[LLVMdev] LLVM ERROR: expected relocatable expression

[Eli Friedman]

On Sun, Sep 22, 2013 at 9:43 PM, Shankar Easwaran
<shankare at codeaurora.org>wrote:

>  Hi Eli,
>
> Slightly changed the example :-
>
> .section somedata
> .Ltmpa:
> .word 100
> .Ltmpb:
> .word 60
> .Ltmpc:
> .word 40
> .Ltmpd:
> .word   (.Ltmpa-.Ltmpb)-.Ltmpc
>
> The GNU assembler properly handles the above.
>
> $as -c x.s -o x.o
> $readelf -x 4 x.o
>
> Hex dump of section 'somedata':
>  NOTE: This section has relocations against it, but these have NOT been
> applied to this dump.
>   0x00000000 64003c00 28000000                   d.<.(...
>                                                      ^^^^ (Calculated
> properly too!)
> With clang/llvm-mc
>
> $ llvm-mc -filetype=obj x.s -o x.o
>
> LLVM ERROR: expected relocatable expression
>
> Looks like llvm-mc is more restrictive ?
>
>
>
Emitting the relocation in question requires *negating* the address of a
variable.  I could be wrong, but I'm pretty sure there isn't any way to
represent that in ELF.

-Eli
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