Re: [PATCH] Add _FORTIFY_SOURCE implementation documentation [BZ #28998]

[Jeff Law <jeffreyalaw@gmail.com>]

On 1/3/23 07:43, Siddhesh Poyarekar via Libc-alpha wrote:
> On 2022-12-22 08:08, Sam James wrote:
>>
>>
>>> On 22 Dec 2022, at 12:56, Siddhesh Poyarekar <siddhesh@gotplt.org> 
>>> wrote:
>>>
>>> Ping!  Any further comments other than the redundant 'See' Andreas 
>>> noted?
>>>
>>
>> It looks good & thanks for doing it.
>>
>> I wonder if it's worth noting (maybe it's obvious) that tools which
>> make use of LD_PRELOAD may need to provide their own wrappers.
>>
>> (umockdev being an example I'm thinking of here.)
> 
> Hi Sam, sorry I missed your response (and funnily, I got 3 of them!).
> 
> I'm not sure, there are other issues with interposing, e.g. string 
> function calls where the result is already dependent on how the compiler 
> treats those calls, making the result of the interposition kinda 
> indeterminate across builds.  So I don't know how useful it would be to 
> call it out specifically in the context of _FORTIFY_SOURCE.  However, I 
> don't think it's a bad idea to do so either (i.e. I don't see it 
> imposing any constraints on us as implementers), so if you like it (and 
> others don't express a dislike), I'll be happy to add a note in there.
Right.  In general the compiler may replace a variety of library calls 
with inline versions.  The set of calls subject to this behavior isn't 
stable across compiler versions, targets or even across different call 
sites as the call site context may affect if the compiler thinks 
inlining is profitable or not.

jeff