Fix pg_file_write() error handling.

Detect fclose() failures; given "ln -s /dev/full $PGDATA/devfull",
"pg_file_write('devfull', 'x', true)" now fails as it should.  Don't
leak a stream when fwrite() fails.  Remove a born-ineffective test that
aimed to skip zero-length writes.  Back-patch to 9.2 (all supported
versions).

diff --git a/contrib/adminpack/adminpack.c b/contrib/adminpack/adminpack.c
index 431a67518742f950691f6286ae6bb617ed10da9a..9fc73978fb7e6957954008a8d8d644528471b6a1 100644 (file)
--- a/contrib/adminpack/adminpack.c
+++ b/contrib/adminpack/adminpack.c
@@ -141,10 +141,10 @@ pg_file_write(PG_FUNCTION_ARGS)
                                        (ERRCODE_DUPLICATE_FILE,
                                         errmsg("file \"%s\" exists", filename)));
 
-               f = fopen(filename, "wb");
+               f = AllocateFile(filename, "wb");
        }
        else
-               f = fopen(filename, "ab");
+               f = AllocateFile(filename, "ab");
 
        if (!f)
                ereport(ERROR,
@@ -152,16 +152,11 @@ pg_file_write(PG_FUNCTION_ARGS)
                                 errmsg("could not open file \"%s\" for writing: %m",
                                                filename)));
 
-       if (VARSIZE(data) != 0)
-       {
-               count = fwrite(VARDATA(data), 1, VARSIZE(data) - VARHDRSZ, f);
-
-               if (count != VARSIZE(data) - VARHDRSZ)
-                       ereport(ERROR,
-                                       (errcode_for_file_access(),
-                                        errmsg("could not write file \"%s\": %m", filename)));
-       }
-       fclose(f);
+       count = fwrite(VARDATA(data), 1, VARSIZE(data) - VARHDRSZ, f);
+       if (count != VARSIZE(data) - VARHDRSZ || FreeFile(f))
+               ereport(ERROR,
+                               (errcode_for_file_access(),
+                                errmsg("could not write file \"%s\": %m", filename)));
 
        PG_RETURN_INT64(count);
 }