Re: [Qemu-devel] [PATCH v2 1/9] cutils: Add qemu_strtod() and qemu_strtod_finite()

[Markus Armbruster]

David Hildenbrand <address@hidden> writes:

> On 20.11.18 21:07, Markus Armbruster wrote:
>> Eric Blake <address@hidden> writes:
>> 
>>> On 11/20/18 3:25 AM, David Hildenbrand wrote:
>>>> Let's provide a wrapper for strtod().
>>>>
>>>> Reviewed-by: Eric Blake <address@hidden>
>>>
>>> This changed enough from v1 that I would have dropped R-b to ensure
>>> that reviewers notice the differences.
>
> Indeed, dropping it now ;)
>
>>>
>>>> Signed-off-by: David Hildenbrand <address@hidden>
>>>> ---
>>>>   include/qemu/cutils.h |  2 ++
>>>>   util/cutils.c         | 65 +++++++++++++++++++++++++++++++++++++++++++
>>>>   2 files changed, 67 insertions(+)
>>>>
>>>
>>>> + * If the conversion overflows, store +/-HUGE_VAL in @result, depending
>>>> + * on the sign, and return -ERANGE.
>>>> + *
>>>> + * If the conversion underflows, store ±0.0 in @result, depending on the
>>>> + * sign, and return -ERANGE.
>>>
>>> The use of UTF-8 ± in one place but not both is odd.  I think we're at
>>> the point where UTF-8 comments are acceptable these days, rather than
>>> trying to keep our codebase ASCII-clean, so I don't care which way you
>>> resolve the inconsistency.
>> 
>> 217 out of 6455 git-controlled files contain non-ASCII characters.  53
>> of them are binary, and don't count.  In most text files, it's for
>> spelling names of authors properly in comments.  Ample precedence for
>> UTF-8 in comments, I'd say.
>> 
>> That said, I second Eric's call for consistency, with the slightest of
>> preferrences for plain ASCII.
>
> I'll just go with +/-. Thanks.
>
>> 
>> I spotted UTF-8 in two error messages, which might still be unadvisable:
>> 
>> hw/misc/tmp105.c:        error_setg(errp, "value %" PRId64 ".%03" PRIu64 " 
>> °C is out of range",
>> hw/misc/tmp421.c:        error_setg(errp, "value %" PRId64 ".%03" PRIu64 " 
>> °C is out of range",
>> 
>>>> +/**
>>>> + * Convert string @nptr to a finite double.
>>>> + *
>>>> + * Works like qemu_strtod(), except that "NaN" and "inf" are rejected
>>>> + * with -EINVAL and no conversion is performed.
>>>> + */
>>>> +int qemu_strtod_finite(const char *nptr, const char **endptr, double 
>>>> *result)
>>>> +{
>>>> +    double tmp;
>>>> +    int ret;
>>>> +
>>>> +    ret = qemu_strtod(nptr, endptr, &tmp);
>>>> +    if (ret) {
>>>> +        return ret;
>>>
>>> So, if we overflow, we are returning -ERANGE but with nothing stored
>>> into *result.  This is different from qemu_strtod(), where a return of
>>> -ERANGE guarantees that *result is one of 4 values (+/- 0.0/inf).
>>> That seems awkward.
>> 
>> Violates the contract's "like qemu_strtod()".
>
> Right, I missed that. What about something like this:
>
> int qemu_strtod_finite(const char *nptr, const char **endptr, double
> *result)
> {
>     double tmp;
>     int ret;
>
>     ret = qemu_strtod(nptr, endptr, &tmp);
>     if (!ret && !isfinite(tmp)) {
>         if (endptr) {
>             *endptr = nptr;
>         }
>         ret = -EINVAL;
>     }
>
>     if (ret != -EINVAL) {
>         *result = tmp;
>     }
>     return ret;
> }

With these changes:
Reviewed-by: Markus Armbruster <address@hidden>