Current ESP32 SDK does not support "std::optional"

console.cpp

@@ -34,14 +34,14 @@ uint8_t console::get_char()
 void console::operator()()
 {
 	while(!*terminate) {
-		auto c = wait_for_char(500);
+		int c = wait_for_char(500);
 
-		if (c.has_value() == false)
+		if (c == -1)
 			continue;
 
 		if (c == 3)
 			*terminate = true;
 		else
-			buffer.push_back(c.value());
+			buffer.push_back(c);
 	}
 }

console.h

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <atomic>
-#include <optional>
 #include <thread>
 #include <vector>
 
@@ -16,7 +15,7 @@ private:
 	std::vector<char>       buffer;
 
 protected:
-	virtual std::optional<char> wait_for_char(const int timeout) = 0;
+	virtual int wait_for_char(const int timeout) = 0;
 
 public:
 	console(std::atomic_bool *const terminate);

console_ncurses.cpp

@@ -25,14 +25,14 @@ console_ncurses::~console_ncurses()
 	endwin();
 }
 
-std::optional<char> console_ncurses::wait_for_char(const int timeout)
+int console_ncurses::wait_for_char(const int timeout)
 {
 	struct pollfd fds[] = { { STDIN_FILENO, POLLIN, timeout } };
 
 	if (poll(fds, 1, 0) == 1 && fds[0].revents)
 		return getch();
 
-	return { };
+	return -1;
 }
 
 void console_ncurses::put_char(const char c)

console_ncurses.h

@@ -11,7 +11,7 @@ private:
 	NEWWIN *w_main       { nullptr };
 
 protected:
-	std::optional<char> wait_for_char(const int timeout) override;
+	int wait_for_char(const int timeout) override;
 
 public:
 	console_ncurses(std::atomic_bool *const terminate);

console_posix.cpp

@@ -25,14 +25,14 @@ console_posix::~console_posix()
 		error_exit(true, "~console_posix: tcsetattr failed");
 }
 
-std::optional<char> console_posix::wait_for_char(const int timeout)
+int console_posix::wait_for_char(const int timeout)
 {
 	struct pollfd fds[] = { { STDIN_FILENO, POLLIN, timeout } };
 
 	if (poll(fds, 1, 0) == 1 && fds[0].revents)
 		return getchar();
 
-	return { };
+	return -1;
 }
 
 void console_posix::put_char(const char c)

console_posix.h

@@ -9,7 +9,7 @@ private:
 	struct termios org_tty_opts { 0 };
 
 protected:
-	std::optional<char> wait_for_char(const int timeout) override;
+	int wait_for_char(const int timeout) override;
 
 public:
 	console_posix(std::atomic_bool *const terminate);