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When attempting to compile the following Objective-C++ code with
CodeView debug info:
void (^b)(void) = []() {};
The generated debug metadata contains a structure like the following:
!43 = !DICompositeType(tag: DW_TAG_structure_type, name: "__block_literal_1", scope: !6, file: !6, line: 1, size: 168, elements: !44)
!44 = !{!45, !46, !47, !48, !49, !52}
...
!52 = !DIDerivedType(tag: DW_TAG_member, scope: !6, file: !6, line: 1, baseType: !53, size: 8, offset: 160, flags: DIFlagPublic)
!53 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !54)
!54 = !DICompositeType(tag: DW_TAG_class_type, file: !6, line: 1, flags: DIFlagFwdDecl)
Note that the member node (!52) is unnamed, but rather than pointing to
a DICompositeType directly, it points to a DIDerivedType with tag
DW_TAG_const_type, which then points to the DICompositeType. However,
the CodeView assembly printer currently assumes that the base type for
an unnamed member will always be a DICompositeType, and attempts to
perform that cast, which triggers an assertion failure, since in this
case the base type is actually a DIDerivedType, not a DICompositeType
(and we would have to get the base type of the DIDerivedType to reach
the DICompositeType). I think the debug metadata being generated by the
frontend is correct (or at least plausible), and the CodeView printer
needs to handle this case.
This patch teaches the CodeView printer to unwrap any qualifier types.
The qualifiers are just dropped for now. Ideally, they would be applied
to the added indirect members instead, but this occurs infrequently
enough that adding the logic to handle the qualifiers correctly isn't
worth it for now. A FIXME is added to note this.
Additionally, Reid pointed out that the underlying assumption that an
unnamed member must be a composite type is itself incorrect and may not
hold for all frontends. Therefore, after all qualifiers have been
stripped, check if the resulting type is in fact a DICompositeType and
just return if it isn't, rather than assuming the type and crashing if
that assumption is violated.
Differential Revision: https://reviews.llvm.org/D43803
llvm-svn: 326255
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