Fix the schoolboy error with buffer allocation in base exception classes

2 files changed, 60 insertions, 53 deletions

diff --git a/project2/common/exceptions.cpp b/project2/common/exceptions.cpp
index 9be2710..29b4fa0 100644
--- a/project2/common/exceptions.cpp
+++ b/project2/common/exceptions.cpp
@@ -1,75 +1,71 @@
 #include <pch.hpp>
 #include "exceptions.h"
-#include "logger.h"
-#include <stdlib.h>
-#include <stdio.h>
 #include <error.h>
+#include <boost/format.hpp>
 
-numeric_error::numeric_error(int e) :
-	err(e),
-	buf(NULL)
+std::string
+sprintbf(boost::format & fmt)
 {
+	return fmt.str();
 }
 
-numeric_error::~numeric_error() throw()
+template <typename Arg, typename... Args>
+std::string
+sprintbf(boost::format & fmt, const Arg & arg, const Args & ... args)
 {
-	free(buf);
+	fmt % arg;
+	return sprintbf(fmt, args...);
+}
+
+template <typename... Args>
+std::string
+sprintbf(const std::string & fmt, const Args & ... args)
+{
+	boost::format f(fmt);
+	return sprintbf(f, args...);
 }
 
 const char *
-numeric_error::what() const throw()
+MsgBufferedException::what() const throw()
 {
 	if (!buf) {
-		if (asprintf(&buf, "%d", err) < 1) {
-			throw std::bad_alloc();
-		}
+		buf = msg();
 	}
-	return buf;
+	return buf->c_str();
 }
 
-two_part_error::two_part_error(const std::string & w1, const std::string & w2) :
-	what1(w1),
-	what2(w2),
-	buf(NULL)
+numeric_error::numeric_error(int e) :
+	err(e)
 {
 }
 
-two_part_error::~two_part_error() throw()
+std::string
+numeric_error::msg() const throw()
 {
-	free(buf);
+	return sprintbf("%d", err);
 }
 
-const char *
-two_part_error::what() const throw()
+two_part_error::two_part_error(const std::string & w1, const std::string & w2) :
+	what1(w1),
+	what2(w2)
 {
-	if (!buf) {
-		if (asprintf(&buf, "%s, %s", what1.c_str(), what2.c_str()) < 1) {
-			throw std::bad_alloc();
-		}
-	}
-	return buf;
 }
 
-
-syscall_error::syscall_error(int e) :
-	err(e),
-	buf(NULL)
+std::string
+two_part_error::msg() const throw()
 {
+	return sprintbf("%s, %s", what1, what2);
 }
 
-syscall_error::~syscall_error() throw()
+
+syscall_error::syscall_error(int e) :
+	err(e)
 {
-	free(buf);
 }
 
-const char *
-syscall_error::what() const throw()
+std::string
+syscall_error::msg() const throw()
 {
-	if (!buf) {
-		if (asprintf(&buf, "%s (%d)", strerror(err), err) < 1) {
-			throw std::bad_alloc();
-		}
-	}
-	return buf;
+	return sprintbf("%s (%d)", strerror(err), err);
 }
 
diff --git a/project2/common/exceptions.h b/project2/common/exceptions.h
index 9cdf6f0..123afc9 100644
--- a/project2/common/exceptions.h
+++ b/project2/common/exceptions.h
@@ -2,35 +2,46 @@
 #define EXCEPTION_H
 
 #include <stdexcept>
+#include <boost/optional.hpp>
 
-class numeric_error : public std::exception {
+class MsgBufferedException : public std::exception {
 	public:
-		numeric_error(int);
-		~numeric_error() throw();
+		inline ~MsgBufferedException() throw() { }
 		const char * what() const throw();
+	protected:
+		virtual std::string msg() const throw() = 0;
+	private:
+		mutable boost::optional<std::string> buf;
+};
+
+class numeric_error : public MsgBufferedException {
+	public:
+		numeric_error(int);
+	protected:
+		std::string msg() const throw();
 	private:
 		int err;
-		mutable char * buf;
 };
-class syscall_error : public std::exception {
+
+class syscall_error : public MsgBufferedException {
 	public:
 		syscall_error(int);
-		~syscall_error() throw();
-		const char * what() const throw();
+	protected:
+		std::string msg() const throw();
 	private:
 		int err;
-		mutable char * buf;
 };
-class two_part_error : public std::exception {
+
+class two_part_error : public MsgBufferedException {
 	public:
 		two_part_error(const std::string & what1, const std::string & what2);
-		~two_part_error() throw();
-		const char * what() const throw();
+	protected:
+		std::string msg() const throw();
 	private:
 		const std::string what1;
 		const std::string what2;
-		mutable char * buf;
 };
+
 #define StaticMessageException(Name, Text) \
 class Name : public std::runtime_error { \
 	public: \