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

[Siddhesh Poyarekar]

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".

Siddhesh