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Commit0f47e83

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Fix alignment problem with bbsink_copystream buffer.
bbsink_copystream wants to store a type byte just before the buffer,but basebackup.c wants the buffer to be aligned so that it can callPageIsNew() and PageGetLSN() on it. Therefore, instead of inserting1 extra byte before the buffer, insert MAXIMUM_ALIGNOF extra bytesand only use the last one.On most machines this doesn't cause any problem (except perhaps forperformance) but some buildfarm machines with -fsanitize=alignmentdump core.Discussion:http://postgr.es/m/CA+TgmoYx5=1A2K9JYV-9zdhyokU4KKTyNQ9q7CiXrX=YBBMWVw@mail.gmail.com
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‎src/backend/replication/basebackup_copy.c

Lines changed: 11 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -152,18 +152,22 @@ bbsink_copystream_begin_backup(bbsink *sink)
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{
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bbsink_copystream*mysink= (bbsink_copystream*)sink;
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bbsink_state*state=sink->bbs_state;
155+
char*buf;
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/*
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* Initialize buffer. We ultimately want to send the archive and manifest
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* data by means of CopyData messages where the payload portion of each
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* message begins with a type byte, so we set up a buffer that begins with
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* a the type byte we're going to need, and then arrange things so that
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* the data we're given will be written just after that type byte. That
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* will allow us to ship the data with a single call to pq_putmessage and
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* without needing any extra copying.
160+
* message begins with a type byte. However, basebackup.c expects the
161+
* buffer to be aligned, so we can't just allocate one extra byte for the
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* type byte. Instead, allocate enough extra bytes that the portion of
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* the buffer we reveal to our callers can be aligned, while leaving room
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* to slip the type byte in just beforehand. That will allow us to ship
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* the data with a single call to pq_putmessage and without needing any
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* extra copying.
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*/
165-
mysink->msgbuffer=palloc(mysink->base.bbs_buffer_length+1);
166-
mysink->base.bbs_buffer=mysink->msgbuffer+1;
168+
buf=palloc(mysink->base.bbs_buffer_length+MAXIMUM_ALIGNOF);
169+
mysink->msgbuffer=buf+ (MAXIMUM_ALIGNOF-1);
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mysink->base.bbs_buffer=buf+MAXIMUM_ALIGNOF;
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mysink->msgbuffer[0]='d';/* archive or manifest data */
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/* Tell client the backup start location. */

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