comp: Fix bitfields to allow underaligned fields after them to take padding space. #1950
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
|
emilio
force-pushed
the
bitfield-edge-cases
branch
from
f1f1bca to
a4558a2
Compare
…adding space. Fixes #1947. There are two separate issues here: First, the change in comp.rs ensures that we don't round up the amount of storage to the alignment of the bitfield. That generates the "expected" output in #1947 (`__BindgenBitfieldUnit<[u8; 3], u16>`). But that's still not enough to fix that test-case because __BindgenBitfieldUnit would be aligned and have padding, and Rust won't put the extra field in the padding. In order to ensure the bitfield starts at the right alignment, but that Rust can put stuff in the extra field, we need to make a breaking change and split the generated fields in two: One preceding that guarantees alignment, and the actual storage, bit-aligned. This keeps the existing behavior while fixing that test-case.
emilio
force-pushed
the
bitfield-edge-cases
branch
from
a4558a2 to
88a7849
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #1947.
There are two separate issues here: First, the change in comp.rs ensures
that we don't round up the amount of storage to the alignment of the
bitfield. That generates the "expected" output in #1947
(
__BindgenBitfieldUnit<[u8; 3], u16>).But that's still not enough to fix that test-case because
__BindgenBitfieldUnit would be aligned and have padding, and Rust won't
put the extra field in the padding.
In order to ensure the bitfield starts at the right alignment, but that
Rust can put stuff in the extra field, we need to make a breaking change
and split the generated fields in two: One preceding that guarantees
alignment, and the actual storage, bit-aligned.
This keeps the existing behavior while fixing that test-case.