diff --git a/boards/cc2650stk/doc.txt b/boards/cc2650stk/doc.txt
index 1f3f50d4b638..eb74a39560dc 100644
--- a/boards/cc2650stk/doc.txt
+++ b/boards/cc2650stk/doc.txt
@@ -127,7 +127,9 @@ advertising channels, as well as the corresponding variables in the RIOT
 command.
 
 ```
-typedef struct __attribute__ ((aligned(4))) {
+#include <stdalign.h>
+
+typedef struct alignas(4) {
     radio_op_command_t ropCmd;
     uint8_t channel;
     struct {
diff --git a/core/lib/include/xfa.h b/core/lib/include/xfa.h
index e18196ff788b..06cc1693a3db 100644
--- a/core/lib/include/xfa.h
+++ b/core/lib/include/xfa.h
@@ -26,6 +26,8 @@
 #define XFA_H
 
 #include <inttypes.h>
+#include <stdalign.h>
+
 #include "compiler_hints.h"
 
 /*
@@ -45,7 +47,7 @@ _Pragma("GCC diagnostic ignored \"-Warray-bounds\"")
  */
 #define _XFA(type, name, prio) \
     NO_SANITIZE_ARRAY \
-    __attribute__((used, section(".xfa." #name "." #prio))) _Alignas(type) type
+    __attribute__((used, section(".xfa." #name "." #prio))) alignas(type) type
 
 /**
  * @brief helper macro for other XFA_* macros
@@ -54,7 +56,7 @@ _Pragma("GCC diagnostic ignored \"-Warray-bounds\"")
  */
 #define _XFA_CONST(type, name, prio) \
     NO_SANITIZE_ARRAY \
-    __attribute__((used, section(".roxfa." #name "." #prio))) _Alignas(type) type
+    __attribute__((used, section(".roxfa." #name "." #prio))) alignas(type) type
 
 /**
  * @brief Define a read-only cross-file array
diff --git a/cpu/arm7_common/arm_cpu.c b/cpu/arm7_common/arm_cpu.c
index 16343499560c..f1b91b0a3a52 100644
--- a/cpu/arm7_common/arm_cpu.c
+++ b/cpu/arm7_common/arm_cpu.c
@@ -16,8 +16,10 @@
  * @}
  */
 
+#include <stdalign.h>
 #include <stdint.h>
 #include <stdio.h>
+
 #include "arm_cpu.h"
 #include "irq.h"
 #include "sched.h"
@@ -26,12 +28,12 @@
 #define STACK_MARKER    (0x77777777)
 #define REGISTER_CNT    (12)
 
-__attribute__((used, section(".usr_stack"), aligned(4))) uint8_t usr_stack[USR_STACKSIZE];
-__attribute__((used, section(".und_stack"), aligned(4))) uint8_t und_stack[UND_STACKSIZE];
-__attribute__((used, section(".fiq_stack"), aligned(4))) uint8_t fiq_stack[FIQ_STACKSIZE];
-__attribute__((used, section(".irq_stack"), aligned(4))) uint8_t irq_stack[ISR_STACKSIZE];
-__attribute__((used, section(".abt_stack"), aligned(4))) uint8_t abt_stack[ABT_STACKSIZE];
-__attribute__((used, section(".svc_stack"), aligned(4))) uint8_t svc_stack[ISR_STACKSIZE];
+__attribute__((used, section(".usr_stack"))) alignas(4) uint8_t usr_stack[USR_STACKSIZE];
+__attribute__((used, section(".und_stack"))) alignas(4) uint8_t und_stack[UND_STACKSIZE];
+__attribute__((used, section(".fiq_stack"))) alignas(4) uint8_t fiq_stack[FIQ_STACKSIZE];
+__attribute__((used, section(".irq_stack"))) alignas(4) uint8_t irq_stack[ISR_STACKSIZE];
+__attribute__((used, section(".abt_stack"))) alignas(4) uint8_t abt_stack[ABT_STACKSIZE];
+__attribute__((used, section(".svc_stack"))) alignas(4) uint8_t svc_stack[ISR_STACKSIZE];
 
 #if (ISR_STACKSIZE % 4)
 #error "ISR_STACKSIZE must be a multiple of 4"
diff --git a/cpu/esp32/include/periph_cpu.h b/cpu/esp32/include/periph_cpu.h
index 6bd48fd821b7..d27d3191dc6a 100644
--- a/cpu/esp32/include/periph_cpu.h
+++ b/cpu/esp32/include/periph_cpu.h
@@ -19,6 +19,7 @@
 #ifndef PERIPH_CPU_H
 #define PERIPH_CPU_H
 
+#include <stdalign.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include "sdkconfig.h"
@@ -726,7 +727,7 @@ typedef struct {
 /**
  * @brief  SDIO/SDMMC buffer instantiation requirement for SDHC
  */
-#define SDMMC_CPU_DMA_REQUIREMENTS  __attribute__((aligned(SDMMC_CPU_DMA_ALIGNMENT)))
+#define SDMMC_CPU_DMA_REQUIREMENTS  alignas(SDMMC_CPU_DMA_ALIGNMENT)
 
 /**
  * @brief  SDIO/SDMMC buffer alignment for SDHC because of DMA/FIFO buffer restrictions
diff --git a/cpu/native/periph/flashpage.c b/cpu/native/periph/flashpage.c
index 8da0c26a8ea7..19e6561a62dd 100644
--- a/cpu/native/periph/flashpage.c
+++ b/cpu/native/periph/flashpage.c
@@ -19,6 +19,7 @@
  */
 
 #include <assert.h>
+#include <stdalign.h>
 #include <string.h>
 
 #include "cpu.h"
@@ -27,7 +28,7 @@
 #define ENABLE_DEBUG 0
 #include "debug.h"
 
-__attribute__((aligned(FLASHPAGE_SIZE * FLASHPAGE_NUMOF)))
+alignas(FLASHPAGE_SIZE * FLASHPAGE_NUMOF)
 char _native_flash[FLASHPAGE_SIZE * FLASHPAGE_NUMOF];
 
 void flashpage_erase(unsigned page)
diff --git a/cpu/nrf5x_common/include/periph_cpu_common.h b/cpu/nrf5x_common/include/periph_cpu_common.h
index b37a4a8b1da2..b0f6d9d7163d 100644
--- a/cpu/nrf5x_common/include/periph_cpu_common.h
+++ b/cpu/nrf5x_common/include/periph_cpu_common.h
@@ -417,7 +417,7 @@ typedef struct {
 /**
  * @brief USBDEV buffer instantiation requirement
  */
-#define USBDEV_CPU_DMA_REQUIREMENTS    __attribute__((aligned(USBDEV_CPU_DMA_ALIGNMENT)))
+#define USBDEV_CPU_DMA_REQUIREMENTS    alignas(USBDEV_CPU_DMA_ALIGNMENT)
 
 #if !defined(CPU_FAM_NRF51) && !defined(DOXYGEN)
 /**
diff --git a/cpu/riscv_common/irq_arch.c b/cpu/riscv_common/irq_arch.c
index f37b58e55050..dd73f3f38907 100644
--- a/cpu/riscv_common/irq_arch.c
+++ b/cpu/riscv_common/irq_arch.c
@@ -18,8 +18,9 @@
  * @}
  */
 
-#include <stdio.h>
 #include <inttypes.h>
+#include <stdalign.h>
+#include <stdio.h>
 
 #include "macros/xtstr.h"
 #include "cpu.h"
@@ -160,7 +161,7 @@ static void handle_trap(uword_t mcause)
 /* Marking this as interrupt to ensure an mret at the end, provided by the
  * compiler. Aligned to 64-byte boundary as per RISC-V spec and required by some
  * of the supported platforms (gd32)*/
-__attribute((aligned(64)))
+alignas(64)
 static void __attribute__((interrupt)) trap_entry(void)
 {
     __asm__ volatile (
diff --git a/cpu/sam0_common/include/periph_cpu_common.h b/cpu/sam0_common/include/periph_cpu_common.h
index dd8be928de9a..1093bb6cc58e 100644
--- a/cpu/sam0_common/include/periph_cpu_common.h
+++ b/cpu/sam0_common/include/periph_cpu_common.h
@@ -21,6 +21,8 @@
 #ifndef PERIPH_CPU_COMMON_H
 #define PERIPH_CPU_COMMON_H
 
+#include <stdalign.h>
+
 #include "cpu.h"
 #include "exti_config.h"
 #include "timer_config.h"
@@ -992,7 +994,7 @@ typedef struct {
 /**
  * @brief USBDEV buffer instantiation requirement
  */
-#define USBDEV_CPU_DMA_REQUIREMENTS    __attribute__((aligned(USBDEV_CPU_DMA_ALIGNMENT)))
+#define USBDEV_CPU_DMA_REQUIREMENTS    alignas(USBDEV_CPU_DMA_ALIGNMENT)
 
 /**
  * @brief USB peripheral parameters
@@ -1015,7 +1017,7 @@ typedef struct {
 /**
  * @brief SDIO/SDMMC buffer instantiation requirement for SDHC
  */
-#define SDMMC_CPU_DMA_REQUIREMENTS  __attribute__((aligned(SDMMC_CPU_DMA_ALIGNMENT)))
+#define SDMMC_CPU_DMA_REQUIREMENTS  alignas(SDMMC_CPU_DMA_ALIGNMENT)
 
 /**
  * @brief SDHC peripheral configuration
diff --git a/cpu/sam0_common/periph/eth.c b/cpu/sam0_common/periph/eth.c
index f2f54982f5cb..313509ef77eb 100644
--- a/cpu/sam0_common/periph/eth.c
+++ b/cpu/sam0_common/periph/eth.c
@@ -78,8 +78,8 @@ struct eth_buf_desc {
 /* GMAC buffer descriptors */
 #define GMAC_DESC_ALIGNMENT 8
 #define GMAC_BUF_ALIGNMENT  32
-static struct eth_buf_desc rx_desc[ETH_RX_BUFFER_COUNT] __attribute__((aligned(GMAC_DESC_ALIGNMENT)));
-static struct eth_buf_desc tx_desc[ETH_TX_BUFFER_COUNT] __attribute__((aligned(GMAC_DESC_ALIGNMENT)));
+static alignas(GMAC_DESC_ALIGNMENT) struct eth_buf_desc rx_desc[ETH_RX_BUFFER_COUNT];
+static alignas(GMAC_DESC_ALIGNMENT) struct eth_buf_desc tx_desc[ETH_TX_BUFFER_COUNT];
 
 static struct eth_buf_desc *rx_curr;
 static struct eth_buf_desc *tx_curr;
@@ -89,8 +89,8 @@ static struct eth_buf_desc *tx_curr;
 static uint8_t  tx_idx;
 static uint8_t  rx_idx;
 
-static uint8_t  rx_buf[ETH_RX_BUFFER_COUNT][ETH_RX_BUFFER_SIZE] __attribute__((aligned(GMAC_BUF_ALIGNMENT)));
-static uint8_t  tx_buf[ETH_TX_BUFFER_COUNT][ETH_TX_BUFFER_SIZE] __attribute__((aligned(GMAC_BUF_ALIGNMENT)));
+static alignas(GMAC_BUF_ALIGNMENT) uint8_t  rx_buf[ETH_RX_BUFFER_COUNT][ETH_RX_BUFFER_SIZE];
+static alignas(GMAC_BUF_ALIGNMENT) uint8_t  tx_buf[ETH_TX_BUFFER_COUNT][ETH_TX_BUFFER_SIZE];
 extern sam0_eth_netdev_t _sam0_eth_dev;
 
 static bool _is_sleeping;
diff --git a/cpu/stm32/include/periph/cpu_sdmmc.h b/cpu/stm32/include/periph/cpu_sdmmc.h
index 4048c55655b6..1f8fcb67bc38 100644
--- a/cpu/stm32/include/periph/cpu_sdmmc.h
+++ b/cpu/stm32/include/periph/cpu_sdmmc.h
@@ -19,6 +19,7 @@
 #ifndef PERIPH_CPU_SDMMC_H
 #define PERIPH_CPU_SDMMC_H
 
+#include <stdalign.h>
 #include <stdint.h>
 
 #include "periph/cpu_dma.h"
@@ -45,7 +46,7 @@ extern "C" {
 /**
  * @brief SDIO/SDMMC buffer instantiation requirement for STM32
  */
-#define SDMMC_CPU_DMA_REQUIREMENTS  __attribute__((aligned(SDMMC_CPU_DMA_ALIGNMENT)))
+#define SDMMC_CPU_DMA_REQUIREMENTS  alignas(SDMMC_CPU_DMA_ALIGNMENT)
 
 /**
  * @brief SDIO/SDMMC pin structure for STM32
diff --git a/cpu/stm32/include/periph/cpu_usbdev.h b/cpu/stm32/include/periph/cpu_usbdev.h
index bd978c9422f5..e6d34320b256 100644
--- a/cpu/stm32/include/periph/cpu_usbdev.h
+++ b/cpu/stm32/include/periph/cpu_usbdev.h
@@ -21,6 +21,7 @@
 #ifndef PERIPH_CPU_USBDEV_H
 #define PERIPH_CPU_USBDEV_H
 
+#include <stdalign.h>
 #include <stdint.h>
 
 #include "periph/cpu_gpio.h"
@@ -37,7 +38,7 @@ extern "C" {
 /**
  * @brief USBDEV buffer instantiation requirement
  */
-#define USBDEV_CPU_DMA_REQUIREMENTS    __attribute__((aligned(USBDEV_CPU_DMA_ALIGNMENT)))
+#define USBDEV_CPU_DMA_REQUIREMENTS    alignas(USBDEV_CPU_DMA_ALIGNMENT)
 
 /**
  * @brief stm32 USB device FS configuration
diff --git a/drivers/include/periph/flashpage.h b/drivers/include/periph/flashpage.h
index a2c8908d087f..af95b3daf242 100644
--- a/drivers/include/periph/flashpage.h
+++ b/drivers/include/periph/flashpage.h
@@ -48,6 +48,7 @@
 #ifndef PERIPH_FLASHPAGE_H
 #define PERIPH_FLASHPAGE_H
 
+#include <stdalign.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -171,7 +172,7 @@ enum {
  * @param[in] size size of the array in unit of @ref FLASHPAGE_SIZE
  */
 #define FLASH_WRITABLE_INIT(name, size) \
-    __attribute__((aligned(FLASHPAGE_SIZE))) \
+    alignas(FLASHPAGE_SIZE) \
     __attribute__((section(".flash_writable." #name))) \
     static const uint8_t name [size * FLASHPAGE_SIZE]
 #endif
diff --git a/drivers/mtd_flashpage/mtd_flashpage.c b/drivers/mtd_flashpage/mtd_flashpage.c
index 426927c3f3d3..1356c1bd0efd 100644
--- a/drivers/mtd_flashpage/mtd_flashpage.c
+++ b/drivers/mtd_flashpage/mtd_flashpage.c
@@ -21,9 +21,10 @@
  * @}
  */
 
-#include <string.h>
-#include <errno.h>
 #include <assert.h>
+#include <errno.h>
+#include <stdalign.h>
+#include <string.h>
 
 #include "architecture.h"
 #include "cpu.h"
@@ -114,8 +115,7 @@ static int _write_page(mtd_dev_t *dev, const void *buf, uint32_t page, uint32_t
 
     if ((addr % FLASHPAGE_WRITE_BLOCK_ALIGNMENT) || (size < FLASHPAGE_WRITE_BLOCK_SIZE) ||
         ((uintptr_t)buf % FLASHPAGE_WRITE_BLOCK_ALIGNMENT)) {
-        uint8_t tmp[FLASHPAGE_WRITE_BLOCK_SIZE]
-                __attribute__ ((aligned (FLASHPAGE_WRITE_BLOCK_ALIGNMENT)));
+        uint8_t alignas(FLASHPAGE_WRITE_BLOCK_ALIGNMENT) tmp[FLASHPAGE_WRITE_BLOCK_SIZE];
 
         offset = addr % FLASHPAGE_WRITE_BLOCK_ALIGNMENT;
         size = MIN(size, FLASHPAGE_WRITE_BLOCK_SIZE - offset);
diff --git a/examples/lua_REPL/main.c b/examples/lua_REPL/main.c
index 361d726300cc..8145b7eb8024 100644
--- a/examples/lua_REPL/main.c
+++ b/examples/lua_REPL/main.c
@@ -18,6 +18,7 @@
  * @}
  */
 
+#include <stdalign.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -31,7 +32,7 @@
  */
 #define MAIN_LUA_MEM_SIZE (40000)
 
-static char lua_memory[MAIN_LUA_MEM_SIZE] __attribute__ ((aligned(__BIGGEST_ALIGNMENT__)));
+static alignas(__BIGGEST_ALIGNMENT__) char lua_memory[MAIN_LUA_MEM_SIZE];
 
 #define BARE_MINIMUM_MODS (LUAR_LOAD_BASE | LUAR_LOAD_IO | LUAR_LOAD_CORO | LUAR_LOAD_PACKAGE)
 
diff --git a/examples/lua_basic/main.c b/examples/lua_basic/main.c
index ba1ba378259d..1e8dca678fb2 100644
--- a/examples/lua_basic/main.c
+++ b/examples/lua_basic/main.c
@@ -18,6 +18,7 @@
  * @}
  */
 
+#include <stdalign.h>
 #include <stdio.h>
 #include <errno.h>
 
@@ -32,7 +33,7 @@
 #else
 #define LUA_MEM_SIZE (11000)
 #endif
-static char lua_mem[LUA_MEM_SIZE] __attribute__ ((aligned(__BIGGEST_ALIGNMENT__)));
+static alignas(__BIGGEST_ALIGNMENT__) char lua_mem[LUA_MEM_SIZE];
 
 int lua_run_script(const uint8_t *buffer, size_t buffer_len)
 {
diff --git a/sys/include/architecture.h b/sys/include/architecture.h
index 37c36a7a32d6..34081e1bbba3 100644
--- a/sys/include/architecture.h
+++ b/sys/include/architecture.h
@@ -24,9 +24,10 @@
 #ifndef ARCHITECTURE_H
 #define ARCHITECTURE_H
 
-#include <stdint.h>
 #include <inttypes.h>
 #include <limits.h>
+#include <stdalign.h>
+#include <stdint.h>
 
 #include "architecture_arch.h" /* IWYU pragma: export */
 
@@ -203,7 +204,7 @@ typedef uintptr_t   uinttxtptr_t;
  * char WORD_ALIGNED thread_stack[THREAD_STACKSIZE_DEFAULT];
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  */
-#define WORD_ALIGNED __attribute__((aligned(ARCHITECTURE_WORD_BYTES)))
+#define WORD_ALIGNED alignas(ARCHITECTURE_WORD_BYTES)
 
 /**
  * @brief       Check if @p addr is alignment to @p alignment
diff --git a/sys/include/can/can.h b/sys/include/can/can.h
index b0974aa743fb..a071399bf412 100644
--- a/sys/include/can/can.h
+++ b/sys/include/can/can.h
@@ -26,12 +26,13 @@
 #ifndef CAN_CAN_H
 #define CAN_CAN_H
 
+#include <stdalign.h>
+#include <stdint.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <stdint.h>
-
 #if defined(__linux__)
 
 #include <linux/can.h>
@@ -92,7 +93,7 @@ struct can_frame {
     uint8_t __res0;  /**< reserved / padding */
     uint8_t __res1;  /**< reserved / padding */
     /** Frame data */
-    uint8_t data[CAN_MAX_DLEN] __attribute__((aligned(8)));
+    uint8_t alignas(8) data[CAN_MAX_DLEN];
 };
 
 /**
diff --git a/sys/include/event.h b/sys/include/event.h
index 19daf5c2091b..6015a5d3da9e 100644
--- a/sys/include/event.h
+++ b/sys/include/event.h
@@ -153,7 +153,8 @@ struct event {
 /**
  * @brief   event queue structure
  */
-typedef struct PTRTAG {
+typedef struct {
+    PTRTAG
     clist_node_t event_list;    /**< list of queued events              */
     thread_t *waiter;           /**< thread owning event queue          */
 } event_queue_t;
diff --git a/sys/include/pm_layered.h b/sys/include/pm_layered.h
index f0c2236654cd..397e5221b05c 100644
--- a/sys/include/pm_layered.h
+++ b/sys/include/pm_layered.h
@@ -55,8 +55,9 @@ extern "C" {
  * @brief Power Management mode blocker typedef
  */
 typedef struct {
+    WORD_ALIGNED
     uint8_t blockers[PM_NUM_MODES];     /**< number of blockers for the mode */
-} WORD_ALIGNED pm_blocker_t;
+} pm_blocker_t;
 
 /**
  * @brief   Block a power mode
diff --git a/sys/include/ptrtag.h b/sys/include/ptrtag.h
index 187477b2f91d..c93f0f77ba60 100644
--- a/sys/include/ptrtag.h
+++ b/sys/include/ptrtag.h
@@ -63,6 +63,7 @@
 
 #include <assert.h>
 #include <inttypes.h>
+#include <stdalign.h>
 #include <stdint.h>
 
 #ifdef __cplusplus
@@ -74,7 +75,7 @@ extern "C" {
  *
  * @details This will ensure a minimum alignment of 4 bytes
  */
-#define PTRTAG  __attribute__((aligned(4)))
+#define PTRTAG  alignas(4)
 
 /**
  * @brief   Create a tagged pointer
diff --git a/sys/include/riotboot/flashwrite.h b/sys/include/riotboot/flashwrite.h
index c76a7b2dc3cb..43cc424ba3c6 100644
--- a/sys/include/riotboot/flashwrite.h
+++ b/sys/include/riotboot/flashwrite.h
@@ -59,6 +59,8 @@
 #ifndef RIOTBOOT_FLASHWRITE_H
 #define RIOTBOOT_FLASHWRITE_H
 
+#include <stdalign.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -94,7 +96,7 @@ extern "C" {
  * @brief Extra attributes required for the firmware intermediate buffer
  */
 #define RIOTBOOT_FLASHPAGE_BUFFER_ATTRS \
-    __attribute__((aligned(FLASHPAGE_WRITE_BLOCK_ALIGNMENT)))
+    alignas(FLASHPAGE_WRITE_BLOCK_ALIGNMENT)
 
 /**
  * @brief   firmware update state structure
diff --git a/sys/riotboot/serial.c b/sys/riotboot/serial.c
index ae6f57808861..f744cc2848f3 100644
--- a/sys/riotboot/serial.c
+++ b/sys/riotboot/serial.c
@@ -19,6 +19,7 @@
  */
 
 #include <assert.h>
+#include <stdalign.h>
 #include <string.h>
 
 #include "stdio_uart.h"
@@ -109,8 +110,7 @@ static bool _bootdelay(unsigned tries, volatile bool *boot_default)
     return *boot_default;
 }
 
-__attribute__ ((aligned(4)))
-static struct {
+static alignas(4) struct {
     uint8_t pos;                /* current pos in rx buffer */
     uint8_t remaining;          /* remaining bytes to read  */
     union {
diff --git a/tests/drivers/mtd_flashpage/main.c b/tests/drivers/mtd_flashpage/main.c
index 96957ca67bb9..56d05419babd 100644
--- a/tests/drivers/mtd_flashpage/main.c
+++ b/tests/drivers/mtd_flashpage/main.c
@@ -11,6 +11,7 @@
  *
  * @file
  */
+#include <stdalign.h>
 #include <stdbool.h>
 #include <string.h>
 #include <errno.h>
@@ -118,8 +119,7 @@ static void test_mtd_write_erase(void)
 
 static void test_mtd_write_read(void)
 {
-    const char buf[] __attribute__ ((aligned (FLASHPAGE_WRITE_BLOCK_ALIGNMENT)))
-            = "ABCDEFGHIJKLMNO";
+    const alignas(FLASHPAGE_WRITE_BLOCK_ALIGNMENT) char buf[] = "ABCDEFGHIJKLMNO";
 
     uint8_t buf_empty[3];
     memset(buf_empty, FLASHPAGE_ERASE_STATE, sizeof(buf_empty));
diff --git a/tests/periph/flashpage/main.c b/tests/periph/flashpage/main.c
index 738bd1653213..45bb3a694df0 100644
--- a/tests/periph/flashpage/main.c
+++ b/tests/periph/flashpage/main.c
@@ -18,12 +18,12 @@
  * @}
  */
 
-#include <assert.h>
+#include <ctype.h>
 #include <inttypes.h>
+#include <stdalign.h>
 #include <stdio.h>
-#include <string.h>
 #include <stdlib.h>
-#include <ctype.h>
+#include <string.h>
 
 #include "architecture.h"
 #include "od.h"
@@ -43,7 +43,7 @@
 #endif
 
 /* When writing raw bytes on flash, data must be correctly aligned. */
-#define ALIGNMENT_ATTR __attribute__((aligned(FLASHPAGE_WRITE_BLOCK_ALIGNMENT)))
+#define ALIGNMENT_ATTR alignas(FLASHPAGE_WRITE_BLOCK_ALIGNMENT)
 
 /* We must not write chunks smaller than FLASHPAGE_WRITE_BLOCK_SIZE */
 #if FLASHPAGE_WRITE_BLOCK_SIZE > 64
@@ -55,7 +55,7 @@
 /*
  * @brief   Allocate an aligned buffer for raw writings
  */
-static uint8_t raw_buf[RAW_BUF_SIZE] ALIGNMENT_ATTR;
+static ALIGNMENT_ATTR uint8_t raw_buf[RAW_BUF_SIZE];
 
 #ifdef MODULE_PERIPH_FLASHPAGE_PAGEWISE
 /**
@@ -66,7 +66,7 @@ static uint8_t raw_buf[RAW_BUF_SIZE] ALIGNMENT_ATTR;
  *          32 bit alignment implicitly and there are cases (stm32l4) that
  *          requires 64 bit alignment.
  */
-static uint8_t page_mem[FLASHPAGE_SIZE] ALIGNMENT_ATTR;
+static ALIGNMENT_ATTR uint8_t page_mem[FLASHPAGE_SIZE];
 
 #ifdef MODULE_PERIPH_FLASHPAGE_IN_ADDRESS_SPACE
 /**
diff --git a/tests/pkg/lua_loader/main.c b/tests/pkg/lua_loader/main.c
index 889546bcc44f..2fa96dc8b289 100644
--- a/tests/pkg/lua_loader/main.c
+++ b/tests/pkg/lua_loader/main.c
@@ -25,6 +25,7 @@
  */
 
 #include <stdio.h>
+#include <stdalign.h>
 #include <string.h>
 
 #include "lua_run.h"
@@ -74,7 +75,7 @@ const size_t lua_riot_builtin_c_table_len =
 #else
 #define LUA_MEM_SIZE (11000)
 #endif
-static char lua_mem[LUA_MEM_SIZE] __attribute__ ((aligned(__BIGGEST_ALIGNMENT__)));
+static alignas(__BIGGEST_ALIGNMENT__) char lua_mem[LUA_MEM_SIZE];
 
 #define LINEBUF_SZ (32)
 static char linebuf[LINEBUF_SZ];
diff --git a/tests/sys/ptrtag/main.c b/tests/sys/ptrtag/main.c
index ab157b7b6e85..38dfabf03e29 100644
--- a/tests/sys/ptrtag/main.c
+++ b/tests/sys/ptrtag/main.c
@@ -25,7 +25,8 @@
 #include "ptrtag.h"
 #include "test_utils/expect.h"
 
-typedef struct PTRTAG {
+typedef struct {
+    PTRTAG
     uint8_t a;
 } custom_type_t;