Use extern "C++" scopes for explicit specializations after P2615R1 Meaningful Exports
#6074
+17
−9
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
StephanTLavavej
changed the title
extern "C++" scopes for explicit specializations after P2615R1extern "C++" scopes for explicit specializations after P2615R1 Meaningful Exports
Member
Author
|
I'm mirroring this to the MSVC-internal repo. Please notify me if any further changes are pushed, otherwise no action is required. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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Outdated suggestions cannot be applied.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.
WG21-P2615R1 Meaningful Exports forbids
extern "C++"from being directly applied to an explicit specialization. Now, every declaration is either a name-declaration or a special-declaration. An explicit-specialization is considered a special-declaration. But when directly applyingextern "C++", the grammar for linkage-specialization requires that theexternstring-literal name-declaration syntax cannot accept a special-declaration.Clang 17 implemented P2615R1 as a DR in C++20 mode, but as of Clang 20 they don't enforce this rule (yet?). @xiangfan-ms brought this to my attention as he was implementing P2615R1 in MSVC.
The fix is simple: use
extern "C++" { ... }scopes.I am allowing the
_Codecvt_guardhelper to permanently remain in this scope, as it's not harmful, and I didn't think it was worth the effort to pull outside of the scope. (Indeed, right now the entire STL is marked withextern "C++"as a workaround.)