[LLD] Evaluation of DEFINED linker script directive produces wrong output

[edward-jones]

The following linker script causes unexpected behaviour when APPLE is not defined by any input objects. The unexpected output is that APPLE will resolve to '1' instead of '2'.

APPLE = DEFINED (APPLE) ? 1 : 2;

It appears that when the symbol is first processed it is added to the symbol table with the expected value, however LLD reevaluates symbol assignments, and during these subsequent evaluations of the expression the DEFINED now returns 1 as APPLE has been inserted in the symbol table.

[llvmbot]

@llvm/issue-subscribers-lld-elf

[renesas-kyle-finch]

I have run into a similar issue. I think it has to do with when the symbol being set is the same symbol being checked by DEFINED.

Building off the original example when APPLE is not defined:

Scenario 1:
APPLE = DEFINED (APPLE) ? APPLE : 2;
This evaluates to 0 instead of 2

Scenario 2:
ORANGE = DEFINED (APPLE) ? APPLE : 2;
This correctly evaluates to 2

[MaskRay]

Created #65866