nayuta-yanagisawa reported that the test mariabackup.huge_lsn,strict_full_crc32 would occasionally trigger AddressSanitizer heap-buffer-overflow on his system.
The following patch fixes it:
In this test, some Perl code generates always the same log file that would wrap around at the end of the file. The recv_sys.offset will be equal to recv_sys.len, that is, b is pointing just past the end of log_sys.buf. We are actually only interested in the value of the byte (the first byte of the parsed record) at that offset if r == recv_sys_t::OK, which indicates that the entire mini-transaction was present in the buffer.
I do not think that this bug has much practical impact outside AddressSanitizer.