lib: data-stack - fix pointer arithmetic compiler warning Clang's -fsanitize=unsigned-integer-overflow barfs as follows:
lib: data-stack - fix pointer arithmetic compiler warning
Clang's -fsanitize=unsigned-integer-overflow barfs as follows:

data-stack.c:477:29: runtime error: negation of 8 cannot be represented in type 'unsigned long'
data-stack.c:495:15: runtime error: negation of 8 cannot be represented in type 'unsigned long'

Which is of course complete bollocks. There is no 8, there's only an 8ul, and
the negation of 8ul is 0xfffffff8ul (or a wider equivalent). That's the law.

However, the pointer arithmetic which follows the negation, whilst almost
certainly working in practice, is probably bogus, so just make the thing
signed before the negation, and both problems go away.

Reported-by: Teemu Huovila <88ad39bd64f095dfd148c252c263bd192c832b17@dovecot.fi>
Signed-off-by: Phil Carmody <e888d2bd6f13f82caa51a37c03d034c76f661ba3@dovecot.fi>

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot