std.os: WSAStartup is now called upon socket creation when needed

lib/std/os.zig

@@ -2724,6 +2724,9 @@ pub const SocketError = error{
 
     /// The socket type is not supported by the protocol.
     SocketTypeNotSupported,
+
+    /// The environment for socket control has not been initialised.
+    NotInitialised,
 } || UnexpectedError;
 
 pub fn socket(domain: u32, socket_type: u32, protocol: u32) SocketError!socket_t {
@@ -2731,7 +2734,19 @@ pub fn socket(domain: u32, socket_type: u32, protocol: u32) SocketError!socket_t
         // NOTE: windows translates the SOCK_NONBLOCK/SOCK_CLOEXEC flags into windows-analagous operations
         const filtered_sock_type = socket_type & ~@as(u32, SOCK_NONBLOCK | SOCK_CLOEXEC);
         const flags: u32 = if ((socket_type & SOCK_CLOEXEC) != 0) windows.ws2_32.WSA_FLAG_NO_HANDLE_INHERIT else 0;
-        const rc = try windows.WSASocketW(@bitCast(i32, domain), @bitCast(i32, filtered_sock_type), @bitCast(i32, protocol), null, 0, flags);
+        const rc = windows.WSASocketW(@bitCast(i32, domain), @bitCast(i32, filtered_sock_type), @bitCast(i32, protocol), null, 0, flags) catch |err| switch (err) {
+            error.NotInitialised => again: {
+                // Before a socket is made Windows requires WSAStartup to be called.
+                // Let's try doing that now, then make the socket again. If socket creation still fails then there is an underlying issue we cannot solve.
+                // WSAStartup is supposed to have a pair in the form of WSACleanup to call once all socket operations concluded.
+                // As of writing that function is never called.
+                _ = windows.WSAStartup(2, 2) catch {
+                    return error.NotInitialised;
+                };
+                break :again try windows.WSASocketW(@bitCast(i32, domain), @bitCast(i32, filtered_sock_type), @bitCast(i32, protocol), null, 0, flags);
+            },
+            else => return err,
+        };
         errdefer windows.closesocket(rc) catch unreachable;
         if ((socket_type & SOCK_NONBLOCK) != 0) {
             var mode: c_ulong = 1; // nonblocking

lib/std/os/windows.zig

@@ -1295,6 +1295,7 @@ pub fn WSASocketW(
             .WSAEMFILE => return error.ProcessFdQuotaExceeded,
             .WSAENOBUFS => return error.SystemResources,
             .WSAEPROTONOSUPPORT => return error.ProtocolNotSupported,
+            .WSANOTINITIALISED => return error.NotInitialised,
             else => |err| return unexpectedWSAError(err),
         }
     }