tim@crackle.amd.com (Tim Olson) (10/20/88)
In article <909@goofy.megatest.UUCP> djones@megatest.UUCP (Dave Jones) writes: | Even *Sun* binaries are not the same as Sun binaries, or so I heard | today. A fellow told me that the RISC a.out format for sun-4 is | incompatible with Unix (bsd) a.out format, which is what sun-3 uses. | He was steamed because a linker I had written and put in the public | domain would not work on his new machine. Wanted to know if I had | Sun-4 version. It is very hard to create a truly portable object file format that can work on all machines. The problem is the relocation info. Most of the "standard" object file formats (like the BSD a.out or COFF) only define relocation types that were needed on architectures like VAX or 680x0 (i.e. direct or PC-relative 8, 16, and 32-bit references). However, new architectures require different relocation types. For example, most RISC processors load a full 32-bit constant with a sequence of two instructions, like const lr0, extern_value ; load low 16 bits consth lr0, extern_value ; load hi 16 bits Now we need a relocation type that can take a 32-bit absolute address and stuff the upper half into an instruction. Because of this, most vendors extend a.out or COFF to fit their requirements. A fully portable object file format would require a general-purpose linker "evaluation language" which allows not only +/-, but also <<, >>, &, |, etc. -- Tim Olson Advanced Micro Devices (tim@crackle.amd.com)
henry@utzoo.uucp (Henry Spencer) (10/26/88)
In article <23314@amdcad.AMD.COM> tim@crackle.amd.com (Tim Olson) writes: >Because of this, most vendors extend a.out or COFF to fit their >requirements. A fully portable object file format would require a >general-purpose linker "evaluation language" which allows not only +/-, >but also <<, >>, &, |, etc. In case everyone has forgotten, there was an attempt at an IEEE standard for just such a portable format a few years ago ("MUFOM"). Don't know if anything's happened with it since. It looked okay. -- The dream *IS* alive... | Henry Spencer at U of Toronto Zoology but not at NASA. |uunet!attcan!utzoo!henry henry@zoo.toronto.edu