Re: [Qemu-devel] [PATCH v1 1/9] cutils: add qemu_strtod() and qemu_strtod_finite()

[Eric Blake <eblake@redhat.com>]

On 11/15/18 11:25 AM, David Hildenbrand wrote:

>> Also, just overflow.  Floating-point underflow is when a computation's
>> mathematical result is too close to zero to be represented without
>> extraordinary rounding error.
> 

>> works like qemu_strtoul().  I'd prefer longhand for qemu_strtod().  It
>> costs us a few lines, but it results in a clearer contract.
> 
> /**
>   * Convert string @nptr to a double.
>    *
>   * This is a wrapper around strtod() that is harder to misuse.
>   * Semantics of @nptr and @endptr match strtod() with differences
>   * noted below.
>   *
>   * @nptr may be null, and no conversion is performed then.
>   *
>   * If no conversion is performed, store @nptr in *@endptr and return
>   * -EINVAL.
>   *
>   * If @endptr is null, and the string isn't fully converted, return
>   * -EINVAL.  This is the case when the pointer that would be stored in
>   * a non-null @endptr points to a character other than '\0'.
>   *
>   * If the conversion overflows @result, store +/-HUGE_VAL, depending on
>   * the sign, in @result and return -ERANGE.

Fails to mention underflow. Maybe add:

If the conversion underflows, store +/-0.0 in @result, depending on the 
sign, and return -ERANGE.

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