aprantl marked an inline comment as done.
aprantl added inline comments.
================
Comment at: lldb/source/Expression/DWARFExpression.cpp:2077
+ // with the expression result, so the debugger can print missing
+ // members as "<optimized out>" or something.
::memset(curr_piece.GetBuffer().GetBytes(), 0, piece_byte_size);
----------------
labath wrote:
> vsk wrote:
> > FTR I'm not really sure this case is allowed by the dwarf standard. Under
> > DW_OP_piece the standard references a "preceding simple location
> > description" -- istm like an error if the stack is empty. My $0.0002 :)
> I think this is fine -- an "empty location description" (section 2.6.1.1.4 of
> DWARF4) is a kind of a "simple location description" (sect. 2.6.1.1).
>
> The part that worries me more is this: "Each simple location description that
> is a DWARF expression is evaluated independently of any others (as though on
> its own separate stack, if any).". I think that means we should reset/clear
> the stack after each DW_OP_piece, but we don't currently do that (we just pop
> the topmost value). However, I am not sure if this has any impact on valid
> DWARF expressions (though it can cause us to produce bogus values for invalid
> ones).
That's cute, so with our current implementation one could write a communicating
DWARF expression like:
DW_OP_lit1 DW_OP_dup DW_OP_piece 1 DW_OP_piece 1
Is the second byte supposed to be 1 or undef?
;-)
I agree, we should probably clear the stack.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D72880/new/
https://reviews.llvm.org/D72880
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