9 a.out output module

This chapter describes the a.out output module which can be selected with the ‘-Faout’ option.

9.1 Legal

This module is written in 2008-2016,2020,2021 by Frank Wille and is covered by the vasm copyright without modifications.

9.2 Additional options for this module

‘-mid=<machine id>’

Sets the MID field of the a.out header to the specified value. The MID defaults to 2 (Sun020 big-endian) for M68k and to 100 (PC386 little-endian) for x86.

9.3 General

This output module emits the a.out (assembler output) format, which is an older 32-bit format for Unix-like operating systems, originally invented by AT&T.

9.4 Restrictions

The a.out output format, as implemented in vasm, currently supports the following architectures:

• - M68k
• - i386

The following standard relocations are supported by default:

• - absolute, 8, 16, 32 bits
• - pc-relative, 8, 16, 32 bits
• - base-relative

Standard relocation table entries occupy 8 bytes and don’t include an addend, so they are not suitable for most RISC CPUs. The extended relocations format occupies 12 bytes and also allows more relocation types.

9.5 Known Problems

Some known problems of this module at the moment:

• - The extended relocation format is not supported.

9.6 Error Messages

This module has the following error messages:

• - 3004: section attributes <attr> not supported
• - 3008: output module doesn’t allow multiple sections of the same type
• - 3010: section <%s>: alignment padding (%lu) not a multiple of %lu at 0x%llx