Re: [PATCH iproute2 v2] json_print: Fix hidden 64-bit type promotion

Stephen Hemminger
2018-04-25T14:55:30Z

On Wed, 25 Apr 2018 16:30:22 +0200
Toke Høiland-Jørgensen <toke@toke.dk> wrote:

> print_uint() will silently promote its variable type to uint64_t, but there
> is nothing that ensures that the format string specifier passed along with
> it fits (and the function name suggest to pass "%u").
>
> Fix this by changing print_uint() to use a native 'unsigned int' type, and
> introduce a separate print_u64() function for printing 64-bit values. All
> call sites that were actually printing 64-bit values using print_uint() are
> converted to use print_u64() instead.
>
> Since print_int() was already using native int types, just add a
> print_s64() to match, but don't convert any call sites.
>
> Cc: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

Yes, this makes sense. Maybe there should be a print_luint for consistency.
Also, I tried (in vain) to make a version that allows GCC to check the
format string. But it was a struggle and just gave up.