67c588c481
C doesn't allow empty structs but Clang/GCC support them and give them a size of 0.
LLDB implements this by checking the tag kind and if it's `DW_TAG_structure_type` then
we give it a size of 0 via an empty external RecordLayout. This is done because our
internal TypeSystem is always in C++ mode (which means we would give them a size
of 1).
The current check for when we have this special case is currently too lax as types with
`DW_TAG_structure_type` can also occur in C++ with types defined using the `struct`
keyword. This means that in a C++ program with `struct Empty{};`, LLDB would return
`0` for `sizeof(Empty)` even though the correct size is 1.
This patch removes this special case and replaces it with a generic approach that just
assigns empty structs the byte_size as specified in DWARF. The GCC/Clang special
case is handles as they both emit an explicit `DW_AT_byte_size` of 0. And if another
compiler decides to use a different byte size for this case then this should also be
handled by the same code as long as that information is provided via `DW_AT_byte_size`.
Reviewed By: werat, shafik
Differential Revision: https://reviews.llvm.org/D105471
38 lines
880 B
C++
38 lines
880 B
C++
struct Empty {};
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class EmptyClass {};
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struct SingleMember {
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int i;
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};
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class SingleMemberClass {
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int i;
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};
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struct PaddingMember {
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int i;
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char c;
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};
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class PaddingMemberClass {
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int i;
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char c;
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};
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const unsigned sizeof_empty = sizeof(Empty);
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const unsigned sizeof_empty_class = sizeof(EmptyClass);
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const unsigned sizeof_single = sizeof(SingleMember);
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const unsigned sizeof_single_class = sizeof(SingleMemberClass);
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const unsigned sizeof_padding = sizeof(PaddingMember);
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const unsigned sizeof_padding_class = sizeof(PaddingMemberClass);
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int main() {
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Empty empty;
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EmptyClass empty_class;
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SingleMember single;
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SingleMemberClass single_class;
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PaddingMember padding;
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PaddingMemberClass padding_class;
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// Make sure globals are used.
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return sizeof_empty + sizeof_empty_class + sizeof_single +
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sizeof_single_class + sizeof_padding + sizeof_padding_class;
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}
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