# Add DW_OP_call* alternative to refer to variable value

Section 2.5.1.5, pg 36

With the link time optimization debug info generation where we want to emit
debug info for types/variables etc. early and only afterwards ammend it with
additional information (locations etc.), we ran into a problem similar to
[Issue 160811.1](160811.1.html), but where we need the
value of some local variable (in [PR 77589](http://gcc.gnu.org/PR77589) for
`DW_AT_byte_stride` location expression that is on a type).

`DW_OP_call4`/`call_ref` aren't IMHO usable here, because to use those in the
middle of DWARF expressions it is needed that the referenced DIE's
`DW_AT_location` is actually a valid DWARF expression (and additionally that
it as a result adds exactly one new value on the DWARF stack and ideally
doesn't use any earlier stack slots).

That is not the case in many cases though, the variable could have `DW_OP_reg*`
as its location description, or DWARF expression followed by `DW_OP_stack_value`,
or could not have `DW_AT_location` at all and have instead `DW_AT_const_value`,
etc.  When the producer can see the `DW_AT_location` of the DIE referenced by
`DW_OP_call*` together with the DWARF expression where it wants to use `DW_OP_call*`,
it can either inline the expression there, tweak it for the `DW_OP_stack_value`
removal, transform `DW_OP_reg*` into `DW_OP_breg* 0`, etc.  But if it is different
producer that emits the `DW_OP_call*` and different one that adds `DW_AT_location`
for the referenced var, then this doesn't really work.

I think it would be useful to have a `DW_OP_call*` like operator that would not
evaluate the expression from the referenced DIE, but where the producer would
compute the variable's value and push that value into DWARF stack.  Most
likely it would make sense only for integral variables, but that is most
likely all where it is needed.

---

2026-06-08: Closed. This issue was solved by
[230524.1][230524.1] "Location Descriptions on the DWARF Stack".
The call operations can now return any kind of location,
so a call followed by a deref will work regardless of the location.

[230524.1]: https://dwarfstd.org/issues/230524.1.html