diff --git a/dlls/msvcirt/tests/msvcirt.c b/dlls/msvcirt/tests/msvcirt.c
index fa373d3bc86..45c3bd42175 100644
--- a/dlls/msvcirt/tests/msvcirt.c
+++ b/dlls/msvcirt/tests/msvcirt.c
@@ -2900,36 +2900,66 @@ static void test_ostream(void) {
     ok(os1.unknown == 0, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == NULL, "expected %p got %p\n", NULL, os1.base_ios.sb);
     ok(os1.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os1.base_ios.state);
+    ok(os1.base_ios.delbuf == 0, "expected 0 got %d\n", os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == NULL, "expected %p got %p\n", NULL, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0, "expected 0 got %x\n", os1.base_ios.flags);
+    ok(os1.base_ios.precision == 6, "expected 6 got %d\n", os1.base_ios.precision);
+    ok(os1.base_ios.fill == ' ', "expected 32 got %d\n", os1.base_ios.fill);
+    ok(os1.base_ios.width == 0, "expected 0 got %d\n", os1.base_ios.width);
+    ok(os1.base_ios.do_lock == -1, "expected -1 got %d\n", os1.base_ios.do_lock);
     call_func1(p_ostream_vbase_dtor, &os1);
+    memset(&os1, 0xab, sizeof(ostream));
     pos = call_func3(p_ostream_sb_ctor, &os1, &fb1.base, TRUE);
     ok(pos == &os1, "wrong return, expected %p got %p\n", &os1, pos);
     ok(os1.unknown == 0, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == &fb1.base, "expected %p got %p\n", &fb1.base, os1.base_ios.sb);
     ok(os1.base_ios.state == IOSTATE_goodbit, "expected %d got %d\n", IOSTATE_goodbit, os1.base_ios.state);
+    ok(os1.base_ios.delbuf == 0, "expected 0 got %d\n", os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == NULL, "expected %p got %p\n", NULL, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0, "expected 0 got %x\n", os1.base_ios.flags);
+    ok(os1.base_ios.precision == 6, "expected 6 got %d\n", os1.base_ios.precision);
+    ok(os1.base_ios.fill == ' ', "expected 32 got %d\n", os1.base_ios.fill);
+    ok(os1.base_ios.width == 0, "expected 0 got %d\n", os1.base_ios.width);
+    ok(os1.base_ios.do_lock == -1, "expected -1 got %d\n", os1.base_ios.do_lock);
     ok(fb1.base.allocated == 0xabababab, "expected %d got %d\n", 0xabababab, fb1.base.allocated);
-    call_func1(p_filebuf_ctor, &fb1);
-    pfb = call_func4(p_filebuf_open, &fb1, filename1, OPENMODE_out, filebuf_openprot);
-    ok(pfb == &fb1, "wrong return, expected %p got %p\n", &fb1, pfb);
-    ok(fb1.base.allocated == 1, "expected %d got %d\n", 1, fb1.base.allocated);
     call_func1(p_ostream_vbase_dtor, &os1);
     ok(os1.base_ios.sb == NULL, "expected %p got %p\n", NULL, os1.base_ios.sb);
     ok(os1.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os1.base_ios.state);
     memset(&os1.base_ios, 0xab, sizeof(ios));
     os1.unknown = 0xabababab;
+    os1.base_ios.state = 0xabababab | IOSTATE_badbit;
     pos = call_func2(p_ostream_ctor, &os1, FALSE);
     ok(pos == &os1, "wrong return, expected %p got %p\n", &os1, pos);
     ok(os1.unknown == 0, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == os2.base_ios.sb, "expected %p got %p\n", os2.base_ios.sb, os1.base_ios.sb);
-    ok(os1.base_ios.state == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.state);
+    ok(os1.base_ios.state == (0xabababab|IOSTATE_badbit), "expected %d got %d\n",
+        0xabababab|IOSTATE_badbit, os1.base_ios.state);
+    ok(os1.base_ios.delbuf == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == os2.base_ios.tie, "expected %p got %p\n", os2.base_ios.tie, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0xabababab, "expected %x got %x\n", 0xabababab, os1.base_ios.flags);
+    ok(os1.base_ios.precision == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.precision);
+    ok(os1.base_ios.fill == (char) 0xab, "expected -85 got %d\n", os1.base_ios.fill);
+    ok(os1.base_ios.width == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.width);
+    ok(os1.base_ios.do_lock == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.do_lock);
     call_func1(p_ostream_dtor, &os1.base_ios);
     os1.unknown = 0xabababab;
-    os1.base_ios.state = 0xabababab | IOSTATE_badbit;
     os1.base_ios.delbuf = 0;
+    call_func1(p_filebuf_ctor, &fb1);
+    pfb = call_func4(p_filebuf_open, &fb1, filename1, OPENMODE_out, filebuf_openprot);
+    ok(pfb == &fb1, "wrong return, expected %p got %p\n", &fb1, pfb);
+    ok(fb1.base.allocated == 1, "expected %d got %d\n", 1, fb1.base.allocated);
     pos = call_func3(p_ostream_sb_ctor, &os1, &fb1.base, FALSE);
     ok(pos == &os1, "wrong return, expected %p got %p\n", &os1, pos);
     ok(os1.unknown == 0, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == &fb1.base, "expected %p got %p\n", &fb1.base, os1.base_ios.sb);
     ok(os1.base_ios.state == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.state);
+    ok(os1.base_ios.delbuf == 0, "expected 0 got %d\n", os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == os2.base_ios.tie, "expected %p got %p\n", os2.base_ios.tie, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0xabababab, "expected %x got %x\n", 0xabababab, os1.base_ios.flags);
+    ok(os1.base_ios.precision == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.precision);
+    ok(os1.base_ios.fill == (char) 0xab, "expected -85 got %d\n", os1.base_ios.fill);
+    ok(os1.base_ios.width == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.width);
+    ok(os1.base_ios.do_lock == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.do_lock);
     call_func1(p_ostream_dtor, &os1.base_ios);
     memset(&os1, 0xab, sizeof(ostream));
     pos = call_func3(p_ostream_sb_ctor, &os1, NULL, TRUE);
@@ -2937,11 +2967,32 @@ static void test_ostream(void) {
     ok(os1.unknown == 0, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == NULL, "expected %p got %p\n", NULL, os1.base_ios.sb);
     ok(os1.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os1.base_ios.state);
+    ok(os1.base_ios.delbuf == 0, "expected 0 got %d\n", os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == NULL, "expected %p got %p\n", NULL, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0, "expected 0 got %x\n", os1.base_ios.flags);
+    ok(os1.base_ios.precision == 6, "expected 6 got %d\n", os1.base_ios.precision);
+    ok(os1.base_ios.fill == ' ', "expected 32 got %d\n", os1.base_ios.fill);
+    ok(os1.base_ios.width == 0, "expected 0 got %d\n", os1.base_ios.width);
+    ok(os1.base_ios.do_lock == -1, "expected -1 got %d\n", os1.base_ios.do_lock);
     call_func1(p_ostream_vbase_dtor, &os1);
-    os1.unknown = 0xcdcdcdcd;
     memset(&os1.base_ios, 0xcd, sizeof(ios));
-    memset(&os2, 0xab, sizeof(ostream));
-    os2.vbtable = os1.vbtable;
+    os1.unknown = 0xcdcdcdcd;
+    pos = call_func3(p_ostream_copy_ctor, &os2, &os1, TRUE);
+    ok(pos == &os2, "wrong return, expected %p got %p\n", &os2, pos);
+    ok(os2.unknown == 0, "expected 0 got %d\n", os2.unknown);
+    ok(os2.base_ios.sb == os1.base_ios.sb, "expected %p got %p\n", os1.base_ios.sb, os2.base_ios.sb);
+    ok(os2.base_ios.state == IOSTATE_goodbit, "expected %d got %d\n", IOSTATE_goodbit, os2.base_ios.state);
+    ok(os2.base_ios.delbuf == 0, "expected 0 got %d\n", os2.base_ios.delbuf);
+    ok(os2.base_ios.tie == NULL, "expected %p got %p\n", NULL, os2.base_ios.tie);
+    ok(os2.base_ios.flags == 0, "expected 0 got %x\n", os2.base_ios.flags);
+    ok(os2.base_ios.precision == 6, "expected 6 got %d\n", os2.base_ios.precision);
+    ok(os2.base_ios.fill == ' ', "expected 32 got %d\n", os2.base_ios.fill);
+    ok(os2.base_ios.width == 0, "expected 0 got %d\n", os2.base_ios.width);
+    ok(os2.base_ios.do_lock == -1, "expected -1 got %d\n", os2.base_ios.do_lock);
+    call_func1(p_ostream_vbase_dtor, &os2);
+    memset(&os2.base_ios, 0xab, sizeof(ios));
+    os2.unknown = 0xabababab;
+    os2.base_ios.state = 0xabababab | IOSTATE_badbit;
     os2.base_ios.delbuf = 0;
     os2.base_ios.tie = &os2;
     pos = call_func3(p_ostream_copy_ctor, &os2, &os1, FALSE);
@@ -2955,18 +3006,21 @@ static void test_ostream(void) {
     ok(os2.base_ios.precision == 0xabababab, "expected %d got %d\n", 0xabababab, os2.base_ios.precision);
     ok(os2.base_ios.fill == (char) 0xab, "expected -85 got %d\n", os2.base_ios.fill);
     ok(os2.base_ios.width == 0xabababab, "expected %d got %d\n", 0xabababab, os2.base_ios.width);
+    ok(os2.base_ios.do_lock == 0xabababab, "expected %d got %d\n", 0xabababab, os2.base_ios.do_lock);
     call_func1(p_ostream_dtor, &os2.base_ios);
+    os1.base_ios.sb = NULL;
     pos = call_func3(p_ostream_copy_ctor, &os2, &os1, TRUE);
     ok(pos == &os2, "wrong return, expected %p got %p\n", &os2, pos);
     ok(os2.unknown == 0, "expected 0 got %d\n", os2.unknown);
-    ok(os2.base_ios.sb == os1.base_ios.sb, "expected %p got %p\n", os1.base_ios.sb, os2.base_ios.sb);
-    ok(os2.base_ios.state == IOSTATE_goodbit, "expected %d got %d\n", IOSTATE_goodbit, os2.base_ios.state);
+    ok(os2.base_ios.sb == NULL, "expected %p got %p\n", NULL, os2.base_ios.sb);
+    ok(os2.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os2.base_ios.state);
     ok(os2.base_ios.delbuf == 0, "expected 0 got %d\n", os2.base_ios.delbuf);
     ok(os2.base_ios.tie == NULL, "expected %p got %p\n", NULL, os2.base_ios.tie);
     ok(os2.base_ios.flags == 0, "expected 0 got %x\n", os2.base_ios.flags);
     ok(os2.base_ios.precision == 6, "expected 6 got %d\n", os2.base_ios.precision);
     ok(os2.base_ios.fill == ' ', "expected 32 got %d\n", os2.base_ios.fill);
     ok(os2.base_ios.width == 0, "expected 0 got %d\n", os2.base_ios.width);
+    ok(os2.base_ios.do_lock == -1, "expected -1 got %d\n", os2.base_ios.do_lock);
 
     /* assignment */
     pos = call_func2(p_ostream_ctor, &os1, TRUE);
@@ -2979,6 +3033,7 @@ static void test_ostream(void) {
     os1.base_ios.flags = 0xabababab;
     os1.base_ios.precision = 0xabababab;
     os1.base_ios.width = 0xabababab;
+    os1.base_ios.do_lock = 0xabababab;
     pos = call_func2(p_ostream_assign_sb, &os1, &fb1.base);
     ok(pos == &os1, "wrong return, expected %p got %p\n", &os1, pos);
     ok(os1.unknown == 0xabababab, "expected 0 got %d\n", os1.unknown);
@@ -2990,20 +3045,41 @@ static void test_ostream(void) {
     ok(os1.base_ios.flags == 0, "expected 0 got %x\n", os1.base_ios.flags);
     ok(os1.base_ios.precision == 6, "expected 6 got %d\n", os1.base_ios.precision);
     ok(os1.base_ios.width == 0, "expected 0 got %d\n", os1.base_ios.width);
+    ok(os1.base_ios.do_lock == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.do_lock);
     os1.base_ios.state = 0x8000;
     pos = call_func2(p_ostream_assign_sb, &os1, NULL);
     ok(pos == &os1, "wrong return, expected %p got %p\n", &os1, pos);
+    ok(os1.unknown == 0xabababab, "expected 0 got %d\n", os1.unknown);
     ok(os1.base_ios.sb == NULL, "expected %p got %p\n", NULL, os1.base_ios.sb);
     ok(os1.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os1.base_ios.state);
+    ok(os1.base_ios.special[0] == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.fill);
+    ok(os1.base_ios.delbuf == 0, "expected 0 got %d\n", os1.base_ios.delbuf);
+    ok(os1.base_ios.tie == NULL, "expected %p got %p\n", NULL, os1.base_ios.tie);
+    ok(os1.base_ios.flags == 0, "expected 0 got %x\n", os1.base_ios.flags);
+    ok(os1.base_ios.precision == 6, "expected 6 got %d\n", os1.base_ios.precision);
+    ok(os1.base_ios.width == 0, "expected 0 got %d\n", os1.base_ios.width);
+    ok(os1.base_ios.do_lock == 0xabababab, "expected %d got %d\n", 0xabababab, os1.base_ios.do_lock);
     os2.unknown = 0xcdcdcdcd;
     os2.base_ios.state = 0xcdcdcdcd;
     os2.base_ios.special[0] = 0xcdcdcdcd;
+    os2.base_ios.delbuf = 0xcdcdcdcd;
+    os2.base_ios.tie = (ostream*) 0xcdcdcdcd;
+    os2.base_ios.flags = 0xcdcdcdcd;
+    os2.base_ios.precision = 0xcdcdcdcd;
+    os2.base_ios.width = 0xcdcdcdcd;
+    os2.base_ios.do_lock = 0xcdcdcdcd;
     pos = call_func2(p_ostream_assign, &os2, &os1);
     ok(pos == &os2, "wrong return, expected %p got %p\n", &os2, pos);
     ok(os2.unknown == 0xcdcdcdcd, "expected 0 got %d\n", os2.unknown);
     ok(os2.base_ios.sb == NULL, "expected %p got %p\n", NULL, os2.base_ios.sb);
     ok(os2.base_ios.state == IOSTATE_badbit, "expected %d got %d\n", IOSTATE_badbit, os2.base_ios.state);
     ok(os2.base_ios.special[0] == 0xcdcdcdcd, "expected %d got %d\n", 0xcdcdcdcd, os2.base_ios.fill);
+    ok(os2.base_ios.delbuf == 0, "expected 0 got %d\n", os2.base_ios.delbuf);
+    ok(os2.base_ios.tie == NULL, "expected %p got %p\n", NULL, os2.base_ios.tie);
+    ok(os2.base_ios.flags == 0, "expected 0 got %x\n", os2.base_ios.flags);
+    ok(os2.base_ios.precision == 6, "expected 6 got %d\n", os2.base_ios.precision);
+    ok(os2.base_ios.width == 0, "expected 0 got %d\n", os2.base_ios.width);
+    ok(os2.base_ios.do_lock == 0xcdcdcdcd, "expected %d got %d\n", 0xcdcdcdcd, os2.base_ios.do_lock);
 
     /* flush */
 if (0) /* crashes on native */