Attempt to port PDP-11 LINKer to PC C/C++ — learning how the linker works, the hard way.

The code (partially) ported from MACRO-11 sources to C/C++. Port source: RT-11 LINK V05.45.

• Nikita Zimin (@nzeemin)
• Vladimir Voroshilov (@voroshil)
• @ilynxy

Currently the PCLINK11 links most of test OBJ files properly, but we have some troubles linking tests with libraries.

The source code is able to compile under Windows (VS2013/VS2015), and also under Linux/MacOS (gcc/clang, use the Makefile).

Command line:

pclink11 <input files and options>

Options (both / and - prefixes are allowed):

• -QUIET — Minimizes verbosity level
• -VERBOSITY:N — Specifies verbosity level; N=1..6; default is 2
• -EXECUTE:filespec — Specifies the name of the memory image file
• -NOBITMAP -X — Do not emit bit map
• -WIDE -W — Produces a load map that is 132-columns wide
• -ALPHABETIZE -A — Lists global symbols on the link map in alphabetical order
• -SYMBOLTABLE -STB — Generates a symbol table file (.STB file)
• -MAP — Generates map file
• -FOREGROUND -R — Foreground link
• -LDA -L — LDA output
• -FORLIB -F — Include FORLIB.OBJ
• -T:address — Specify transfer address
• -M:address — Modify initial stack
• -B:address — Specify bottom address for link
• -H:address — Specify top address for link
• -Q:section=address — Set section to absolute address
• --version — Show the program version information
• --help — Show quick help on the command line options

Input files and options are space-separated.

Examples:

• pclink11 HELLO.OBJ — link the object file, will produce HELLO.SAV executable
• pclink11 -MAP -SYMBOLTABLE -EXECUTE:LD.SYS LD.OBJ SYSLIB.OBJ -X — link object file with system library, produce map file and symbol file, save output as LD.SYS, do not put bitmap in the first block
• pclink11 TEST1.OBJ TEST2.OBJ -MAP -WIDE -A — link two object files, generate map file with wide format, alphabetize list of symbols

Folder tests contains more than 100 sub-folders with .OBJ files.

First, we use RT-11 simulator written by Dmitry Patronov to produce "etalon" or "original" output files, they renamed with -11 suffix — see !runtest11.cmd command file. Then, we run the pclink11 with to produce "our" output files, they renamed with -my suffix — see !runtestmy.cmd command file and testrunner utility. And finally, we compare "original" files with "our" files, line-to-line or byte-to-byte, using testanalyzer utility.

"Our" MAP files differs in the first line (program name, date/time, no page number), and there's no paging, so no page header lines. SAV/SYS/REL and STB files are binary, compared byte-to-byte, should be no differences. Log files are absolutely different, we're not comparing them, but in "our" log files we're looking for "SUCCESS"/"ERROR" and so on.

First priority:

• Fix bugs for the failing test cases

Second priority:

• Need more tests, currently we have 123 test cases
• Reduce amount of logging, add option for verbosity level
• Process other command-line options, including file-specific ones

Not implemented now, and not sure we will:

• Link for foreground execution with -R or -FOREGROUND option, produce .REL file
• LDA output — produce a file in absolute binary loader format (option -L)
• Overlays
• Linkage with separated instructions/data spaces

• DEC-11-ZLDA-D PDP-11 LINK-11 Linker and LIBR-11 Librarian May71
• AA-PD6PA-TC RT–11 Volume and File Formats Manual
• macro-11 - cross-assembler by Richard Krehbiel