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

alexanderlaw · Matthias van de Meent · commit 5f7b1c853841 · 2025-08-06T18:27:07.000+02:00
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -1336,7 +1336,8 @@ 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
`@@ -1336,7 +1336,8 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,`
`1336`	`1336`	`}`
`1337`	`1337`
`1338`	`1338`	`Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD \|\| rdata_len == 0);`
`1339`		`- memcpy(currpos, rdata_data, rdata_len);`
	`1339`	`+ if (rdata_len > 0)`
	`1340`	`+ memcpy(currpos, rdata_data, rdata_len);`
`1340`	`1341`	`currpos += rdata_len;`
`1341`	`1342`	`CurrPos += rdata_len;`
`1342`	`1343`	`freespace -= rdata_len;`