Fix anchoring bug in conditional subexpression.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@1739 2f5784b3-3f2a-0410-8824-cb99058d5e15

4 files changed, 22 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index ac42247..8eed174 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -32,6 +32,11 @@ negative class with no characters less than 0x100 followed by a positive class
 with only characters less than 0x100, the first class was incorrectly being   
 auto-possessified, causing incorrect match failures.
 
+6. If the only branch in a conditional subpattern was anchored, the whole 
+subpattern was treated as anchored, when it should not have been, since the 
+assumed empty second branch cannot be anchored. Demonstrated by test patterns 
+such as /(?(1)^())b/ or /(?(?=^))b/.
+
 
 Version 8.42 20-March-2018
 --------------------------
diff --git a/pcre_compile.c b/pcre_compile.c
index 3991d6c..6141fb3 100644
--- a/pcre_compile.c
+++ b/pcre_compile.c
@@ -8682,10 +8682,18 @@ do {
      if (!is_anchored(scode, new_map, cd, atomcount)) return FALSE;
      }
 
-   /* Positive forward assertions and conditions */
+   /* Positive forward assertion */
 
-   else if (op == OP_ASSERT || op == OP_COND)
+   else if (op == OP_ASSERT)
+     {
+     if (!is_anchored(scode, bracket_map, cd, atomcount)) return FALSE;
+     }
+
+   /* Condition; not anchored if no second branch */
+
+   else if (op == OP_COND)
      {
+     if (scode[GET(scode,1)] != OP_ALT) return FALSE;
      if (!is_anchored(scode, bracket_map, cd, atomcount)) return FALSE;
      }
 
diff --git a/testdata/testinput2 b/testdata/testinput2
index 8ba4dc4..3528de1 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -4257,4 +4257,7 @@ backtracking verbs. --/
     ab
     aaab 
 
+/(?(?=^))b/
+    abc
+
 /-- End of testinput2 --/
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index 61ed8d9..4ccda27 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -14721,4 +14721,8 @@ No need char
  0: ab
  1: a
 
+/(?(?=^))b/
+    abc
+ 0: b
+
 /-- End of testinput2 --/