c++: CowException for handling errors/poisoned cows

Makefile

@@ -5,7 +5,7 @@ PROJECT=cow
 AUTHOR=Avril (Flanchan) <flanchan@cumallover.me>
 
 VERSION_MAJOR=0
-VERSION_MINOR=2.0r0
+VERSION_MINOR=2.0r1
 VERSION=$(VERSION_MAJOR).$(VERSION_MINOR)
 
 ifeq ($(PREFIX),)

include/cow.hpp

@@ -3,9 +3,20 @@
 #include "cow.h"
 
 #include <memory>
+#include <exception>
 
 #include "cow/slice.hpp"
 
+struct CowException : public std::exception
+{
+	inline CowException(cow_err_kind k) : kind(k){}
+
+	const char* what() const noexcept override;
+	inline ~CowException(){}
+
+	const cow_err_kind kind;
+};
+
 struct Cow : public _cow_util::Span<unsigned char> {
 	struct Fake;
 	Cow() = delete;

src/cow.cpp

@@ -29,11 +29,11 @@ Cow::_inner::~_inner() {
 }
 Cow::_inner::_inner(size_t sz) : cow(_cow_create_unboxed(sz)){
 	//TODO: Real exception type?
-	if(UNLIKELY(cow.poisoned)) throw "POISONED";
+	if(UNLIKELY(cow.poisoned)) throw CowException(cow_err());
 }
 Cow::_inner::_inner(cow_t* ptr) : cow(*ptr)
 {
-	if(UNLIKELY(cow.poisoned)) throw "POISONED";
+	if(UNLIKELY(cow.poisoned)) throw CowException(cow_err());
 	free(ptr);
 }
 
@@ -66,4 +66,10 @@ Cow::Fake Cow::Fake::Fake::from_real(const Cow& real) { return Fake(real); }
 Cow::Fake Cow::Fake::clone() const { return Fake(*static_cast<const Fake*>(this)); }
 cow_t* Cow::Fake::get_raw() const { return fake; }
 
+// Error
 
+const char* CowException::what() const noexcept { 
+	auto str = cow_err_msg(kind); 
+	if(str && *str) return *str;
+	else return "Unknown error";
+}

src/test/main.cpp

@@ -217,9 +217,12 @@ int main()
 	read_fake(clone); //clone still functions because of refcount on origin.
 
 	printf("Last error: %d, %s\n", cow_err(), *cow_err_msg(cow_err()));
-	Cow should_fail(SIZE_MAX);
-	printf("Last error: %d, %s\n", cow_err(), *cow_err_msg(cow_err()));
-	Cow::Fake should_fail_clone = should_fail;
+	try {
+		Cow should_fail(SIZE_MAX);
+		Cow::Fake should_fail_clone = should_fail;
+	} catch (CowException& cw) {
+		printf("Error! (%d) %s\n", cw.kind, cw.what());
+	}
 	printf("Last error: %d, %s\n", cow_err(), *cow_err_msg(cow_err()));
 	return 0;
 }