Do not discard subpatterns with {0} quantifiers, as they may be called as

subroutines.


git-svn-id: svn://vcs.exim.org/pcre/code/trunk@335 2f5784b3-3f2a-0410-8824-cb99058d5e15

1 files changed, 7 insertions, 4 deletions

diff --git a/HACKING b/HACKING
index c946cd2..e76341f 100644
--- a/HACKING
+++ b/HACKING
@@ -318,9 +318,12 @@ maximally respectively. All three are followed by LINK_SIZE bytes giving (as a
 positive number) the offset back to the matching bracket opcode.
 
 If a subpattern is quantified such that it is permitted to match zero times, it
-is preceded by one of OP_BRAZERO or OP_BRAMINZERO. These are single-byte
-opcodes which tell the matcher that skipping this subpattern entirely is a
-valid branch.
+is preceded by one of OP_BRAZERO, OP_BRAMINZERO, or OP_SKIPZERO. These are
+single-byte opcodes that tell the matcher that skipping the following
+subpattern entirely is a valid branch. In the case of the first two, not 
+skipping the pattern is also valid (greedy and non-greedy). The third is used 
+when a pattern has the quantifier {0,0}. It cannot be entirely discarded, 
+because it may be called as a subroutine from elsewhere in the regex.
 
 A subpattern with an indefinite maximum repetition is replicated in the
 compiled data its minimum number of times (or once with OP_BRAZERO if the
@@ -411,4 +414,4 @@ at compile time, and so does not cause anything to be put into the compiled
 data.
 
 Philip Hazel
-August 2007
+April 2008