feat(cpp): add placeholders

Signed-off-by: Matej Focko <mfocko@redhat.com>

static/files/cpp/exceptions-and-raii/placeholders/placeholders.hpp

@@ -0,0 +1,77 @@
+#include <exception>
+#include <format>
+#include <string>
+
+class _todo : public std::exception {
+    std::string cause;
+
+   public:
+    _todo() : cause("not yet implemented") {}
+    _todo(std::string&& excuse) : cause("not yet implemented: " + excuse) {}
+    virtual const char* what() const throw() { return cause.c_str(); }
+};
+
+/**
+ * @brief Indicates unfinished code.
+ */
+void todo() { throw _todo(); }
+
+/**
+ * @brief Indicates unfinished code.
+ * @param fmt an object that represents the format string
+ * @param args arguments to be formatted
+ */
+template <class... Args>
+void todo(std::format_string<Args...> fmt, Args&&... args) {
+    throw _todo(std::format(fmt, args...));
+}
+
+class _unimplemented : public std::exception {
+    std::string cause;
+
+   public:
+    _unimplemented() : cause("not implemented") {}
+    _unimplemented(std::string&& excuse)
+        : cause("not implemented: " + excuse) {}
+    virtual const char* what() const throw() { return cause.c_str(); }
+};
+
+/**
+ * @brief Indicates unimplemented code by throwing with a message of “not implemented”.
+ */
+void unimplemented() { throw _unimplemented(); }
+
+/**
+ * @brief Indicates unimplemented code by throwing with a message of “not implemented”.
+ * @param fmt an object that represents the format string
+ * @param args arguments to be formatted
+ */
+template <class... Args>
+void unimplemented(std::format_string<Args...> fmt, Args&&... args) {
+    throw _unimplemented(std::format(fmt, args...));
+}
+
+class _unreachable : public std::exception {
+    std::string cause;
+
+   public:
+    _unreachable() : cause("entered unreachable code") {}
+    _unreachable(std::string&& excuse)
+        : cause("entered unreachable code: " + excuse) {}
+    virtual const char* what() const throw() { return cause.c_str(); }
+};
+
+/**
+ * @brief Indicates unreachable code.
+ */
+void unreachable() { throw _unreachable(); }
+
+/**
+ * @brief Indicates unreachable code.
+ * @param fmt an object that represents the format string
+ * @param args arguments to be formatted
+ */
+template <class... Args>
+void unreachable(std::format_string<Args...> fmt, Args&&... args) {
+    throw _unreachable(std::format(fmt, args...));
+}

static/files/cpp/exceptions-and-raii/placeholders/test.cpp

@@ -0,0 +1,6 @@
+#include "placeholders.hpp"
+
+int main() {
+  todo("finish later ({})", "in 3 days");
+  return 0;
+}