net/SocketDescriptor: add [[nodiscard]]

src/net/SocketDescriptor.cxx

@@ -214,7 +214,7 @@ int
 SocketDescriptor::GetIntOption(int level, int name, int fallback) const noexcept
 {
 	int value = fallback;
-	GetOption(level, name, &value, sizeof(value));
+	(void)GetOption(level, name, &value, sizeof(value));
 	return value;
 }
 

src/net/SocketDescriptor.hxx

@@ -39,17 +39,21 @@ protected:
 	   special type */
 	SOCKET fd;
 #else // !_WIN32
+	[[nodiscard]]
 	explicit constexpr SocketDescriptor(FileDescriptor _fd) noexcept
 		:FileDescriptor(_fd) {}
 #endif // !_WIN32
 
 public:
+	[[nodiscard]]
 	SocketDescriptor() = default;
 
 #ifdef _WIN32
+	[[nodiscard]]
 	explicit constexpr SocketDescriptor(SOCKET _fd) noexcept
 		:fd(_fd) {}
 #else // !_WIN32
+	[[nodiscard]]
 	explicit constexpr SocketDescriptor(int _fd) noexcept
 		:FileDescriptor(_fd) {}
 #endif // !_WIN32
@@ -69,6 +73,7 @@ public:
 	 * same as file descriptors (i.e. not on Windows).  Use this only
 	 * when you know what you're doing.
 	 */
+	[[nodiscard]]
 	static constexpr SocketDescriptor FromFileDescriptor(FileDescriptor fd) noexcept {
 		return SocketDescriptor(fd);
 	}
@@ -79,6 +84,7 @@ public:
 	 * same as file descriptors (i.e. not on Windows).  Use this only
 	 * when you know what you're doing.
 	 */
+	[[nodiscard]]
 	constexpr const FileDescriptor &ToFileDescriptor() const noexcept {
 		return *this;
 	}
@@ -110,6 +116,7 @@ public:
 	int GetProtocol() const noexcept;
 #endif // __linux__
 
+	[[nodiscard]]
 	static constexpr SocketDescriptor Undefined() noexcept {
 #ifdef _WIN32
 		return SocketDescriptor{INVALID_SOCKET};
@@ -133,10 +140,12 @@ public:
 	using FileDescriptor::CheckDuplicate;
 	using FileDescriptor::Close;
 #else
+	[[nodiscard]]
 	constexpr SOCKET Get() const noexcept {
 		return fd;
 	}
 
+	[[nodiscard]]
 	constexpr void Set(SOCKET _fd) noexcept {
 		fd = _fd;
 	}
@@ -145,6 +154,7 @@ public:
 		fd = INVALID_SOCKET;
 	}
 
+	[[nodiscard]]
 	constexpr SOCKET Steal() noexcept {
 		return std::exchange(fd, INVALID_SOCKET);
 	}
@@ -172,17 +182,22 @@ public:
 	 * @return True on success, False on failure
 	 * See man 2 socket for detailed information
 	 */
+	[[nodiscard]]
 	bool Create(int domain, int type, int protocol) noexcept;
 
 	/**
 	 * Like Create(), but enable non-blocking mode.
 	 */
+	[[nodiscard]]
 	bool CreateNonBlock(int domain, int type, int protocol) noexcept;
 
 #ifndef _WIN32
+	[[nodiscard]]
 	static bool CreateSocketPair(int domain, int type, int protocol,
 				     SocketDescriptor &a,
 				     SocketDescriptor &b) noexcept;
+
+	[[nodiscard]]
 	static bool CreateSocketPairNonBlock(int domain, int type, int protocol,
 					     SocketDescriptor &a,
 					     SocketDescriptor &b) noexcept;
@@ -194,6 +209,7 @@ public:
 	/**
 	 * @return the value size or 0 on error
 	 */
+	[[nodiscard]]
 	std::size_t GetOption(int level, int name,
 			      void *value, std::size_t size) const noexcept;
 
@@ -260,12 +276,19 @@ public:
 	bool AutoBind() const noexcept;
 #endif
 
+	[[nodiscard]]
 	bool Listen(int backlog) const noexcept;
 
+	[[nodiscard]]
 	SocketDescriptor Accept() const noexcept;
+
+	[[nodiscard]]
 	SocketDescriptor AcceptNonBlock() const noexcept;
+
+	[[nodiscard]]
 	SocketDescriptor AcceptNonBlock(StaticSocketAddress &address) const noexcept;
 
+	[[nodiscard]]
 	bool Connect(SocketAddress address) const noexcept;
 
 	[[gnu::pure]]
@@ -277,6 +300,7 @@ public:
 	/**
 	 * Wrapper for recv().
 	 */
+	[[nodiscard]]
 	ssize_t Receive(std::span<std::byte> dest, int flags=0) const noexcept;
 
 	/**
@@ -284,12 +308,15 @@ public:
 	 *
 	 * MSG_NOSIGNAL is implicitly added (if available).
 	 */
+	[[nodiscard]]
 	ssize_t Send(std::span<const std::byte> src, int flags=0) const noexcept;
 
+	[[nodiscard]]
 	ssize_t Read(std::span<std::byte> dest) const noexcept {
 		return Receive(dest);
 	}
 
+	[[nodiscard]]
 	ssize_t Write(std::span<const std::byte> src) const noexcept {
 		return Send(src);
 	}
@@ -298,16 +325,21 @@ public:
 	 * Wrapper for Receive() with MSG_DONTWAIT (not available on
 	 * Windows).
 	 */
+	[[nodiscard]]
 	ssize_t ReadNoWait(std::span<std::byte> dest) const noexcept;
 
 	/**
 	 * Wrapper for Receive() with MSG_DONTWAIT (not available on
 	 * Windows).
 	 */
+	[[nodiscard]]
 	ssize_t WriteNoWait(std::span<const std::byte> src) const noexcept;
 
 #ifdef _WIN32
+	[[nodiscard]]
 	int WaitReadable(int timeout_ms) const noexcept;
+
+	[[nodiscard]]
 	int WaitWritable(int timeout_ms) const noexcept;
 #else
 	using FileDescriptor::WaitReadable;
@@ -318,12 +350,14 @@ public:
 	/**
 	 * Receive a datagram and return the source address.
 	 */
+	[[nodiscard]]
 	ssize_t Read(void *buffer, std::size_t length,
 		     StaticSocketAddress &address) const noexcept;
 
 	/**
 	 * Send a datagram to the specified address.
 	 */
+	[[nodiscard]]
 	ssize_t Write(const void *buffer, std::size_t length,
 		      SocketAddress address) const noexcept;