asprintf() issue

[Michael Kerrisk (man-pages)]

On 05/14/2015 07:30 AM, Carlos O'Donell wrote:
> On 05/13/2015 01:24 PM, Joseph Myers wrote:
>> On Wed, 13 May 2015, Carlos O'Donell wrote:
>>
>>> My preference is that we set it to NULL. This will aid in debugging as any
>>> dereferences to NULL will immediately trap. Leaving the value unchanged
>>> could result in further manipulation of an invalid memory location and
>>> program corruption.
>>
>> If we do this, do we then want to
>>
>> (a) not have a new symbol version; or
>>
>> (b) have a new symbol version with the old version being an alias of the 
>> new (so that new binaries that may rely on it being set to NULL don't run 
>> with old glibc - similar to the symbol versioning of <fenv.h> functions 
>> whose return type changed from void to int in C99 TC1, for example); or
>>
>> (c) have a new symbol version with the old version not changing *ptr on 
>> error?
> 
> IMO we should be conservative and do (c), and document in NEWS, Release wiki
> page, and hopefully the manual.
> 
> There are arguments for (b) given that the manual page says the behaviour
> is undefined,

I don't consider the argument strong though. I imagine it 
is what Andries made up (lacking further information) on the
day he wrote the page. 

> but I do not believe this will result in the best user
> experience.
> 
> Other opinions?

Setting the pointer to NULL + (c) sounds good to me.

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/