Mach-O 64-bit format does not support 32-bit absolute addresses

[cre8eve]

Hey everyone  I am trying to write numbers from one array to another, but I am stuck with the topic error.
I have
section .data
 
source:    db      '5', '6', '7', '8'
dest:       db   '0', '0', '0', '0'

section .text
...
mov rax, source ; copying the first number (5) into rax register
mov dest, rax    ; ERROR: Mach-O 64-bit format does not support 32-bit absolute addresses
...

I compile it with -f macho64 option

How can I rewrite from one array to another? Any suggestions?
Thanks in advance.

[Frank Kotler]

Well... Finally... at the end of the day... I think (not sure of this) there's an error in Nasm's "-f macho64" output format. You may need to use (G)as, or perhaps try Yasm.

However, we can discuss what else is wrong with your code, and why it wouldn't have worked anyway.

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section .data
 
source:    db      '5', '6', '7', '8'
dest:       db   '0', '0', '0', '0'

What you've got here is characters, not numbers. They're numbers, too, of course, but probably not the numbers you want.

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section .text
...
mov rax, source ; copying the first number (5) into rax register

Comment does not match code. You've moved the address of your array into rax.

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mov rax, [source]

This would move the first 64-bit number (8 bytes) into rax. rax would be 0x3030303038373635. I doubt this is what you want. To move a single byte into a register, try:

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mov al, [source]

This is still going to be the character '5', not the number 5.

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mov dest, rax    ; ERROR: Mach-O 64-bit format does not support 32-bit absolute addresses
...

This attempts to move rax into the address of "dest" - an immediate value. Reminds me of the old Hendrix tune "If Six Were Nine". Simply isn't going to work - no such instruction.

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mov [dest], rax

... would move rax - 64-bits, 8 bytes - into your buffer... which is only 4 bytes, causing an overflow. Probably what you want - to move just one byte (one character):

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mov [dest], al

I don't know what to advise you, Cre8eve. You appear to be fairly new at this (no offense intended - none of us are born knowing this stuff) and as such, probably don't want to mess with a potentially buggy format. AFAIK, "-f macho32" (or just "-f macho") works. There may be a problem convincing a 64-bit ld that you want 32-bit code - there is in Linux. For Linux, we tell ld "-m elf_i386", but that isn't going to work for MacOS. "objdump -i" produces a list of supported formats - this may work for Mac, too(?). Then... if you attempt to link against C libraries, there may be an issue of incompatible libraries (there is in Linux)...

I wish I had a better answer for ya!

Best,
Frank

[Keith Kanios]

Put DEFAULT REL near the top of your source if you are using macho64: more info

I also reposted an older Mac OS X demo, which may help guide you: http://forum.nasm.us/index.php?topic=1972.0