Simplify C++ exceptions (#3380)

cpp/include/Ice/Exception.h

@@ -1,112 +1,49 @@
-//
-// Copyright (c) ZeroC, Inc. All rights reserved.
-//
+// Copyright (c) ZeroC, Inc.
 
 #ifndef ICE_EXCEPTION_H
 #define ICE_EXCEPTION_H
 
 #include "Config.h"
-#include "ValueF.h"
 
 #include <exception>
-#include <memory>
 #include <ostream>
-#include <string>
-#include <vector>
 
 namespace Ice
 {
-    /**
-     * Abstract base class for all Ice exceptions. It has only two derived classes: LocalException and UserException.
-     * \headerfile Ice/Ice.h
-     */
+    /// Abstract base class for all Ice exceptions. It has only two derived classes: LocalException and UserException.
+    /// \headerfile Ice/Ice.h
     class ICE_API Exception : public std::exception
     {
     public:
-        /**
-         * Constructs an exception with a default message.
-         * @param file The file where this exception is constructed. This C string is not copied.
-         * @param line The line where this exception is constructed.
-         */
-        Exception(const char* file, int line) noexcept;
-
-        /**
-         * Constructs an exception.
-         * @param file The file where this exception is constructed. This C string is not copied.
-         * @param line The line where this exception is constructed.
-         * @param message The error message adopted by this exception and returned by what().
-         */
-        Exception(const char* file, int line, std::string message);
-
-        /**
-         * Copy constructor.
-         * @param other The exception to copy.
-         */
-        Exception(const Exception& other) noexcept = default;
-
-        /**
-         * Assignment operator.
-         * @param rhs The exception to assign.
-         */
-        Exception& operator=(const Exception& rhs) noexcept = default;
-
-        /**
-         * Returns the error message of this exception.
-         * @return The error message.
-         */
-        [[nodiscard]] const char* what() const noexcept override;
-
-        /**
-         * Returns the type ID of this exception. This corresponds to the Slice type ID for Slice-defined exceptions,
-         * and to a similar fully scoped name for other exceptions. For example "::Ice::CommunicatorDestroyedException".
-         * @return The type ID of this exception
-         */
+        Exception() noexcept = default;
+        Exception(const Exception&) noexcept = default;
+        Exception& operator=(const Exception&) noexcept = default;
+
+        // Need out-of-line virtual function to avoid weak vtable, which in turn requires the default constructor,
+        // copy constructor, and copy assignment operator to be declared explicitly.
+        ~Exception() override;
+
+        /// Returns the type ID of this exception. This corresponds to the Slice type ID for Slice-defined exceptions,
+        /// and to a similar fully scoped name for other exceptions. For example
+        /// "::Ice::CommunicatorDestroyedException".
+        /// @return The type ID of this exception
         [[nodiscard]] virtual const char* ice_id() const noexcept = 0;
 
-        /**
-         * Outputs a description of this exception to a stream. This function is called by operator<<(std::ostream&,
-         * const Ice::Exception&). The default implementation outputs ice_id(). The application can override the
-         * ice_print of a user exception to produce a more detailed description, with typically the ice_id() plus
-         * additional information.
-         * @param os The output stream.
-         */
-        virtual void ice_print(std::ostream& os) const { os << ice_id(); }
-
-        /**
-         * Returns the name of the file where this exception was constructed.
-         * @return The file name.
-         */
-        [[nodiscard]] const char* ice_file() const noexcept;
-
-        /**
-         * Returns the line number where this exception was constructed.
-         * @return The line number.
-         */
-        [[nodiscard]] int ice_line() const noexcept;
-
-        /**
-         * Returns the stack trace at the point this exception was constructed.
-         * @return The stack trace as a string, or an empty string if stack trace collection is not enabled.
-         */
-        [[nodiscard]] std::string ice_stackTrace() const;
-
-        /**
-         * Enables the collection of stack traces for exceptions. On Windows, calling this function more than once is
-         * useful to refresh the symbol module list; on other platforms, the second and subsequent calls have no effect.
-         */
-        static void ice_enableStackTraceCollection();
-
-    private:
-        friend ICE_API std::ostream& operator<<(std::ostream&, const Exception&);
-
-        const char* _file;                                // can be nullptr
-        int _line;                                        // not used when _file is nullptr
-        std::shared_ptr<std::string> _whatString;         // shared storage for custom _what message.
-        const char* _what;                                // can be nullptr
-        std::shared_ptr<std::vector<void*>> _stackFrames; // shared storage for stack frames.
+        /// Outputs a description of this exception to a stream.
+        /// @param os The output stream.
+        virtual void ice_print(std::ostream& os) const = 0;
     };
 
-    ICE_API std::ostream& operator<<(std::ostream&, const Exception&);
+    /// Outputs a description of an Ice exception to a stream by calling the ice_print member function of this
+    /// exception.
+    /// @param os The output stream.
+    /// @param exception The exception to describe.
+    /// @return The output stream.
+    inline std::ostream& operator<<(std::ostream& os, const Exception& exception)
+    {
+        exception.ice_print(os);
+        return os;
+    }
 }
 
 #endif

cpp/include/Ice/LocalException.h

@@ -1,30 +1,57 @@
-//
-// Copyright (c) ZeroC, Inc. All rights reserved.
-//
+// Copyright (c) ZeroC, Inc.
 
 #ifndef ICE_LOCAL_EXCEPTION_H
 #define ICE_LOCAL_EXCEPTION_H
 
 #include "Exception.h"
 
+#include <memory>
+#include <string>
+#include <vector>
+
 namespace Ice
 {
-    /**
-     * Base class for all Ice exceptions not defined in Slice.
-     * \headerfile Ice/Ice.h
-     */
+    /// Base class for all Ice exceptions not defined in Slice.
+    /// \headerfile Ice/Ice.h
     class ICE_API LocalException : public Exception
     {
     public:
-        /**
-         * Constructs a local exception.
-         * @param file The file where this exception is constructed. This C string is not copied.
-         * @param line The line where this exception is constructed.
-         * @param message The error message adopted by this exception and returned by what().
-         */
-        LocalException(const char* file, int line, std::string message) : Exception(file, line, std::move(message)) {}
+        /// Constructs a local exception.
+        /// @param file The file where this exception is constructed. This C string is not copied.
+        /// @param line The line where this exception is constructed.
+        /// @param message The error message adopted by this exception and returned by what().
+        LocalException(const char* file, int line, std::string message);
+
+        /// Gets the error message of this local Ice exception.
+        /// @return The error message.
+        [[nodiscard]] const char* what() const noexcept final;
+
+        void ice_print(std::ostream& os) const final;
 
         [[nodiscard]] const char* ice_id() const noexcept override;
+
+        /// Gets the name of the file where this exception was constructed.
+        /// @return The file name.
+        [[nodiscard]] const char* ice_file() const noexcept;
+
+        /// Gets the line number where this exception was constructed.
+        /// @return The line number.
+        [[nodiscard]] int ice_line() const noexcept;
+
+        /// Gets the stack trace at the point this exception was constructed.
+        /// @return The stack trace as a string, or an empty string if stack trace collection is not enabled.
+        [[nodiscard]] std::string ice_stackTrace() const;
+
+        /// Enables the collection of stack traces for exceptions. On Windows, calling this function more than once is
+        /// useful to refresh the symbol module list; on other platforms, the second and subsequent calls have no
+        /// effect.
+        static void ice_enableStackTraceCollection();
+
+    private:
+        const char* _file;
+        int _line;
+        std::shared_ptr<std::string> _whatString;         // shared storage for custom _what message.
+        std::shared_ptr<std::vector<void*>> _stackFrames; // shared storage for stack frames.
     };
 }
 

cpp/include/Ice/LocalExceptions.h

@@ -82,6 +82,10 @@ namespace Ice
         {
         }
 
+        RequestFailedException(const RequestFailedException&) noexcept = default;
+        RequestFailedException& operator=(const RequestFailedException&) noexcept = default;
+        ~RequestFailedException() override; // to avoid weak vtable
+
     private:
         std::shared_ptr<Identity> _id;
         std::shared_ptr<std::string> _facet;

cpp/include/Ice/UserException.h

@@ -1,36 +1,29 @@
-//
-// Copyright (c) ZeroC, Inc. All rights reserved.
-//
+// Copyright (c) ZeroC, Inc.
 
 #ifndef ICE_USER_EXCEPTION_H
 #define ICE_USER_EXCEPTION_H
 
 #include "Exception.h"
 
-#include <string_view>
-
 namespace Ice
 {
     class InputStream;
     class OutputStream;
 
-    /**
-     * Abstract base class for all Ice exceptions defined in Slice.
-     * \headerfile Ice/Ice.h
-     */
+    /// Abstract base class for all Ice exceptions defined in Slice.
+    /// \headerfile Ice/Ice.h
     class ICE_API UserException : public Exception
     {
     public:
-        /**
-         * Default constructor. The file, line and what message are never set for user exceptions.
-         */
-        UserException() : Exception(nullptr, 0) {}
-
-        /**
-         * Throws this exception.
-         */
+        /// Throws this exception.
         virtual void ice_throw() const = 0;
 
+        /// Gets the Slice type ID of this user exception.
+        /// @return The Slice type ID.
+        [[nodiscard]] const char* what() const noexcept final;
+
+        void ice_print(std::ostream& os) const override;
+
         /// \cond STREAM
         // _write and _read are virtual for the Python, Ruby etc. mappings.
         virtual void _write(OutputStream*) const;

cpp/src/DataStorm/SessionI.cpp

@@ -766,7 +766,7 @@ SessionI::destroyImpl(const exception_ptr& ex)
             {
                 rethrow_exception(ex);
             }
-            catch (const Exception& e)
+            catch (const LocalException& e)
             {
                 out << "\n:" << e.what() << "\n" << e.ice_stackTrace();
             }