# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1730252684 -3600
# Node ID e4f2d6d0e869fceef7d2426fb3e6a43d333b6467

blok finally v C++

diff -r 000000000000 -r e4f2d6d0e869 Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,28 @@
+CXX ?= g++
+CXXFLAGS ?= -O2 -g3 -ggdb -Wall -Wno-sign-compare
+CXXFLAGS += --std=c++20
+CXXFLAGS += -fsanitize=undefined -fsanitize=address
+LDFLAGS ?=
+
+SRC = $(shell find -maxdepth 1 -name '*.cpp')
+BIN = $(shell find -maxdepth 1 -name '*.cpp' | xargs basename -s .cpp)
+
+all: $(BIN)
+
+.PHONY: all run clean
+
+clean:
+	$(RM) $(BIN)
+
+run: $(BIN)
+	@echo "\e[1;32mHappy path without exceptions:\e[0m"
+	@for bin in $(BIN); do ./$$bin     ; done
+	@echo; echo
+	@echo "\e[1;32mInterrupted by exceptions:\e[0m"
+	@for bin in $(BIN); do ./$$bin fail; done
+
+$(BIN): $(SRC)
+	$(CXX) $(CXXFLAGS) -o $(@) $(@).cpp $(LDFLAGS)
+
+# Blok finally při odchytávání výjimek: C++ vs. Java
+# https://blog.frantovo.cz/c/395/
diff -r 000000000000 -r e4f2d6d0e869 bad.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bad.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,26 @@
+#include <iostream>
+#include <exception>
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	void* data = malloc(486);
+	std::cout << "  allocated memory at: " << data << std::endl;
+	fxThrowing(fail, data);
+	free(data);
+	std::cout << "  freed memory at: " << data << std::endl;
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "bad";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}
\ No newline at end of file
diff -r 000000000000 -r e4f2d6d0e869 good-class-generic.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/good-class-generic.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,42 @@
+#include <iostream>
+#include <exception>
+
+template<typename T>
+class Resource {
+private:
+	Resource(const Resource&) = delete;
+	Resource& operator=(const Resource&) = delete;
+public:
+	T* data;
+	void(*dtor)(T*);
+
+	Resource(T* data, void(*dtor)(T*)) : data(data), dtor(dtor) {
+		std::cout << "  created resource for data at: " << data << std::endl;
+	}
+
+	virtual ~Resource() {
+		dtor(data);
+		std::cout << "  called destructor on: " << data << std::endl;
+	}
+};
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	Resource buf(malloc(486), free);
+	fxThrowing(fail, buf.data);
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "good-class-generic";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}
diff -r 000000000000 -r e4f2d6d0e869 good-class.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/good-class.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,41 @@
+#include <iostream>
+#include <exception>
+
+class Buffer {
+private:
+	Buffer(const Buffer&) = delete;
+	Buffer& operator=(const Buffer&) = delete;
+public:
+	size_t size;
+	void* data;
+
+	Buffer(size_t size) : size(size), data(malloc(size)) {
+		std::cout << "  allocated memory at: " << data << std::endl;
+	}
+
+	virtual ~Buffer() {
+		free(data);
+		std::cout << "  freed memory at: " << data << std::endl;
+	}
+};
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	Buffer buf(486);
+	fxThrowing(fail, buf.data);
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "good-class";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}
diff -r 000000000000 -r e4f2d6d0e869 good-finally.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/good-finally.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,36 @@
+#include <iostream>
+#include <exception>
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	void* data = malloc(486);
+	std::cout << "  allocated memory at: " << data << std::endl;
+
+	std::exception_ptr e;
+	try {
+		fxThrowing(fail, data);
+	} catch (...) {
+		e = std::current_exception();
+	}
+
+	// finally:
+	free(data);
+	std::cout << "  freed memory at: " << data << std::endl;
+
+	if (e) std::rethrow_exception(e);
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "good-finally";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}
\ No newline at end of file
diff -r 000000000000 -r e4f2d6d0e869 good-smart-pointer.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/good-smart-pointer.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,38 @@
+#include <iostream>
+#include <exception>
+#include <memory>
+
+/** not needed, just for logging */
+void* myMalloc(size_t size) {
+	void* ptr = ::malloc(size);
+	std::cout << "  allocated memory at: " << ptr << std::endl;
+	return ptr;
+}
+
+/** not needed, just for logging */
+void myFree(void* ptr) {
+	::free(ptr);
+	std::cout << "  freed memory at: " << ptr << std::endl;
+}
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	// std::shared_ptr<void> buf(malloc(486), free); // standard functions
+	std::shared_ptr<void> buf(myMalloc(486), myFree); // our ones with logging
+	fxThrowing(fail, buf.get());
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "good-smart-pointer";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}
diff -r 000000000000 -r e4f2d6d0e869 good-vector.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/good-vector.cpp	Wed Oct 30 02:44:44 2024 +0100
@@ -0,0 +1,24 @@
+#include <iostream>
+#include <exception>
+#include <vector>
+
+void fxThrowing(bool fail, void* data) {
+	std::cout << "  doing something with data " << data << std::endl;
+	if (fail) throw std::logic_error("error from fxThrowing()");
+}
+
+void fxAllocating(bool fail) {
+	std::vector<char> buf(486);
+	fxThrowing(fail, buf.data());
+}
+
+int main(int argc, char** argv) {
+	bool fail = argc == 2 && std::string("fail") == argv[1];
+	const char* name = "good-vector";
+	std::cout << name << " (fail=" << fail << ")\n";
+	try {
+		fxAllocating(fail);
+	} catch (const std::exception& e) {
+		std::cout << "  caught exception: " << e.what() << std::endl;
+	}
+}