Fix "ignoring return value" complaints from commit 96d1f42

jconway · jconway · commit b615b2365690 · 2020-07-04T13:47:21.000-04:00
The cfbot and some BF animals are complaining about the previous read_binary_file commit because of ignoring return value of ‘fread’. So let's make everyone happy by testing the return value even though not strictly needed. Reported by Justin Pryzby, and suggested patch by Tom Lane. Backpatched to v11 same as the previous commit. Reported-By: Justin Pryzby Reviewed-By: Tom Lane Discussion: https://postgr.es/m/flat/969b8d82-5bb2-5fa8-4eb1-f0e685c5d736%40joeconway.com Backpatch-through: 11
diff --git a/src/backend/utils/adt/genfile.c b/src/backend/utils/adt/genfile.c
@@ -167,8 +167,7 @@ read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read,
 			{
 				char	rbuf[1]; 
 
-				fread(rbuf, 1, 1, file);
-				if (!feof(file))
+				if (fread(rbuf, 1, 1, file) != 0 || !feof(file))
 					ereport(ERROR,
 							(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 							 errmsg("file length too large")));

Original file line number	Diff line number	Diff line change
`@@ -167,8 +167,7 @@ read_binary_file(const char *filename, int64 seek_offset, int64 bytes_to_read,`
`167`	`167`	`{`
`168`	`168`	`char rbuf[1];`
`169`	`169`
`170`		`- fread(rbuf, 1, 1, file);`
`171`		`- if (!feof(file))`
	`170`	`+ if (fread(rbuf, 1, 1, file) != 0 \|\| !feof(file))`
`172`	`171`	`ereport(ERROR,`
`173`	`172`	`(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),`
`174`	`173`	`errmsg("file length too large")));`