Fix some warnings and optimise for size

Looks like removing printf drops about 10kB.

CMakeLists.txt

 pico_enable_stdio_usb(picowota 1)
 
 pico_add_extra_outputs(picowota)
+set_target_properties(picowota PROPERTIES COMPILE_FLAGS "-Wall -Os")
 
 target_include_directories(picowota PRIVATE ${CMAKE_CURRENT_LIST_DIR})
 

main.c

 
 #include "tcp_comm.h"
 
+#ifdef DEBUG
+#include <stdio.h>
+#include "pico/stdio_usb.h"
+#define DBG_PRINTF_INIT() stdio_usb_init()
+#define DBG_PRINTF(...) printf(__VA_ARGS__)
+#else
+#define DBG_PRINTF_INIT() { }
+#define DBG_PRINTF(...) { }
+#endif
+
 extern const char *wifi_ssid;
 extern const char *wifi_pass;
 critical_section_t critical_section;
 
 int main()
 {
-	stdio_init_all();
-
-	sleep_ms(1000);
+	DBG_PRINTF_INIT();
 
 	if (cyw43_arch_init()) {
-		printf("failed to initialise\n");
+		DBG_PRINTF("failed to initialise\n");
 		return 1;
 	}
 
 	cyw43_arch_enable_sta_mode();
 
-	printf("Connecting to WiFi...\n");
+	DBG_PRINTF("Connecting to WiFi...\n");
 	if (cyw43_arch_wifi_connect_timeout_ms(wifi_ssid, wifi_pass, CYW43_AUTH_WPA2_AES_PSK, 30000)) {
-		printf("failed to connect.\n");
+		DBG_PRINTF("failed to connect.\n");
 		return 1;
 	} else {
-		printf("Connected.\n");
+		DBG_PRINTF("Connected.\n");
 	}
 
 	critical_section_init(&critical_section);
 	for ( ; ; ) {
 		err_t err = tcp_comm_listen(tcp, TCP_PORT);
 		if (err != ERR_OK) {
-			printf("Failed to start server: %d\n", err);
+			DBG_PRINTF("Failed to start server: %d\n", err);
 			sleep_ms(1000);
 			continue;
 		}

tcp_comm.c

 
 #include "tcp_comm.h"
 
-#define DEBUG_printf printf
+#ifdef DEBUG
+#include <stdio.h>
+#define DEBUG_printf(...) printf(__VA_ARGS__)
+#else
+#define DEBUG_printf(...) { }
+#endif
+
 #define POLL_TIME_S 5
 
 #define COMM_MAX_NARG     5
 {
 	ctx->conn_state = CONN_STATE_WAIT_FOR_SYNC;
 	ctx->rx_bytes_needed = sizeof(uint32_t);
+
+	return 0;
 }
 
 static int tcp_comm_sync_complete(struct tcp_comm_ctx *ctx)
 
 static int tcp_comm_data_begin(struct tcp_comm_ctx *ctx, uint32_t data_len)
 {
-	const struct comm_command *cmd = ctx->cmd;
-
 	ctx->conn_state = CONN_STATE_READ_DATA;
 	ctx->rx_bytes_needed = data_len;
 
 		return tcp_comm_data_complete(ctx);
 	}
 
-
 	return 0;
 }