[riot-notifications] [RIOT-OS/RIOT] sam0_common/periph/flashpage: fix unaligned write (#15707)

Marian Buschsieweke notifications at github.com
Mon Jan 18 18:01:49 CET 2021

@maribu commented on this pull request.

> @@ -223,21 +230,25 @@ static void _write_page(void* dst, const void *data, size_t len, void (*cmd_writ
     /* write the first, unaligned bytes */
-    if (unaligned_start) {
-        *dst32++ = unaligned_pad_start(data, unaligned_start);
-        data = (uint8_t*)data + unaligned_start;
+    if (len_unaligned_start) {
+        *dst32++ = unaligned_pad_start(data, len_unaligned_start,
+                offset_unaligned_start);
+        data = (uint8_t*)data + len_unaligned_start;
     /* copy whole words */
     const uint32_t *data32 = data;

An `uint32_t *` should always be aligned to 4 byte to avoid confusion. I'm aware that `unaligned_get_u32()` is used to access data at this address, which is correct. But the pointer type should `uint8_t *` or `void *`, if you're not sure about the alignment. I'm aware that `dst32++` is more readable than `dst32 += sizeof(uint32_t)` (when `uint8_t *` is used) or even `dst32 = (uintptr_t)dst32 + sizeof(uint32_t)` (when `void *` is used). But otherwise this is undefined behavior.

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