From 9e73177d5362c1986814f411961b712967dc5f97 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Mon, 23 Nov 2020 14:40:59 -0800
Subject: [PATCH] Do not reduce quantifiers if it affects which text will be
 matched

Quantifier reduction when using +?)* and +?)+ should not be done
as it affects which text will be matched.

This removes the need for the RQ_PQ_Q ReduceType, so remove the
enum entry and related switch case.

Test that these are the only two patterns affected by testing all
quantifier reduction tuples for both the captured and uncaptured
cases and making sure the matched text is the same for both.

Fixes [Bug #17341]
---
 regparse.c               |  9 +--------
 test/ruby/test_regexp.rb | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/regparse.c b/regparse.c
index 7639db3bbe..24ff5b9a18 100644
--- a/regparse.c
+++ b/regparse.c
@@ -2187,7 +2187,6 @@ enum ReduceType {
   RQ_AQ,       /* to '*?'   */
   RQ_QQ,       /* to '??'   */
   RQ_P_QQ,     /* to '+)??' */
-  RQ_PQ_Q      /* to '+?)?' */
 };
 
 static enum ReduceType const ReduceTypeTable[6][6] = {
@@ -2197,7 +2196,7 @@ static enum ReduceType const ReduceTypeTable[6][6] = {
   {RQ_A,    RQ_A,    RQ_DEL, RQ_ASIS, RQ_P_QQ, RQ_DEL},  /* '+'  */
   {RQ_DEL,  RQ_AQ,   RQ_AQ,  RQ_DEL,  RQ_AQ,   RQ_AQ},   /* '??' */
   {RQ_DEL,  RQ_DEL,  RQ_DEL, RQ_DEL,  RQ_DEL,  RQ_DEL},  /* '*?' */
-  {RQ_ASIS, RQ_PQ_Q, RQ_DEL, RQ_AQ,   RQ_AQ,   RQ_DEL}   /* '+?' */
+  {RQ_ASIS, RQ_ASIS, RQ_ASIS, RQ_AQ,  RQ_AQ,   RQ_DEL}   /* '+?' */
 };
 
 extern void
@@ -2234,12 +2233,6 @@ onig_reduce_nested_quantifier(Node* pnode, Node* cnode)
     c->lower  = 1;  c->upper = REPEAT_INFINITE;  c->greedy = 1;
     return ;
     break;
-  case RQ_PQ_Q:
-    p->target = cnode;
-    p->lower  = 0;  p->upper = 1;  p->greedy = 1;
-    c->lower  = 1;  c->upper = REPEAT_INFINITE;  c->greedy = 0;
-    return ;
-    break;
   case RQ_ASIS:
     p->target = cnode;
     return ;
diff --git a/test/ruby/test_regexp.rb b/test/ruby/test_regexp.rb
index e124fc7952..e9d1fc30d4 100644
--- a/test/ruby/test_regexp.rb
+++ b/test/ruby/test_regexp.rb
@@ -1196,6 +1196,20 @@ class TestRegexp < Test::Unit::TestCase
     }
   end
 
+  def test_quantifier_reduction
+    assert_equal('aa', eval('/(a+?)*/').match('aa')[0])
+    assert_equal('aa', eval('/(?:a+?)*/').match('aa')[0])
+
+    quantifiers = %w'? * + ?? *? +?'
+    quantifiers.each do |q1|
+      quantifiers.each do |q2|
+        r1 = eval("/(a#{q1})#{q2}/").match('aa')[0]
+        r2 = eval("/(?:a#{q1})#{q2}/").match('aa')[0]
+        assert_equal(r1, r2)
+      end
+    end
+  end
+
   def test_once
     pr1 = proc{|i| /#{i}/o}
     assert_equal(/0/, pr1.call(0))