[PATCH v2 1/2] string: _FORTIFY_SOURCE=3 using __builtin_dynamic_object_size

[Florian Weimer]

* Siddhesh Poyarekar via Libc-alpha:

> On 12/14/20 8:24 PM, Florian Weimer via Libc-alpha wrote:
>> * Siddhesh Poyarekar via Libc-alpha:
>> 
>>> diff --git a/NEWS b/NEWS
>>> index 0820984547..4167f34c13 100644
>>> --- a/NEWS
>>> +++ b/NEWS
>>> @@ -28,6 +28,11 @@ Major new features:
>>>     The 32-bit RISC-V port requires at least Linux 5.4, GCC 7.1 and binutils
>>>     2.28.
>>>   +* A new fortification level _FORTIFY_SOURCE=3 is available.  At
>>> this level,
>>> +  glibc may use additional checks that may be computationally expensive.  At
>>> +  present these checks are available only on LLVM 9 and later.  The latest GCC
>>> +  available at this time (10.2) does not support this level of fortification.
>> I think it's still a fixed overhead per call (i.e., not proportional
>> to
>> buffer size or stack depth).  So the performance warning is perhaps a
>> bit too strong (likewise in the manual).
>
> How about:
>
> s/be computationally expensive/have a performance overhead/ ?
>
> I agree with Jakub that it's not fixed but I also agree that there's
> scope to soften "computationally expensive".

“have an additional performance overhead”?

Thanks,
Florian
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