================
@@ -16983,6 +16983,26 @@ void Sema::DiscardMisalignedMemberAddress(const Type
*T, Expr *E) {
}
}
+/// If packing reduces \p FD below the alignment required by its type, return
+/// the alignment it is reduced to. __attribute__((packed)) reduces every
+/// field; #pragma pack(N) only reduces fields that require more than N.
+static std::optional<CharUnits> getPackedFieldAlignment(const ASTContext &Ctx,
+ const FieldDecl *FD) {
+ const RecordDecl *RD = FD->getParent();
+ bool IsPacked = FD->hasAttr<PackedAttr>() || RD->hasAttr<PackedAttr>();
+ const auto *MFAA = RD->getAttr<MaxFieldAlignmentAttr>();
+ if (!IsPacked && !MFAA)
+ return std::nullopt;
+
+ CharUnits TypeAlignment = Ctx.getTypeAlignInChars(FD->getType());
+ if (!IsPacked &&
+ Ctx.toCharUnitsFromBits(MFAA->getAlignment()) >= TypeAlignment)
+ return std::nullopt;
----------------
aaronpuchert wrote:
That's an interesting development. I forgot that `__attribute__((aligned))` on
`typedef` can also lower alignment. I'd be fine if you skip that for now (since
your focus is packing pragmas), but perhaps we should actually include this
attribute. (Perhaps a bit weird to warn about this under
`-Waddress-of-packed-member`, but the effect is the same. Your motivating
example doesn't care which attribute lowered alignment.)
https://github.com/llvm/llvm-project/pull/219096
_______________________________________________
cfe-commits mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
