Re: [9fans] Non-stack-based calling conventions

["Eris Discordia" <eris.discordia@gmail.com>]

On Sun, 17 Feb 2008 00:04:31 -0000, Brantley Coile <brantley@coraid.com>
wrote:

> The relocation formats for the 6600 assembler wasn't that complicated,
> much less than coff.  For the Cyber 17/18 the instructions could
> be pc relative and didn't have to be relocated when linked together,
> at least not for the call/return scenario.

I remember the necessity of relocation was not limited to where you had to
link binaries. On the 80286 + MS-DOS combination, lack of virtual memory
hardware (the "real" mode) made relocation inevitable as processes were
not isolated and memory was not multiplexed by the hardware and/or OS.
Without a flat and isolated address space for each process, every
executable had to adjust to where it was being loaded. Hence, the EXE
header and relocation table.

COFF has had to cope with a certain monster dubbed portability; to adapt
to the peculiarities of the many flavors of UNIX (and at least one
Microsoft OS, with MS-COFF). So good it has been practically put out of
business by ELF or... do Plan 9 compilers output COFF object files?

> The 6600 had a field address that was added to the program counter
> to relocate the program.  It also had a field length register to
> make sure you didn't spill off the end.

No far jumps/calls? Was the memory model not segmented?

> All was much simpler than today.

I am actually very grateful for having a flat 32/64 bit address space all
to myself. Even though the curse of managing virtual memory and driving
the associated hardware has been placed on every OS developer, occasional
programmers like me really enjoy the outcome.

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