[Clang] Clarify the [[trivial_abi]] documentation.
#143243
Merged
Conversation
This file contains hidden or 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
cor3ntin
added
documentation
clang:frontend
|
@llvm/pr-subscribers-clang Author: Corentin Jabot (cor3ntin) ChangesFixes #36667 Full diff: https://github.com/llvm/llvm-project/pull/143243.diff 1 Files Affected:
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 40b9f8142bb69..19d5a76246bf0 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -4431,7 +4431,11 @@ destroy the object before returning. The lifetime of the copy of the parameter
in the caller ends without a destructor call when the call begins.
If a type is trivial for the purpose of calls, it is assumed to be trivially
-relocatable for the purpose of ``__is_trivially_relocatable``.
+relocatable for the purpose of ``__is_trivially_relocatable`` and
+``__builtin_is_cpp_trivially_relocatable``.
+The copy constructor of a an object of such type might not be called
+when the object is passed to a function. Therefore, the ``trivial_abi``
+attribute should not be applied to objects that contain pointer to themselves.
Attribute ``trivial_abi`` has no effect in the following cases:
|
Sirraide
reviewed
Jun 9, 2025
erichkeane
reviewed
Jun 9, 2025
| ``__builtin_is_cpp_trivially_relocatable``. | ||
| The copy constructor of an object of such type might not be called | ||
| when the object is passed to a function. Therefore, the ``trivial_abi`` | ||
| attribute should not be applied to objects that contain pointers to themselves. |
There was a problem hiding this comment.
I might suggest generalizing this more... it isn't just 'pointer to themselves', it is 'does something meaningful in the copy constructor' or the 'copy constructor has some meaningful side effects'. <dont take either fo those, neither are right, but hopefully a jumping off point).
There was a problem hiding this comment.
What about something like...
When used as a function argument, this attribute instructs the compiler it may omit the call to the copy constructor. Thus, side effects of the copy constructor are potentially not executed. For example, objects that contain pointers to themselves or sub-objects that would be updated during a copy should not be marked as trivial.
I'm not THRILLED with my last sentence, so feel free to come up with somethign better.
cor3ntin
force-pushed
the
corentin/trivial_abi_doc
branch
from
1b8013a to
002d009
Compare
erichkeane
approved these changes
Jun 9, 2025
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/55/builds/12538 Here is the relevant piece of the build log for the reference |
tomtor
pushed a commit
to tomtor/llvm-project
that referenced
this pull request
Jun 14, 2025
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 #36667