dyung wrote:
> > Hi @Michael137, we are seeing a failure in one of our internal tests that I
> > bisected back to this change. Consider the following code:
> > ```c++
> > struct X
> > {
> > static const int constant = 1;
> > int x;
> >
> > X() { x = constant; }
> > };
> > const int X::constant;
> >
> > int main()
> > {
> > X x;
> > x.x = X::constant;
> > x.x = X::constant;
> > x.x = X::constant;
> > x.x = X::constant;
> > x.x = X::constant;
> > return 0;
> > }
> > ```
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Prior to your change, the compiler would generate the following DWARF for
> > the constant value:
> > ```
> > 0x0000003a: DW_TAG_member
> > DW_AT_name ("constant")
> > DW_AT_type (0x00000057 "const int")
> > DW_AT_decl_file ("/home/dyung/sandbox/test.cpp")
> > DW_AT_decl_line (3)
> > DW_AT_external (true)
> > DW_AT_declaration (true)
> > DW_AT_const_value (1)
> > ```
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > After your change, the DW_AT_const_value is gone from this DW_TAG_member
> > group, but doesn't appear anywhere else in the DWARF output which seems to
> > indicate that it was dropped completely which does not seem to be correct.
> > Is this intended or am I missing something?
>
> Right, we stopped putting the `DW_AT_const_value` on the declaration. Instead
> we put either the location or the constant on the definition, depending on
> what's available. In your example you define the variable out-of-class which
> would generate a `DW_TAG_variable` with a location, so we don't emit the
> constant for it on the definition:
>
> ```
> 0x0000002e: DW_TAG_variable
> DW_AT_specification (0x0000004a "constant")
> DW_AT_location (DW_OP_addr 0x90)
> DW_AT_linkage_name ("_ZN1X8constantE")
> ```
>
> What's the nature of the failure? Would you instead be able to read the value
> out of the definition?
Our test is expecting to find a DW_AT_const_value somewhere in the dwarf output
which it no longer seems to generate. From what I gather from your commit
message, the compiler should now be emitting a new DW_TAG_variable section that
it previously did not with the DW_AT_const_value attached? Or is my
understanding incorrect?
https://github.com/llvm/llvm-project/pull/71780
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