diff --git a/CMakeLists.txt b/CMakeLists.txt
index 735cf22..66add69 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,6 +19,12 @@ add_subdirectory(blink)
 # Add hello world example
 add_subdirectory(hello_world)
 
+add_compile_options(-Wall
+        -Wno-format          # int != int32_t as far as the compiler is concerned because gcc has int32_t as long int
+        -Wno-unused-function # we have some for the docs that aren't called
+        -Wno-maybe-uninitialized
+        )
+
 # Hardware-specific examples in subdirectories:
 add_subdirectory(adc)
 add_subdirectory(clocks)
diff --git a/i2c/lcd_1602_i2c/lcd_1602_i2c.c b/i2c/lcd_1602_i2c/lcd_1602_i2c.c
index c23a77f..7ab27fe 100644
--- a/i2c/lcd_1602_i2c/lcd_1602_i2c.c
+++ b/i2c/lcd_1602_i2c/lcd_1602_i2c.c
@@ -144,7 +144,7 @@ int main() {
 
     lcd_init();
 
-    static uint8_t *message[] =
+    static char *message[] =
             {
                     "RP2040 by", "Raspberry Pi",
                     "A brand new", "microcontroller",
diff --git a/multicore/multicore_runner/multicore_runner.c b/multicore/multicore_runner/multicore_runner.c
index 9a5ec93..3f89a90 100644
--- a/multicore/multicore_runner/multicore_runner.c
+++ b/multicore/multicore_runner/multicore_runner.c
@@ -37,7 +37,7 @@ int32_t fibonacci(int32_t n) {
     if (n == 0) return 0;
     if (n == 1) return 1;
 
-    int n1 = 0, n2 = 1, n3;
+    int n1 = 0, n2 = 1, n3 = 0;
 
     for (int i = 2; i <= n; i++) {
         n3 = n1 + n2;
diff --git a/multicore/multicore_runner_queue/multicore_runner_queue.c b/multicore/multicore_runner_queue/multicore_runner_queue.c
index b0e2ec6..937adf3 100644
--- a/multicore/multicore_runner_queue/multicore_runner_queue.c
+++ b/multicore/multicore_runner_queue/multicore_runner_queue.c
@@ -50,7 +50,7 @@ int32_t fibonacci(int32_t n) {
     if (n == 0) return 0;
     if (n == 1) return 1;
 
-    int n1 = 0, n2 = 1, n3;
+    int n1 = 0, n2 = 1, n3 = 0;
 
     for (int i = 2; i <= n; i++) {
         n3 = n1 + n2;
diff --git a/pio/i2c/pio_i2c.c b/pio/i2c/pio_i2c.c
index 977553f..35e0530 100644
--- a/pio/i2c/pio_i2c.c
+++ b/pio/i2c/pio_i2c.c
@@ -32,7 +32,11 @@ void pio_i2c_rx_enable(PIO pio, uint sm, bool en) {
 static inline void pio_i2c_put16(PIO pio, uint sm, uint16_t data) {
     while (pio_sm_is_tx_fifo_full(pio, sm))
         ;
+    // some versions of GCC dislike this
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
     *(io_rw_16 *)&pio->txf[sm] = data;
+#pragma GCC diagnostic pop
 }
 
 
@@ -43,7 +47,11 @@ void pio_i2c_put_or_err(PIO pio, uint sm, uint16_t data) {
             return;
     if (pio_i2c_check_error(pio, sm))
         return;
+    // some versions of GCC dislike this
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
     *(io_rw_16 *)&pio->txf[sm] = data;
+#pragma GCC diagnostic pop
 }
 
 uint8_t pio_i2c_get(PIO pio, uint sm) {
diff --git a/timer/periodic_sampler/periodic_sampler.c b/timer/periodic_sampler/periodic_sampler.c
index b347855..b200c71 100644
--- a/timer/periodic_sampler/periodic_sampler.c
+++ b/timer/periodic_sampler/periodic_sampler.c
@@ -66,6 +66,7 @@ int main() {
 
     queue_free(&sample_fifo);
     printf("Done\n");
+    return 0;
 }
 
 bool timer_callback(repeating_timer_t *rt) {
diff --git a/uart/uart_advanced/uart_advanced.c b/uart/uart_advanced/uart_advanced.c
index c9b51d2..8bcf6c5 100644
--- a/uart/uart_advanced/uart_advanced.c
+++ b/uart/uart_advanced/uart_advanced.c
@@ -51,7 +51,7 @@ int main() {
     // Actually, we want a different speed
     // The call will return the actual baud rate selected, which will be as close as
     // possible to that requested
-    int actual = uart_set_baudrate(UART_ID, BAUD_RATE);
+    int __unused actual = uart_set_baudrate(UART_ID, BAUD_RATE);
 
     // Set UART flow control CTS/RTS, we don't want these, so turn them off
     uart_set_hw_flow(UART_ID, false, false);
diff --git a/usb/device/dev_hid_composite/dev_hid_composite.c b/usb/device/dev_hid_composite/dev_hid_composite.c
index 5f0ad1e..4578a00 100644
--- a/usb/device/dev_hid_composite/dev_hid_composite.c
+++ b/usb/device/dev_hid_composite/dev_hid_composite.c
@@ -134,7 +134,7 @@ void hid_task(void) {
         static bool has_key = false;
 
         static bool toggle = false;
-        if (toggle = !toggle) {
+        if ((toggle = !toggle)) {
             uint8_t keycode[6] = {0};
             keycode[0] = HID_KEY_A;
 
diff --git a/usb/device/dev_lowlevel/dev_lowlevel.c b/usb/device/dev_lowlevel/dev_lowlevel.c
index 2d4d55c..58a6924 100644
--- a/usb/device/dev_lowlevel/dev_lowlevel.c
+++ b/usb/device/dev_lowlevel/dev_lowlevel.c
@@ -113,7 +113,7 @@ struct usb_endpoint_configuration *usb_get_endpoint_configuration(uint8_t addr)
  */
 uint8_t usb_prepare_string_descriptor(const unsigned char *str) {
     // 2 for bLength + bDescriptorType + strlen * 2 because string is unicode. i.e. other byte will be 0
-    uint8_t bLength = 2 + (strlen(str) * 2);
+    uint8_t bLength = 2 + (strlen((const char *)str) * 2);
     static const uint8_t bDescriptorType = 0x03;
 
     volatile uint8_t *buf = &ep0_buf[0];
diff --git a/usb/device/dev_lowlevel/dev_lowlevel.h b/usb/device/dev_lowlevel/dev_lowlevel.h
index afe29cb..eef6540 100644
--- a/usb/device/dev_lowlevel/dev_lowlevel.h
+++ b/usb/device/dev_lowlevel/dev_lowlevel.h
@@ -129,8 +129,8 @@ static const unsigned char lang_descriptor[] = {
 };
 
 static const unsigned char *descriptor_strings[] = {
-        "Raspberry Pi",    // Vendor
-        "Pico Test Device" // Product
+        (unsigned char *) "Raspberry Pi",    // Vendor
+        (unsigned char *) "Pico Test Device" // Product
 };
 
 #endif
\ No newline at end of file