Avoid runtime failure in CopyXLogRecordToWAL with sanitizers (cf. 46ab07f) (#554)

alexanderlaw · Matthias van de Meent · commit 97361da612f6 · 2025-09-15T15:28:25.000+02:00
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -1325,7 +1325,8 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,
 		}
 
 		Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || rdata_len == 0);
-		memcpy(currpos, rdata_data, rdata_len);
+		if (rdata_len > 0)
+			memcpy(currpos, rdata_data, rdata_len);
 		currpos += rdata_len;
 		CurrPos += rdata_len;
 		freespace -= rdata_len;

Original file line number	Diff line number	Diff line change
`@@ -1325,7 +1325,8 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,`
`1325`	`1325`	`}`
`1326`	`1326`
`1327`	`1327`	`Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD \|\| rdata_len == 0);`
`1328`		`- memcpy(currpos, rdata_data, rdata_len);`
	`1328`	`+ if (rdata_len > 0)`
	`1329`	`+ memcpy(currpos, rdata_data, rdata_len);`
`1329`	`1330`	`currpos += rdata_len;`
`1330`	`1331`	`CurrPos += rdata_len;`
`1331`	`1332`	`freespace -= rdata_len;`