Author: David Blaikie Date: 2022-10-14T19:32:57Z New Revision: 037f856681268c793c660389b4d6407367e68190
URL: https://github.com/llvm/llvm-project/commit/037f856681268c793c660389b4d6407367e68190 DIFF: https://github.com/llvm/llvm-project/commit/037f856681268c793c660389b4d6407367e68190.diff LOG: Itanium ABI: Pack non-pod members of packed types Seems there's a narrow case - where a packed type doesn't pack its base subobjects (only fields), but when packing a field of the derived type, GCC does pack the resulting total object - effectively packing the base subobject. So ensure that this non-pod type (owing to it having a base class) that is packed, gets packed when placed in /another/ type that is also packed. This is a (smallish?) ABI fix to a regression introduced by D117616 - but that regression/ABI break hasn't been released in LLVM as-yet (it's been reverted on the release branch from the last two LLVM releases - I probably should've just reverted the whole patch while we hashed out this and other issues) so this change isn't itself an ABI break, as far as LLVM releases are concerned (for folks releasing their own copies of LLVM from ToT/without the LLVM release branch, and didn't opt into the clang-abi-compat 14 or below (soon to be 15 or below, I guess I should say) then this would be an ABI break against clang from the last 9 months or so) Differential Revision: https://reviews.llvm.org/D135916 Added: Modified: clang/lib/AST/RecordLayoutBuilder.cpp clang/test/SemaCXX/class-layout.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp index dea7450613cc3..a897d4c832300 100644 --- a/clang/lib/AST/RecordLayoutBuilder.cpp +++ b/clang/lib/AST/RecordLayoutBuilder.cpp @@ -1891,6 +1891,7 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, llvm::Triple Target = Context.getTargetInfo().getTriple(); bool FieldPacked = (Packed && (!FieldClass || FieldClass->isPOD() || + FieldClass->hasAttr<PackedAttr>() || Context.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver15 || Target.isPS() || Target.isOSDarwin())) || diff --git a/clang/test/SemaCXX/class-layout.cpp b/clang/test/SemaCXX/class-layout.cpp index df63141fc36dd..f3106ec422dff 100644 --- a/clang/test/SemaCXX/class-layout.cpp +++ b/clang/test/SemaCXX/class-layout.cpp @@ -642,3 +642,17 @@ struct t2 { _Static_assert(_Alignof(t1) == 1, ""); _Static_assert(_Alignof(t2) == 1, ""); } // namespace non_pod_packed + +namespace non_pod_packed_packed { +struct B { + int b; +}; +struct FromB : B { +} __attribute__((packed)); +struct C { + char a[3]; + FromB b; +} __attribute__((packed)); +_Static_assert(__builtin_offsetof(C, b) == 3, ""); +} + _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
