Re: [PATCH 11/11] cutils: Improve qemu_strtosz handling of fractions

[Eric Blake]

On Mon, May 08, 2023 at 03:03:43PM -0500, Eric Blake wrote:
> We have several limitations and bugs worth fixing; they are
> inter-related enough that it is not worth splitting this patch into
> smaller pieces:
> 
> * ".5k" should work to specify 512, just as "0.5k" does
> * "1.9999k" and "1." + "9"*50 + "k" should both produce the same
>   result of 2048 after rounding
> * "1." + "0"*350 + "1B" should not be treated the same as "1.0B";
>   underflow in the fraction should not be lost
> * "7.99e99" and "7.99e999" look similar, but our code was doing a
>   read-out-of-bounds on the latter because it was not expecting ERANGE
>   due to overflow. While we document that scientific notation is not
>   supported, and the previous patch actually fixed
>   qemu_strtod_finite() to no longer return ERANGE overflows, it is
>   easier to pre-filter than to try and determine after the fact if
>   strtod() consumed more than we wanted.  Note that this is a
>   low-level semantic change (when endptr is not NULL, we can now
>   successfully parse with a scale of 'E' and then report trailing
>   junk, instead of failing outright with EINVAL); but an earlier
>   commit already argued that this is not a high-level semantic change
>   since the only caller passing in a non-NULL endptr also checks that
>   the tail is whitespace-only.
> 
> Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1629

Also,

Fixes: cf923b78 ("utils: Improve qemu_strtosz() to have 64 bits of precision", 
6.0.0)
Fixes: 7625a1ed ("utils: Use fixed-point arithmetic in qemu_strtosz", 6.0.0)

> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  tests/unit/test-cutils.c | 51 +++++++++++------------
>  util/cutils.c            | 89 ++++++++++++++++++++++++++++------------
>  2 files changed, 88 insertions(+), 52 deletions(-)
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org