With matched-but-unaligned address/data residues the byte-wise prefix
leaves i % 4 != 0, so dst[i >> 2] stored the word below the intended
address, dropped the tail bytes of the unit, and issued an unaligned
NVM store (HardFault on M0+). Derive src/dst from address + i, matching
the already-correct else branch.
Verification: new matched-alignment test fails pre-fix in both
unit-flash-write-samr21 and unit-flash-write-same51 (tail bytes stay
0xFF), 3/3 post-fix; full make -C tools/unit-tests run green.
In the else branch of hal_flash_write, off was computed once per call from
the original (call-time) "address" instead of the current position
"address + i". The word index dst_idx advanced with i, but the fill loop
kept starting at the stale off, so once destination address and source
buffer had different alignment mod 4, every word after the first was
filled at the wrong byte offset, dropping and misplacing data. Derive off
and dst from address + i so each word's offset tracks the current
position, mirroring the fix already applied to mcxa.c for the same bug
class (F-5963).
Daniele Lacamera
David Garske
gojimmypi
Daniele Lacamera