pdp11-c0

Ritchie cc pass 1: the parser / front end. Reads preprocessed C, writes the intermediate expression-tree stream that c1 turns into PDP-11 code.

pdp11-c0 source.i tmp1 tmp2 [-P] [-V]

• This is the genuine 2.9BSD c0 (near byte-identical upstream to 2.8's), carrying the LP64 fixes the 2.8 port lacked: cmst[] moved out of tree()'s dead stack frame (the 2.8 port segfaults on the first large function), a filename[] overflow guard for long host paths, and correct subsp/strp carry on SEQNC nodes.
• -P emits profiling counters (cc -p); -V compiles for text overlays (cc -V).
• 16-bit target semantics on a 64-bit host: the target's int stays 2 bytes; only the compiler's own word assumptions were widened.

Documentation

• Design — the first pass -- the lexer, the expression trees, and the intermediate emission.
• User guide — how cc drives it and how to run it standalone.
• docs/porting.md — the porting guide: the anonymous- union tree nodes, pointer-in-int, and the stack-frame story.

Build and test

make          # builds ../../bin/pdp11-c0
make check    # covered by tests/c0/ and the cc end-to-end suite at
              # the repo root, plus the native-compiler oracle
              # (oracle/run.sh) against the 1981 passes