cmd/gc: pad structs which end in zero-sized fields
For a non-zero-sized struct with a final zero-sized field,
add a byte to the size (before rounding to alignment). This
change ensures that taking the address of the zero-sized field
will not incorrectly leak the following object in memory.
reflect.funcLayout also needs this treatment.
Fixes #9401
Change-Id: I1dc503dc5af4ca22c8f8c048fb7b4541cc957e0f
Reviewed-on: https://go-review.googlesource.com/2452
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/runtime/runtime_test.go b/src/runtime/runtime_test.go
index 1688364..c4de3e2 100644
--- a/src/runtime/runtime_test.go
+++ b/src/runtime/runtime_test.go
@@ -247,3 +247,44 @@
}
}
}
+
+func TestTrailingZero(t *testing.T) {
+ // make sure we add padding for structs with trailing zero-sized fields
+ type T1 struct {
+ n int32
+ z [0]byte
+ }
+ if unsafe.Sizeof(T1{}) != 8 {
+ t.Errorf("sizeof(%#v)==%d, want 8", T1{}, unsafe.Sizeof(T1{}))
+ }
+ type T2 struct {
+ n int64
+ z struct{}
+ }
+ if unsafe.Sizeof(T2{}) != 16 {
+ t.Errorf("sizeof(%#v)==%d, want 16", T2{}, unsafe.Sizeof(T2{}))
+ }
+ type T3 struct {
+ n byte
+ z [4]struct{}
+ }
+ if unsafe.Sizeof(T3{}) != 2 {
+ t.Errorf("sizeof(%#v)==%d, want 2", T3{}, unsafe.Sizeof(T3{}))
+ }
+ // make sure padding can double for both zerosize and alignment
+ type T4 struct {
+ a int32
+ b int16
+ c int8
+ z struct{}
+ }
+ if unsafe.Sizeof(T4{}) != 8 {
+ t.Errorf("sizeof(%#v)==%d, want 8", T4{}, unsafe.Sizeof(T4{}))
+ }
+ // make sure we don't pad a zero-sized thing
+ type T5 struct {
+ }
+ if unsafe.Sizeof(T5{}) != 0 {
+ t.Errorf("sizeof(%#v)==%d, want 0", T5{}, unsafe.Sizeof(T5{}))
+ }
+}
