From 9ad70096c828452c714e10083d3421cee0ea66d7 Mon Sep 17 00:00:00 2001
From: yhirose <yuji.hirose.bug@gmail.com>
Date: Sat, 9 Jan 2021 15:10:42 -0500
Subject: [PATCH] Another infinite loop grammar detection. Fix #133

---
 docs/native.wasm | Bin 349329 -> 349485 bytes
 peglib.h         |   4 +++-
 test/test2.cc    |   8 ++++++++
 test/test3.cc    |   5 +++++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/docs/native.wasm b/docs/native.wasm
index f6d0f321b1839152719e1cc10a6854eb038c54c9..9377c0c544d21390cb2ee107b9beedaff30ab493 100644
GIT binary patch
delta 478
zcmXX?ze^lJ6rOqS?d{>t!Gd1A;x3sT19u3vYkL!dhmA1=n-EB0q29Kp5>&9T3Q;Vk
z2q8^4NP=MHwF)T$Ig&rYG<K$nMJma+cMd#0X6AiA-aGzWKmAfa`()_q>%qVr4va<-
ziiZOu&tK^4;lJ1Ni}lap_jTFP*^i2@?9C}}3&)QYb*=7@a#Vu2Xi2)^ok&|p;bO#(
z!qH!jLte0*600nE)6Xefe$&%o<)zeP>Ovs0;cipBWppU0c#S48oLKfMr-tPxYLQb8
zvL&v{6GJ)iZ?grkxkEEfm(W-iq_L8d0^q?wW<st)T!%kf(hRHbWqvP0l(g@tS5t}6
zN%~a5tV3xQjrFqFH`51B;0pzrq!`~)+(wO@4Dk0XoRA>4QQ>sy?fH$X_<bCDRzni2
zp+Y%<WdSoK*ox<e+nBI{!Q&oiQKq?zk8+V^b_yTYq}3*0?PqueV7|DFn%wIo*c8Sr
dS1KVZWH!87lJ?2nd5gf_Eu=HN-H;DA{{b-4SbzWk

delta 142
zcmZ3xN_65%(G5#@m=3RMUdGeDjE513nShvi`!XJuz+lG5+keEfoM&b{v;9OeOEn|o
z`so#!EJ_@V*^UBkEDj3OGox56r{4w&aWN{exbZScF+&8Ur|V_0EaFgLbQH)^VsxMW
pEQ`gQ>x_gM6ORIu;{);O>e(z;rpugTlAkV>!=kZ$LI%s+Hvm{tEkOVP

diff --git a/peglib.h b/peglib.h
index 38d6276..b7910e0 100644
--- a/peglib.h
+++ b/peglib.h
@@ -2872,7 +2872,9 @@ private:
     };
 
     g["Sequence"] = [&](const SemanticValues &vs) {
-      if (vs.size() == 1) {
+      if (vs.empty()) {
+        return npd(dot());
+      } else if (vs.size() == 1) {
         return std::any_cast<std::shared_ptr<Ope>>(vs[0]);
       } else {
         std::vector<std::shared_ptr<Ope>> opes;
diff --git a/test/test2.cc b/test/test2.cc
index 4c60112..24a7eff 100644
--- a/test/test2.cc
+++ b/test/test2.cc
@@ -159,6 +159,14 @@ TEST_CASE("Infinite loop 7", "[infinite loop]") {
   REQUIRE(!pg);
 }
 
+TEST_CASE("Infinite loop 8", "[infinite loop]") {
+    parser pg(R"(
+        ROOT <- ('A' /)*
+    )");
+
+    REQUIRE(!pg);
+}
+
 TEST_CASE("Not infinite 1", "[infinite loop]") {
   parser pg(R"(
         Numbers <- Number* EOF
diff --git a/test/test3.cc b/test/test3.cc
index 377864e..c9e191d 100644
--- a/test/test3.cc
+++ b/test/test3.cc
@@ -42,6 +42,11 @@ TEST_CASE("PEG Expression", "[peg]")
     REQUIRE(exact(g, "Expression", "") == true);
     REQUIRE(exact(g, "Expression", " ") == false);
     REQUIRE(exact(g, "Expression", " a b ") == false);
+
+    // NOTE: The followings are actually allowed in the original Ford's paper...
+    REQUIRE(exact(g, "Expression", "a//b ") == true);
+    REQUIRE(exact(g, "Expression", "a // b ") == true);
+    REQUIRE(exact(g, "Expression", "a / / b ") == true);
 }
 
 TEST_CASE("PEG Sequence", "[peg]")