[wwwdocs] List -Wabsolute-value in gcc-9/changes.html
Martin Sebor
msebor@gmail.com
Mon Jan 28 19:02:00 GMT 2019
On 1/26/19 3:37 PM, Martin Jambor wrote:
> Hi,
>
> On Sat, Jan 26 2019, Gerald Pfeifer wrote:
>> On Sat, 26 Jan 2019, Martin Jambor wrote:
>>> I'd like to propose the following hunk mentioning -Wabsolute-value in
>>> changes.html of the upcoming gcc 9. Is it OK?
>>
>> Lovely^WThanks, ok!
>>
>> Actually, one question:
>>
>>> + <li><code>-Wabsolute-value</code> warns when a wrong absolute value
>>> + function seems to be used or when it does not have any effect because
>>> + its argument is an unsigned type. The <code>-Wabsolute-value</code>
>>> + option is included in <code>-Wextra</code>.
>>
>> What is a "wrong absolute value function"? That might be good to
>> show by means of an example? (Also in invoke.texi, which I checked
>> before writing this.)
>
> Most usually wrong means an absolute value function for a shorter type
> than the one privided, such as abs when labs would be approproiate, or
> abs or labs when you actually need llabs. Or using normal
> floating-point absolute value function such as fabs for
> binary-coded-decimal. Or even for a complex double/float, which
> hitherto passed without a warning.
>
> I'm not sure how to change the wording, perhaps "...when a used absolute
> value function seems wrong for the type of its argument" ...?
Would this work?
-Wabsolute-value warns for calls to standard functions that compute
the absolute value of an argument when a more appropriate standard
function is available. For example, calling abs(3.14) triggers
the warning because the appropriate function to call to compute
the absolute value of a double argument is fabs. The option also
triggers warnings when the argument in a call to such a function
has an unsigned type.
Martin
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