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Postings from October 2003
On Thursday, October 23, 2003, at 10:30 pm, Nicholas Clark wrote:
> On Thu, Oct 23, 2003 at 09:47:21PM +0100, Dave Mitchell wrote:
>> On Wed, Oct 22, 2003 at 10:15:52PM +0200, Elizabeth Mattijsen wrote:
>>> Well, maybe someone can figure out what is going on here and maybe
>>> we'll get a fix for 5.8.2?
>
> I meant to reply to this "not likely unless someone does it real soon"
>
>
>> Whether this will be integrated in 5.8.2 is up to Nick.
>
> I confess I don't understand the sharing system well enough to be a
> good
> judge of this.
>
>> The gory details:
>>
>> While in shared interpeter context, the call to sv_setsv() that
>> updates
>> the (shared interpreter) RV at $a[0] to refer to the new (shared
>> interpreter) [] also causes the old thing the RV was pointing to to be
>> freed. But a cunning bit of code in sv_unref_flags() doesn't free
>> the old
>> referent immediately; instead it is converted into a mortal, and so
>> freed
>> later. This is apparently to handle stuff like $a = $a->[0]. However,
>> this
>> means that the mortal was added to the tmps stack of the *shared
>> interpreter*, which never gets freed. Adding a SAVETMPS/FREETMPS
>> within
>> the shared context block of code solved the problem.
>
> Is it safe to add to maint?
> [I know that it's desirable to stem the leak, but is it unlikely to add
> new bugs?]
>
>> + if (SvTYPE(ssv) == SVt_PVAV) /* #24061 */
>> + AvREAL_on(ssv);
>
> Is AvREAL documented anywhere?
Yes it is.
>
>> CALLER_CONTEXT;
>> }
>>
>> @@ -436,6 +438,12 @@
>> if (target) {
>> SV *tmp;
>> SHARED_CONTEXT;
>> + /* #24255: sv_setsv() (via sv_unref_flags()) may cause a
>> + * deferred free with sv_2mortal(). Ensure that the free_tmps
>> + * is done within this inpterpreter. DAPM.
>> + */
>> + ENTER;
>> + SAVETMPS;
>> tmp = newRV(SHAREDSvPTR(target));
>> sv_setsv_nomg(SHAREDSvPTR(shared), tmp);
>> SvREFCNT_dec(tmp);
>> @@ -444,6 +452,8 @@
>> SvOBJECT_on(SHAREDSvPTR(target));
>> SvSTASH(SHAREDSvPTR(target)) = (HV*)fake_stash;
>> }
>> + FREETMPS;
>> + LEAVE;
>> CALLER_CONTEXT;
>> }
>> else {
>
> This bit seems safe to me. (But who am I to judge?)
>
> Nicholas Clark
>
I think it is safe.
Arthur
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