rjmccall added a comment.
I don't mean the actual layout used by Windows targets; I mean the layout used
by the ms_struct pragma / attribute.
================
Comment at: lib/AST/RecordLayoutBuilder.cpp:1606
@@ -1605,1 +1605,3 @@
+ } else if (ExplicitFieldAlign)
+ FieldOffset = llvm::RoundUpToAlignment(FieldOffset, ExplicitFieldAlign);
----------------
It does still seem to be limited by platforms that ignore natural alignment,
though, and by #pragma pack (2) and so on, so at least some of the
modifications made to FieldAlign need to be reflected in ExplicitFieldAlign.
I had to spend some time trying to work out counter-examples, but I did
convince myself that the effect of the fallback here is correct. My concern
was that there was a way we might round up to FieldAlign when we only needed to
round up to ExplicitFieldAlign, which could matter if there were another
properly-aligned position within the current storage unit. However, the second
clause of the first condition will only trigger at the very end of a storage
unit, which means that there cannot be any other properly-aligned positions
within it.
It might be wrong for zero-width bit-fields, though, since we'll always round
up to FieldAlign instead of ExplicitFieldAlign.
================
Comment at: lib/AST/RecordLayoutBuilder.cpp:1614
@@ -1610,3 +1613,3 @@
UnpackedFieldOffset = llvm::RoundUpToAlignment(UnpackedFieldOffset,
UnpackedFieldAlign);
}
----------------
This should follow the same logic that you use for FieldOffset, unless I'm
missing something.
http://reviews.llvm.org/D14980
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