Fix a segfault in swarmvtab that could occur if there was an error in the SQL

statement passed to the constructor. Add other test cases.

FossilOrigin-Name: 6ce8b7ca62fcf97875395fc1a989179309e0abb48d4465658ef0d871434ea057

test/swarmvtabfault.test

@@ -0,0 +1,61 @@
+# 2017-07-15
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.  The
+# focus of this file is error handling in the swarmvtab extension.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix swarmvtabfault
+
+ifcapable !vtab {
+  finish_test
+  return
+}
+
+proc fetch_db {file} {
+  forcedelete $file
+  sqlite3 dbX $file
+  dbX eval { CREATE TABLE t1(a INTEGER PRIMARY KEY, b) }
+  dbX close
+}
+
+forcedelete test.db1
+do_execsql_test 1.0 {
+  ATTACH 'test.db1' AS aux;
+  CREATE TABLE aux.t1(a INTEGER PRIMARY KEY, b);
+  INSERT INTO aux.t1 VALUES(1, NULL);
+  INSERT INTO aux.t1 VALUES(2, NULL);
+  INSERT INTO aux.t1 VALUES(9, NULL);
+  DETACH aux;
+} {}
+
+faultsim_save_and_close
+do_faultsim_test 1.1 -faults oom* -prep {
+  faultsim_restore_and_reopen
+  db func fetch_db fetch_db
+  load_static_extension db unionvtab
+  db eval {
+    CREATE VIRTUAL TABLE temp.xyz USING swarmvtab(
+        'VALUES
+        ("test.db1", "t1", 1, 10),
+        ("test.db2", "t1", 11, 20)
+        ', 'fetch_db'
+    );
+  }
+} -body {
+  execsql { SELECT a FROM xyz }
+} -test {
+  faultsim_test_result {0 {1 2 9}} {1 {sql error: out of memory}}
+}
+
+finish_test
+