On 7/5/20 9:29 AM, Christophe JAILLET wrote:
> Le 14/02/2017 à 17:43, yla...@apache.org a écrit :
>> Author: ylavic
>> Date: Tue Feb 14 16:43:25 2017
>> New Revision: 1782986
>>
>> URL:http://svn.apache.org/viewvc?rev=1782986&view=rev
>> Log:
>> util_filter: better ap_pass_brigade() vs empty brigades.
>>
>> Modified:
>> httpd/httpd/trunk/server/util_filter.c
>>
>> Modified: httpd/httpd/trunk/server/util_filter.c
>> URL:http://svn.apache.org/viewvc/httpd/httpd/trunk/server/util_filter.c?rev=1782986&r1=1782985&r2=1782986&view=diff
>> ==============================================================================
>> --- httpd/httpd/trunk/server/util_filter.c (original)
>> +++ httpd/httpd/trunk/server/util_filter.c Tue Feb 14 16:43:25 2017
>> @@ -584,9 +584,9 @@ AP_DECLARE(apr_status_t) ap_pass_brigade
>> apr_bucket_brigade *bb)
>> {
>> if (next) {
>> - apr_bucket *e;
>> + apr_bucket *e = APR_BRIGADE_LAST(bb);
>> - if ((e = APR_BRIGADE_LAST(bb)) && APR_BUCKET_IS_EOS(e) &&
>> next->r) {
>> + if (e != APR_BRIGADE_SENTINEL(bb) && APR_BUCKET_IS_EOS(e) &&
>> next->r) {
>> /* This is only safe because HTTP_HEADER filter is always in
>> * the filter stack. This ensures that there is ALWAYS a
>> * request-based filter that we can attach this to. If the
>
> Hi,
>
> I don't really understand the change above.
>
> The commit description is clear. 'ap_pass_brigade' should deal better with
> empty brigades.
>
> However, if the last bucket is an EOS bucket, how could it be a sentinel?
> My understanding is that this change is a no-op, but I may have missed
> something.
>
> What is the rational for it?
If the brigade is empty then APR_BRIGADE_LAST(bb) points to the sentinel. Hence
The first condition of the if is not met and we
jump over the block. If the brigade is not empty we check if the last bucket
which is now not the sentinel is the eos bucket.
In the previous code the first condition in the if was always true, and I am
not sure what happened with the second condition in
case e was the sentinel.
Regards
Rüdiger
