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Running a REPL against a C lib

Situation: you have a C lib (header/s + obj/ar/shared)

Idea: automatically make a program that is a REPL linked against this lib, you enter C code, can interact with everything exposed in the header (declare variables with lib types, call lib functions, ...)

example/

Example/PoC with example/mylib:

$ cd example
$ make -f mylib.makefile && ./mylib
Type `;help` for a list of command
(*^^),u~~ sayhi; ty
Expression is of type: fun(times: int) -> void
(*^^),u~~ sayhi(2);
hi
hi
Result:
_: void
   = ()
(*^^),u~~

If you really don't want to use make (why?):

$ make -Bnf mylib.makefile
cc -O2   -c -o mylib.o mylib.c
cc ../cintre/preparer.c -o preparer.exe -O2
./preparer.exe ../cintre/standard.h -Pno-emit-decl -Pno-emit-incl -o a-standard.h
./preparer.exe mylib.h -o a-mylib.h -O2
./preparer.exe -m ./a-standard.h ./a-mylib.h -o c-mylib.c
cc -c c-mylib.c -o c-mylib.o -O2 -I. -I../cintre
cc -c ../cintre/cintre.c -o cintre.o -O2 -DUSE_READLINE -D_DEFAULT_SOURCE -D_XOPEN_SOURCE=600
cc mylib.o c-mylib.o cintre.o -o mylib -O2  -lc -lm -lreadline

Bluntly the steps are:

  • build mylib.o
  • build pr (one time)
  • pr standard.h make an interface (or "adapter") to stdlib/stdio/string... (one time)
  • pr mylib.h make an adapter with mylib.o
  • pr -m merge and list namespaces in a way cintre.o can use
  • build c-mylib.c
  • build cintre.o, the main() of the REPL (here with readline) (one time)
  • link mylib.o c-mylib.o and cintre.o

The driver.Makefile does exactly that, see example/Makefile.

Bugs

Assumes platform:

  • has 8 bits bytes (ie. CHAR_BIT == 8);
  • is little endian (ie. (char[4]){0xd6, 0xff, 0x00, 0x00} == (int)0xff2d);
  • respects sizeof(size_t) == sizeof(void*) (which is "not guarenteed", but like..).

It also collapses long and long long into the largest (ie. at runtime sizeof(long) == sizeof(long long) and usually == 2*sizeof(int)).

(wip and such)

breaking

  • fix precedence in a = 1 ? 2 : 3
  • pr: bitfields here and there
  • pr: array size/align

progress

  • pr: macros, like Err codes
  • more conversions in _fit_expr_to_slot
  • handle bitfields in runtime types

opti/cleanup

  • maybe reverse the sp and vsp to have sane zero init (// xxx: sizeof stack)
  • limit avoidable capture-copying
  • go through tokn(...) to reduce expansion in favor of locals
  • something in using cstream to lex and rewind makes lskdjlksj go to the stmt decl route as if 2 idents in a row
  • more coverage
  • pr: "ptr tail" in emit_forward => is a hack on fun/arr declarator, so do it proper
  • pr: is getting weird again (eg. emit_forward for ptr to x, emit_adpt_type_val for param[n], size/align situation for arrays, ..)
  • n -> logn ns search
  • (i386, core linux, qemu, tcc.tcz) tcc: error: undefined symbol '_dso_handle'

the GitHub "Need inspiration?" bit was "animated-spoon"