Merge pull request #211 from cdunn2001/except

* Add Json::Exception and derivatives.
* Clarify when exceptions are thrown, to avoid crashes caused by malicious input.
* Use our own type (derived fro std::exception) so they are trappable.

include/json/assertions.h

@@ -13,22 +13,30 @@
 #include "config.h"
 #endif // if !defined(JSON_IS_AMALGAMATION)
 
+/** It should not be possible for a maliciously designed file to
+ *  cause an abort() or seg-fault, so these macros are used only
+ *  for pre-condition violations and internal logic errors.
+ */
 #if JSON_USE_EXCEPTION
-#include <stdexcept>
-#define JSON_ASSERT(condition)                                                 \
-  {if (!(condition)) {throw std::logic_error( "assert json failed" );}} // @todo <= add detail about condition in exception
-#define JSON_FAIL_MESSAGE(message)                                             \
+
+// @todo <= add detail about condition in exception
+# define JSON_ASSERT(condition)                                                \
+  {if (!(condition)) {Json::throwLogicError( "assert json failed" );}}
+
+# define JSON_FAIL_MESSAGE(message)                                            \
   {                                                                            \
     std::ostringstream oss; oss << message;                                    \
-    throw std::logic_error(oss.str());                                         \
+    Json::throwLogicError(oss.str());                                          \
+    abort();                                                                   \
   }
-//#define JSON_FAIL_MESSAGE(message) throw std::logic_error(message)
+
 #else // JSON_USE_EXCEPTION
-#define JSON_ASSERT(condition) assert(condition)
+
+# define JSON_ASSERT(condition) assert(condition)
 
 // The call to assert() will show the failure message in debug builds. In
-// release bugs we abort, for a core-dump or debugger.
-#define JSON_FAIL_MESSAGE(message)                                             \
+// release builds we abort, for a core-dump or debugger.
+# define JSON_FAIL_MESSAGE(message)                                            \
   {                                                                            \
     std::ostringstream oss; oss << message;                                    \
     assert(false && oss.str().c_str());                                        \

include/json/value.h

@@ -11,6 +11,7 @@
 #endif // if !defined(JSON_IS_AMALGAMATION)
 #include <string>
 #include <vector>
+#include <exception>
 
 #ifndef JSON_USE_CPPTL_SMALLMAP
 #include <map>
@@ -32,6 +33,23 @@
  */
 namespace Json {
 
+/** Base class for all exceptions we throw.
+ */
+class JSON_API Exception;
+/** Exceptions which the user cannot easily avoid.
+ *
+ * E.g. out-of-memory, stack-overflow, malicious input
+ */
+class JSON_API RuntimeError;
+/** Exceptions throw by JSON_ASSERT/JSON_FAIL macros.
+ *
+ * These are precondition-violations (user bugs) and internal errors (our bugs).
+ */
+class JSON_API LogicError;
+
+JSON_API void throwRuntimeError(std::string const& msg);
+JSON_API void throwLogicError(std::string const& msg);
+
 /** \brief Type of the value held by a Value object.
  */
 enum ValueType {

include/json/writer.h

@@ -46,7 +46,7 @@ public:
   /** Write Value into document as configured in sub-class.
       Do not take ownership of sout, but maintain a reference during function.
       \pre sout != NULL
-      \return zero on success
+      \return zero on success (For now, we always return zero, so check the stream instead.)
       \throw std::exception possibly, depending on configuration
    */
   virtual int write(Value const& root, std::ostream* sout) = 0;

src/lib_json/json_reader.cpp

@@ -17,7 +17,6 @@
 #include <sstream>
 #include <memory>
 #include <set>
-#include <stdexcept>
 
 #if defined(_MSC_VER) && _MSC_VER < 1500 // VC++ 8.0 and below
 #define snprintf _snprintf
@@ -148,7 +147,7 @@ bool Reader::readValue() {
   // But this deprecated class has a security problem: Bad input can
   // cause a seg-fault. This seems like a fair, binary-compatible way
   // to prevent the problem.
-  if (stackDepth_g >= stackLimit_g) throw std::runtime_error("Exceeded stackLimit in readValue().");
+  if (stackDepth_g >= stackLimit_g) throwRuntimeError("Exceeded stackLimit in readValue().");
   ++stackDepth_g;
 
   Token token;
@@ -1107,7 +1106,7 @@ bool OurReader::parse(const char* beginDoc,
 }
 
 bool OurReader::readValue() {
-  if (stackDepth_ >= features_.stackLimit_) throw std::runtime_error("Exceeded stackLimit in readValue().");
+  if (stackDepth_ >= features_.stackLimit_) throwRuntimeError("Exceeded stackLimit in readValue().");
   ++stackDepth_;
   Token token;
   skipCommentTokens(token);
@@ -1431,7 +1430,7 @@ bool OurReader::readObject(Token& tokenStart) {
       return addErrorAndRecover(
           "Missing ':' after object member name", colon, tokenObjectEnd);
     }
-    if (name.length() >= (1U<<30)) throw std::runtime_error("keylength >= 2^30");
+    if (name.length() >= (1U<<30)) throwRuntimeError("keylength >= 2^30");
     if (features_.rejectDupKeys_ && currentValue().isMember(name)) {
       std::string msg = "Duplicate key: '" + name + "'";
       return addErrorAndRecover(
@@ -1994,7 +1993,7 @@ std::istream& operator>>(std::istream& sin, Value& root) {
             "Error from reader: %s",
             errs.c_str());
 
-    JSON_FAIL_MESSAGE("reader error");
+    throwRuntimeError("reader error");
   }
   return sin;
 }

src/lib_json/json_value.cpp

@@ -87,9 +87,11 @@ static inline char* duplicateStringValue(const char* value,
     length = Value::maxInt - 1;
 
   char* newString = static_cast<char*>(malloc(length + 1));
-  JSON_ASSERT_MESSAGE(newString != 0,
-                      "in Json::Value::duplicateStringValue(): "
-                      "Failed to allocate string value buffer");
+  if (newString == NULL) {
+    throwRuntimeError(
+        "in Json::Value::duplicateStringValue(): "
+        "Failed to allocate string value buffer");
+  }
   memcpy(newString, value, length);
   newString[length] = 0;
   return newString;
@@ -108,9 +110,11 @@ static inline char* duplicateAndPrefixStringValue(
                       "length too big for prefixing");
   unsigned actualLength = length + sizeof(unsigned) + 1U;
   char* newString = static_cast<char*>(malloc(actualLength));
-  JSON_ASSERT_MESSAGE(newString != 0,
-                      "in Json::Value::duplicateAndPrefixStringValue(): "
-                      "Failed to allocate string value buffer");
+  if (newString == 0) {
+    throwRuntimeError(
+        "in Json::Value::duplicateAndPrefixStringValue(): "
+        "Failed to allocate string value buffer");
+  }
   *reinterpret_cast<unsigned*>(newString) = length;
   memcpy(newString + sizeof(unsigned), value, length);
   newString[actualLength - 1U] = 0; // to avoid buffer over-run accidents by users later
@@ -148,6 +152,47 @@ static inline void releaseStringValue(char* value) { free(value); }
 
 namespace Json {
 
+class JSON_API Exception : public std::exception {
+public:
+  Exception(std::string const& msg);
+  virtual ~Exception() throw();
+  virtual char const* what() const throw();
+protected:
+  std::string const& msg_;
+};
+class JSON_API RuntimeError : public Exception {
+public:
+  RuntimeError(std::string const& msg);
+};
+class JSON_API LogicError : public Exception {
+public:
+  LogicError(std::string const& msg);
+};
+
+Exception::Exception(std::string const& msg)
+  : msg_(msg)
+{}
+Exception::~Exception() throw()
+{}
+char const* Exception::what() const throw()
+{
+  return msg_.c_str();
+}
+RuntimeError::RuntimeError(std::string const& msg)
+  : Exception(msg)
+{}
+LogicError::LogicError(std::string const& msg)
+  : Exception(msg)
+{}
+void throwRuntimeError(std::string const& msg)
+{
+  throw RuntimeError(msg);
+}
+void throwLogicError(std::string const& msg)
+{
+  throw LogicError(msg);
+}
+
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////

src/lib_json/json_writer.cpp

@@ -12,7 +12,6 @@
 #include <sstream>
 #include <utility>
 #include <set>
-#include <stdexcept>
 #include <assert.h>
 #include <math.h>
 #include <stdio.h>
@@ -1080,7 +1079,7 @@ StreamWriter* StreamWriterBuilder::newStreamWriter() const
   } else if (cs_str == "None") {
     cs = CommentStyle::None;
   } else {
-    throw std::runtime_error("commentStyle must be 'All' or 'None'");
+    throwRuntimeError("commentStyle must be 'All' or 'None'");
   }
   std::string colonSymbol = " : ";
   if (eyc) {

src/test_lib_json/main.cpp

@@ -6,7 +6,6 @@
 #include "jsontest.h"
 #include <json/config.h>
 #include <json/json.h>
-#include <stdexcept>
 #include <cstring>
 
 // Make numeric limits more convenient to talk about.