mruby-bin-mirb: drop the readline and linenoise completion adapters - #7249

527018c replaced readline, libedit and linenoise in mirb with the built-in multi-line editor and took their detection out of mrbgem.rake. That rake file was also what defined MRB_READLINE_HEADER next to MRB_USE_READLINE, so a config that still defines MRB_USE_READLINE on its own, as the IntelEdison cross target does (build_config/IntelEdison.rb:25), now reaches an #include with nothing to include:

$ MRUBY_CONFIG=IntelEdison rake -j16
...
CPP   mrbgems/mruby-bin-mirb/tools/mirb/mirb_completion.c -> build/host/mrbgems/mruby-bin-mirb/tools/mirb/mirb_completion.pi
mrbgems/mruby-bin-mirb/tools/mirb/mirb_completion.c:45:10: error: #include expects "FILENAME" or <FILENAME>
   45 | #include MRB_READLINE_HEADER
      |          ^~~~~~~~~~~~~~~~~~~
rake aborted!

What is left in the source

Three guarded blocks survived 527018c, none of them reachable:

mirb.c only calls mirb_setup_editor_completion and mirb_get_completions; neither setup function has a caller. The first commit removes the three blocks together with the current_index field that only the readline generator used, so defining MRB_USE_READLINE or MRB_USE_LINENOISE is a no-op, which is what 527018c's message already says ("readline integration has been completely removed").

The second commit brings mrbgems/mruby-bin-mirb/README.md up to date: it still said completion needs "a readline library", listed the three backends, and documented a MRUBY_MIRB_READLINE environment variable that nothing reads. The Tab Completion section now describes the built-in editor.

The third commit removes the define from IntelEdison.rb:25 itself. It selected mirb's readline backend when the config was written; with the last guarded block gone, cc.defines = %w(MRB_USE_READLINE) only replaces the toolchain's default define list with a stale name. With the config loaded, MRuby.targets['core2-32-poky-linux'].cc.defines is [] where it was ["MRB_USE_READLINE"].

Verified

Three builds of the same config (default.gembox, enable_debug, enable_test) into separate build directories: master, this branch, and this branch with conf.cc.defines << 'MRB_USE_READLINE' added. The third one fails on master at the line above and builds here; mirb_completion.o.flags confirms -DMRB_USE_READLINE reached the compiler.

size on the results, master versus branch and branch with the define:

The 11 bytes are the ctx->current_index = 0 store in mirb_completion_free (this config is -O0); the guarded blocks were never compiled without the define, so nothing else moves. Master and the branch with the define are not comparable, since master does not build.

Tab completion was driven through a pty on all three binaries with the same key sequence per case (constant Stri, method String.ne, listing String.n, keyword whi, global $std, local my_var), and the three terminal transcripts are byte-identical (md5sum b80fb4d6…). Excerpts:

1> String          # Stri<Tab>
1> String.new      # String.ne<Tab>
1> String.n
new  name  nil?    # String.n<Tab>
1> while           # whi<Tab>
1> $std
$stdin  $stderr  $stdout
1> my_var          # my_<Tab> after my_var = 1

rake -m test on the branch build: KO 0, Crash 0.

Environment

# master, branch
gcc -std=gnu99 -g -O3 -Wall -Wundef -Werror-implicit-function-declaration -Wwrite-strings -g3 -O0 -DMRBGEM_MRUBY_BIN_MIRB_VERSION=0.0.0 -DMRB_DEBUG -DHAVE_MRUBY_REGEXP_GEM -DMRB_USE_SET -DHAVE_MRUBY_IO_GEM -DMRB_USE_RATIONAL -DMRB_USE_COMPLEX -DMRB_USE_BIGINT -DMRB_USE_DEBUG_HOOK -MMD -c mrbgems/mruby-bin-mirb/tools/mirb/mirb_completion.c
# branch + MRB_USE_READLINE
gcc -std=gnu99 -g -O3 -Wall -Wundef -Werror-implicit-function-declaration -Wwrite-strings -g3 -O0 -DMRB_USE_READLINE -DMRBGEM_MRUBY_BIN_MIRB_VERSION=0.0.0 -DMRB_DEBUG -DHAVE_MRUBY_REGEXP_GEM -DMRB_USE_SET -DHAVE_MRUBY_IO_GEM -DMRB_USE_RATIONAL -DMRB_USE_COMPLEX -DMRB_USE_BIGINT -DMRB_USE_DEBUG_HOOK -MMD -c mrbgems/mruby-bin-mirb/tools/mirb/mirb_completion.c