Fix looping bug by recognizing that a conditional with only one branch may

match an empty string.


git-svn-id: svn://vcs.exim.org/pcre/code/trunk@395 2f5784b3-3f2a-0410-8824-cb99058d5e15

4 files changed, 28 insertions, 12 deletions

diff --git a/pcre_compile.c b/pcre_compile.c
index cfd803d..bac03da 100644
--- a/pcre_compile.c
+++ b/pcre_compile.c
@@ -1663,18 +1663,26 @@ for (code = first_significant_code(code + _pcre_OP_lengths[*code], NULL, 0, TRUE
     {
     BOOL empty_branch;
     if (GET(code, 1) == 0) return TRUE;    /* Hit unclosed bracket */
-
-    /* Scan a closed bracket */
-
-    empty_branch = FALSE;
-    do
-      {
-      if (!empty_branch && could_be_empty_branch(code, endcode, utf8))
-        empty_branch = TRUE;
+    
+    /* If a conditional group has only one branch, there is a second, implied, 
+    empty branch, so just skip over the conditional, because it could be empty.
+    Otherwise, scan the individual branches of the group. */
+    
+    if (c == OP_COND && code[GET(code, 1)] != OP_ALT)
       code += GET(code, 1);
+    else
+      {       
+      empty_branch = FALSE;
+      do
+        {
+        if (!empty_branch && could_be_empty_branch(code, endcode, utf8))
+          empty_branch = TRUE;
+        code += GET(code, 1);
+        }
+      while (*code == OP_ALT);
+      if (!empty_branch) return FALSE;   /* All branches are non-empty */
       }
-    while (*code == OP_ALT);
-    if (!empty_branch) return FALSE;   /* All branches are non-empty */
+        
     c = *code;
     continue;
     }
diff --git a/pcre_exec.c b/pcre_exec.c
index 21cc990..afdd88f 100644
--- a/pcre_exec.c
+++ b/pcre_exec.c
@@ -635,7 +635,7 @@ for (;;)
   {
   minimize = possessive = FALSE;
   op = *ecode;
-
+  
   /* For partial matching, remember if we ever hit the end of the subject after
   matching at least one subject character. */
 
@@ -880,7 +880,7 @@ for (;;)
         goto TAIL_RECURSE;
         }
       }
-    else                         /* Condition false & no 2nd alternative */
+    else                         /* Condition false & no alternative */
       {
       ecode += 1 + LINK_SIZE;
       }
diff --git a/testdata/testinput1 b/testdata/testinput1
index ecfd365..8b0caa4 100644
--- a/testdata/testinput1
+++ b/testdata/testinput1
@@ -4061,4 +4061,7 @@
 /(?(?=.*b).*b|^d)/
     abc
 
+/^%((?(?=[a])[^%])|b)*%$/
+    %ab%
+
 / End of testinput1 /
diff --git a/testdata/testoutput1 b/testdata/testoutput1
index 83ef39c..81b0cb8 100644
--- a/testdata/testoutput1
+++ b/testdata/testoutput1
@@ -6641,4 +6641,9 @@ No match
     abc
  0: ab
 
+/^%((?(?=[a])[^%])|b)*%$/
+    %ab%
+ 0: %ab%
+ 1: 
+
 / End of testinput1 /