Hi David,
> .text
> .equ link,0
> .word link
> .equ link, .
> .word link
>
> test.S:7: Error: redefined symbol cannot be used on reloc
The error message is occurring because of a limitation of the assembler.
For any given symbol it only maintains one value. Redefining the
symbol (and then using it) is OK provided that the new value is
absolute, but if it is something that the assembler cannot compute at
assemble-time you get this error message.
> It works just fine on my old msp430-gcc. aka:
> Is there something I am doing wrong or did someone break the assembler?
Break - no, change yes. The problem is that the linker now performs
some code optimizations (referred to as "relaxations") such as converting:
jnz $+6
br label
into:
jz label
provided that "label" is within range of the JZ instruction.
But this means that the *size* of the .text section can change, and so
any value that is PC-relative has to be computed by the linker, not the
assembler.
What happened with the old msp430-gcc assembler was that it was able to
convert:
.text
.equ link, 0
.word link
.equ link, .
.word link
into:
.text
.word 0
.word .text + 2
ie it replaced references to "link" with references to an absolute value
and a section relative value. But the new assembler cannot do this as
".text + 2" might no longer be the correct value for that location.
So - what can you do ?
Well, if you do not need these headers to be in the .text section then
you can just move them to the .data section:
.data
.equ link, 0
.word link
.equ link, .
.word link
This assembles just fine. (The assembler knows that the linker will not
change the size of the .data section so it is free to replace symbol
references with section relative references).
Or you could use multiple symbols, rather than just redefining the same
symbol. For example:
.macro foo start=0
.if start == 1
.equ link\@, 0
.else
.equ link\@, .
.endif
.word link\@
.endm
.text
.globl main
main:
foo 1
foo
foo 0
This creates lots of symbols called linkNNNN when NNNN is the invocation
count of the foo macro.
I hope that this helps.
Cheers
Nick
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