l80 is a linker for CP/M and MS-DOS COM executables.
It reads in object files and libraries created by
a80
and produces executable CP/M-80 binaries from them.
There are not (yet) any assemblers or compilers that
produce 8086 object code for l80. But when such programs
appear, l80 will already be able to handle them.
You can read an in-depth explanation of how the linker and object file format work here.
l80 should build with any
D
compiler for any supported platform. I use
GDC
on
OpenBSD
and that works well.
There is a port of l80 to C that can be compiled for
CP/M, MS-DOS, and Unix. The C port has the following
differences:
- Only the first 15 characters of symbol names are unique.
- On CP/M, the binary is named
ldto avoid conflict with Microsoft L80.
You can build this C version for CP/M with:
$ make cpm
For MS-DOS with:
$ make dos
And for Unix with:
$ make c
usage: l80 binary file1.obj [file2.obj ...]
All object files must end in .obj or .lib.
The .com extension will automatically be appended to
binary.
l80 uses the most simple object format I could devise.
Object files are comprised of control codes and data. There are three control codes:
00: The following byte is literal data.01: The following bytes are a symbol declaration.02: The following bytes are a symbol reference.
l80 uses two passes to generate the final execuatable
binary. The first pass writes all object files and libraries
into a single buffer and then collects all the symbol
declarations and calculates the address of each symbol. The
second pass writes out the executable, replacing references
with the addresses calculated during the first pass.
Libraries are simply collections of object files. They can be created with the ar80 utility.
l80 does not recognize nor remove the code of unused
symbols. Doing so is planned.
The order of the object files and libraries can be very important.
Compilers should implement name mangling for symbols not destined to be globals to prevent spurious duplicate symbol errors.
Probably lots. Test and let me know.
ISC License. See LICENSE for details.
This l80 is in no way related to the linker of the same
name produced by Microsoft, also targeting CP/M-80.
That one uses a very different file format.