diff options
Diffstat (limited to 'src/test/ui/packed/packed-struct-optimized-enum.rs')
-rw-r--r-- | src/test/ui/packed/packed-struct-optimized-enum.rs | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/src/test/ui/packed/packed-struct-optimized-enum.rs b/src/test/ui/packed/packed-struct-optimized-enum.rs new file mode 100644 index 000000000..5e1a1f518 --- /dev/null +++ b/src/test/ui/packed/packed-struct-optimized-enum.rs @@ -0,0 +1,36 @@ +// run-pass +#[repr(packed)] +struct Packed<T: Copy>(#[allow(unused_tuple_struct_fields)] T); + +impl<T: Copy> Copy for Packed<T> {} +impl<T: Copy> Clone for Packed<T> { + fn clone(&self) -> Self { *self } +} + +fn sanity_check_size<T: Copy>(one: T) { + let two = [one, one]; + let stride = (&two[1] as *const _ as usize) - (&two[0] as *const _ as usize); + let (size, align) = (std::mem::size_of::<T>(), std::mem::align_of::<T>()); + assert_eq!(stride, size); + assert_eq!(size % align, 0); +} + +fn main() { + // This can fail if rustc and LLVM disagree on the size of a type. + // In this case, `Option<Packed<(&(), u32)>>` was erroneously not + // marked as packed despite needing alignment `1` and containing + // its `&()` discriminant, which has alignment larger than `1`. + sanity_check_size((Some(Packed((&(), 0))), true)); + + // In #46769, `Option<(Packed<&()>, bool)>` was found to have + // pointer alignment, without actually being aligned in size. + // e.g., on 64-bit platforms, it had alignment `8` but size `9`. + type PackedRefAndBool<'a> = (Packed<&'a ()>, bool); + sanity_check_size::<Option<PackedRefAndBool>>(Some((Packed(&()), true))); + + // Make sure we don't pay for the enum optimization in size, + // e.g., we shouldn't need extra padding after the packed data. + assert_eq!(std::mem::align_of::<Option<PackedRefAndBool>>(), 1); + assert_eq!(std::mem::size_of::<Option<PackedRefAndBool>>(), + std::mem::size_of::<PackedRefAndBool>()); +} |