Address review comments

include/yaml-cpp/depthguard.h

@@ -20,16 +20,18 @@ namespace YAML {
  * maximum depth.
  */
 class DeepRecursion : public ParserException {
-  int m_atDepth = 0;
 public:
-  // no custom dtor needed, but virtual dtor necessary to prevent slicing
   virtual ~DeepRecursion() = default;
 
-  // construct an exception explaining how deep you were
   DeepRecursion(int at_depth, const Mark& mark_, const std::string& msg_);
 
-  // query how deep you were when the exception was thrown
+  // Returns the recursion depth when the exception was thrown
-  int AtDepth() const;
+  int depth() const {
+    return m_depth;
+  }
+
+private:
+  int m_depth = 0;
 };
 
 /**
@@ -45,7 +47,6 @@ public:
  */
 template <int max_depth = 2000>
 class DepthGuard final /* final because non-virtual dtor */ {
-  int & m_depth;
 public:
   DepthGuard(int & depth_, const Mark& mark_, const std::string& msg_) : m_depth(depth_) {
     ++m_depth;
@@ -54,7 +55,6 @@ public:
     }
   }
 
-  // DepthGuard is neither copyable nor moveable.
   DepthGuard(const DepthGuard & copy_ctor) = delete;
   DepthGuard(DepthGuard && move_ctor) = delete;
   DepthGuard & operator=(const DepthGuard & copy_assign) = delete;
@@ -67,6 +67,9 @@ public:
   int current_depth() const {
     return m_depth;
   }
+
+private:
+    int & m_depth;
 };
 
 } // namespace YAML

src/depthguard.cpp

@@ -4,11 +4,7 @@ namespace YAML {
 
 DeepRecursion::DeepRecursion(int at_depth, const Mark& mark_, const std::string& msg_)
     : ParserException(mark_, msg_),
-      m_atDepth(at_depth) {
+      m_depth(at_depth) {
-}
-
-int DeepRecursion::AtDepth() const {
-  return m_atDepth;
 }
 
 } // namespace YAML

src/singledocparser.cpp

@@ -48,7 +48,7 @@ void SingleDocParser::HandleDocument(EventHandler& eventHandler) {
 }
 
 void SingleDocParser::HandleNode(EventHandler& eventHandler) {
-  DepthGuard depthguard(depth, m_scanner.mark(), ErrorMsg::BAD_FILE);
+  DepthGuard<2000> depthguard(depth, m_scanner.mark(), ErrorMsg::BAD_FILE);
 
   // an empty node *is* a possibility
   if (m_scanner.empty()) {

src/singledocparser.h

@@ -16,7 +16,6 @@
 namespace YAML {
 class CollectionStack;
 template <int> class DepthGuard; // depthguard.h
-class DeepRecursion; // an exception which may be thrown from excessive call stack recursion, see depthguard.h
 class EventHandler;
 class Node;
 class Scanner;
@@ -57,7 +56,6 @@ class SingleDocParser {
   anchor_t LookupAnchor(const Mark& mark, const std::string& name) const;
 
  private:
-  using DepthGuard = YAML::DepthGuard<2000>;
   int depth = 0;
   Scanner& m_scanner;
   const Directives& m_directives;

test/parser_test.cpp

@@ -1,3 +1,4 @@
+#include <yaml-cpp/depthguard.h>
 #include "yaml-cpp/parser.h"
 #include "yaml-cpp/exceptions.h"
 #include "mock_event_handler.h"
@@ -25,7 +26,7 @@ TEST(ParserTest, CVE_2017_5950) {
     Parser parser{input};
 
     NiceMock<MockEventHandler> handler;
-    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::ParserException);
+    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::DeepRecursion);
 }
 
 TEST(ParserTest, CVE_2018_20573) {
@@ -36,7 +37,7 @@ TEST(ParserTest, CVE_2018_20573) {
     Parser parser{input};
 
     NiceMock<MockEventHandler> handler;
-    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::ParserException);
+    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::DeepRecursion);
 }
 
 TEST(ParserTest, CVE_2018_20574) {
@@ -47,7 +48,7 @@ TEST(ParserTest, CVE_2018_20574) {
     Parser parser{input};
 
     NiceMock<MockEventHandler> handler;
-    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::ParserException);
+    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::DeepRecursion);
 }
 
 TEST(ParserTest, CVE_2019_6285) {
@@ -59,5 +60,5 @@ TEST(ParserTest, CVE_2019_6285) {
     Parser parser{input};
 
     NiceMock<MockEventHandler> handler;
-    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::ParserException);
+    EXPECT_THROW(parser.HandleNextDocument(handler), YAML::DeepRecursion);
 }