ -8782,33 +8785,33 @@ do {
      {
      int n = GET2(scode, 1+LINK_SIZE);
      int new_map = bracket_map | ((n < 32)? (1 << n) : 1);
-     if (!is_startline(scode, new_map, cd, atomcount)) return FALSE;
+     if (!is_startline(scode, new_map, cd, atomcount, inassert)) return FALSE;
      }
 
    /* Positive forward assertions */
 
    else if (op == OP_ASSERT)
      {
-     if (!is_startline(scode, bracket_map, cd, atomcount)) return FALSE;
+     if (!is_startline(scode, bracket_map, cd, atomcount, TRUE)) return FALSE;
      }
 
    /* Atomic brackets */
 
    else if (op == OP_ONCE || op == OP_ONCE_NC)
      {
-     if (!is_startline(scode, bracket_map, cd, atomcount + 1)) return FALSE;
+     if (!is_startline(scode, bracket_map, cd, atomcount + 1, inassert)) return FALSE;
      }
 
    /* .* means "start at start or after \n" if it isn't in atomic brackets or
-   brackets that may be referenced, as long as the pattern does not contain
-   *PRUNE or *SKIP, because these break the feature. Consider, for example,
-   /.*?a(*PRUNE)b/ with the subject "aab", which matches "ab", i.e. not at the
-   start of a line. */
+   brackets that may be referenced or an assertion, as long as the pattern does
+   not contain *PRUNE or *SKIP, because these break the feature. Consider, for
+   example, /.*?a(*PRUNE)b/ with the subject "aab", which matches "ab", i.e.
+   not at the start of a line. */
 
    else if (op == OP_TYPESTAR || op == OP_TYPEMINSTAR || op == OP_TYPEPOSSTAR)
      {
      if (scode[1] != OP_ANY || (bracket_map & cd->backref_map) != 0 ||
-         atomcount > 0 || cd->had_pruneorskip)
+         atomcount > 0 || cd->had_pruneorskip || inassert)
        return FALSE;
      }
 
@@ -9663,7 +9666,7 @@ if ((re->options & PCRE_ANCHORED) == 0)
       re->flags |= PCRE_FIRSTSET;
       }
 
-    else if (is_startline(codestart, 0, cd, 0)) re->flags |= PCRE_STARTLINE;
+    else if (is_startline(codestart, 0, cd, 0, FALSE)) re->flags |= PCRE_STARTLINE;
     }
   }