Fix some memory leaks in the WAL receiver

These are old leaks, that can pile up if a WAL receiver stays alive,
waiting for new WAL data after the sender has switched to a new
timeline.

While this is technically a bug, the impact is minimal and would only
become noticeable if the WAL sender handles a lot of timeline switches,
so no backpatch is done.  Note that in most cases, primary_conninfo
would be updated in a standby to point to a new sender, meaning a
restart of the WAL receiver.  Let's be clean on HEAD, though.

Author: DaeMyung Kang <charsyam@gmail.com>
Discussion: https://postgr.es/m/20260426170100.847923-1-charsyam@gmail.com
Discussion: https://postgr.es/m/20260426170219.849330-1-charsyam@gmail.com

diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 8185412a8103eb044aefea6788c576ba03a10981..df03dae5836423f96fc1c389f93c34fcd69f1167 100644 (file)
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -302,6 +302,9 @@ WalReceiverMain(const void *startup_data, size_t startup_data_len)
        if (sender_host)
                pfree(sender_host);
 
+       /* Initialize buffers for processing messages */
+       initStringInfo(&reply_message);
+
        first_stream = true;
        for (;;)
        {
@@ -325,6 +328,7 @@ WalReceiverMain(const void *startup_data, size_t startup_data_len)
                                         errdetail("The primary's identifier is %s, the standby's identifier is %s.",
                                                           primary_sysid, standby_sysid)));
                }
+               pfree(primary_sysid);
 
                /*
                 * Confirm that the current timeline of the primary is the same or
@@ -405,9 +409,8 @@ WalReceiverMain(const void *startup_data, size_t startup_data_len)
                                walrcv->walRcvState = WALRCV_STREAMING;
                        SpinLockRelease(&walrcv->mutex);
 
-                       /* Initialize LogstreamResult and buffers for processing messages */
+                       /* Initialize LogstreamResult for processing messages */
                        LogstreamResult.Write = LogstreamResult.Flush = GetXLogReplayRecPtr(NULL);
-                       initStringInfo(&reply_message);
 
                        /* Initialize nap wakeup times. */
                        now = GetCurrentTimestamp();