Re: [PATCH v17 02/14] util/cutils: Use qemu_strtold_finite to parse size

[Markus Armbruster]

Tao Xu <address@hidden> writes:

> On 11/25/2019 2:56 PM, Markus Armbruster wrote:
>> Tao Xu <address@hidden> writes:
>>
>>> Support full 64bit precision, modify related test cases.
>>
>> That's not true in general: long double need not be any wider than
>> double.
>>
>> It might be true on the host machines we support, but I don't know.  If
>> we decide to rely on it, we better make the build fail when the host
>> machine doesn't meet our expectations, preferably in configure.
>>
> [...]
>>> -    if ((val * mul >= 0xfffffffffffffc00) || val < 0) {
>>> +    /* Values > UINT64_MAX overflow uint64_t */
>>> +    if ((val * mul > UINT64_MAX) || val < 0) {
>>>           retval = -ERANGE;
>>>           goto out;
>>>       }
>>
>> Not portable.  If it was, we'd have made this changd long ago :)
>>
>
> OK. So the suitable solution is what you suggested in v14?
>
> "A possible alternative is to parse the numeric part both as a double
> and as a 64 bit unsigned integer, then use whatever consumes more
> characters.  This enables providing full 64 bits unless you actually
> use
> a fraction."

Yes, that bypasses the portability issue.

> I will try this way.

Go ahead.