[libiberty] does anyone use regex.c with REGEX_MALLOC?

[Jeff Law]

On 07/29/2016 05:30 AM, Aldy Hernandez wrote:
> On 07/25/2016 06:30 PM, Manuel López-Ibáñez wrote:
>> On 25/07/16 21:16, Joseph Myers wrote:
>>> On Mon, 25 Jul 2016, Jeff Law wrote:
>>>
>>>> I'll pre-approve removing those bits.  Alternately, you could look to
>>>> resync
>>>> with glibc, though that could prove painful after 15 years of
>>>> divergence.
>>>
>>> The current glibc implementation is completely different; the libiberty
>>> version was replaced in glibc many years ago.  Obsolete libiberty by
>>> gnulib for all its users and you get a portable version of the current
>>> glibc regex that way....
>>
>> BTW, this is what Ayush is trying to do:
>>
>> https://gcc.gnu.org/ml/gcc-patches/2016-07/msg01302.html
>>
>> https://gcc.gnu.org/wiki/replacelibibertywithgnulib
>>
>> It would be great if someone could review his patches. I cannot approve
>> them myself.
>>
>> You could even ask him to look next at replacing the libiberty version
>> of regex.c with gnulib's in GCC. It is on his TODO list.
>
> Well, if libiberty is going to be replaced en masse by gnulib, then
> there's no sense in me cleaning up libiberty's regex.
>
> Out of curiosity I tested gnulib's regex implementation by building
> glibc (since it seems to be the same code) with my -Walloca patch
> (-Walloca-larger-than=4096).  Cursory tests show that libc's regex*.c
> are in much better shape with regards to unbounded allocas.  Actually, I
> only see one real problem and one possible false positive.
>
> For the curious, the possible unbounded alloca is in gnulib's regcomp.c:
>
>       if ((bufp->syntax & RE_ICASE) && dfa->mb_cur_max > 1)
>         {
>           unsigned char *buf = alloca (dfa->mb_cur_max), *p;
>
> Before I spend any more time on this, is there a plan to review Ayush's
> work for say GCC 7?  I obviously only care about regex* right now, or
> any alloca users in libiberty :).
I'm not sure who's taking the lead on reviewing Ayush's work.  But I do 
expect someone will own it at some point in advance of stage1 close.

jeff