On Tue, 16 Aug 2016, Ed Schouten wrote:
Hi Emmanuel,
Log:
Use %ju modifier for u_int64_t and %jd modifier for off_t.
off_t is long long on arm32 and long on amd64
I think both of these should be solved differently:
- For uint64_t, you can use <inttypes.h>'s PRIu64 in the formatting
string. In kernel space, I suspect you need to use something like
<machine/inttypes.h>.
Ugh.
- For off_t, it's all right to print it with %jd, but then be sure to
also add a cast to the argument itself. It may not necessarily be
equal to an intmax_t.
This shows how stupid the PRI* macros are. They might be available for
0.1% of typedefed types in a medium-sized source tree. But to use them,
you have to know their exact type, and change all printfs using them
whenever the typedef is changed. If it is changed to a non-fixed width
type, then the printfs need lots of editing to change to a cast. Their
only advantage is that they are more space and time efficient, especially
on 16-bit systems.
Extensive use of fixed-width type is another bug. It asks for a fixed
ABI at any cost to efficiency or space. FreeBSD almost never uses
"fast" or "least" integer types. However, if you use these types, there
are PRI* mistakes for them too.
The SCN* macros are not quite as stupid as PRI*, but they should never
be used. scanf() is already unusable since it gives undefined
behaviour on overflow. These macros are not quite as stupid as PRI*
since casts don't work so well for input. The corrsponding thing is
to scan input into variables of type [u]intmax_t and convert to the
corresponding type, of course without any bounds checking so that
you get similar undefined behaviour on overflow as when using SCN*.
Bruce
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