Cut akbasic_Runtime's static footprint from 10.75 MiB to 2.40 MiB #33

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tachikoma wants to merge 3 commits from feature/reduce_memory_usage into main

pull from: feature/reduce_memory_usage

merge into: andrew:main

andrew:main

andrew:galaga-tutorial

andrew:40

andrew:34

andrew:fix/megademo-80col

andrew:libakstdlib-26

andrew:23

andrew:todo-to-issues

Conversation 1 Commits 3 Files Changed 28 +264 -106

3 Commits

Author	SHA1	Message	Date
Logikoma	eb93bb7da0	Fix 80-column fixtures and tutorial expectations	2026-08-04 16:36:27 -04:00
Tachikoma	1e514f679b	Rework the megademo to fit the 80-column source line limit ... AKBASIC_MAX_LINE_LENGTH's cut from 256 to 80 left seventeen lines of examples/megademo unloadable: the sixteen IM$() picture strings (up to 252 characters) and TUNEA/TUNEB's four-bar PLAY strings (174 and 175). The real ceiling is 78 characters, not 80 -- stdio_readline() refuses a read that fills the 80-byte buffer without a newline, so content plus its terminator must fit in 79. The picture: vaporwave.py's PAYLOAD drops from 240 to 64, so every emitted IM$(NN) = "..." line fits under the ceiling. chop() no longer slices blind; it walks the stream a record at a time -- two characters for a run, three for an R row record -- and never cuts inside one, because the decoder reads a record's tail with MID on the string it is walking and a record straddling two IM$ entries decodes as garbage. The old blind slice at 240 only happened to be safe. verify() now simulates the CHOPPED strings with the cursor threaded across the boundaries exactly the way DRAWSTREAM executes them, so a bad cut is an assertion failure instead of a corrupted screen, and emit_block() asserts every emitted line fits. The picture is 56 strings where it was 16; the decoder needed no changes at all, since it already carries X#/Y# from one IM$ entry to the next. The music: TUNEA and TUNEB each become four PLAY statements, one bar apiece. play.c keeps voice, envelope, level and duration state on the runtime across statements and every PLAY appends to the same queue, so four bars queue exactly as one long string did. Each bar restates the V1T3U9S prefix so a bar dropped by QFULL cannot leave the next batch playing on the drum kit's envelope. Everything still clears the shrunken pools with room to spare: 1625 source lines of 2048, ~704 array slots of 2048, identifiers within the 24-character symtab key. Verified end to end against this branch's build: the demo loads, the offscreen host renders every scene, and the scene-5 still is pixel-identical to vaporwave.py's own preview. The test suite fails the same seventeen cases with and without this commit. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01ACffnV6F7sxQuG3Y8a1L3s	2026-08-04 11:13:31 -04:00
Tachikoma	17af2d406c	Cut akbasic_Runtime's static footprint from 10.75 MiB to 2.40 MiB ... Nothing in this interpreter mallocs; every pool is a fixed array sized by an AKBASIC_MAX_* constant, so sizeof(akbasic_Runtime) is a compile-time number and most of it was headroom nobody was using. Measured concurrent-use high-water marks off examples/breakout and examples/megademo -- the two most demanding programs this interpreter runs -- against each pool's ceiling: AKBASIC_MAX_ENVIRONMENTS 32 -> 12 (measured peak concurrency: 6-7) AKBASIC_MAX_FUNCTIONS 64 -> 8 (measured: 0, neither program uses DEF FN) AKBASIC_MAX_ARRAY_VALUES 4096 -> 2048 (measured peak: 1618 slots) AKBASIC_MAX_SOURCE_LINES 9999 -> 2048 (measured: ~1270-1496 non-blank lines) AKBASIC_SYMTAB_MAX_SLOTS 256 -> 172 (no caller ever requests more than 128) AKBASIC_SYMTAB_MAX_KEY 64 -> 24 (longest identifier measured: 11 chars) AKBASIC_MAX_LINE_LENGTH 256 -> 80 (Commodore BASIC's own line limit) AKBASIC_MAX_VARIABLES (128) is untouched on purpose: breakout alone reaches 121 of 128 concurrent named variables, so it has the least slack of any pool measured and is not a shrink candidate. akbasic_Variable.name shrinks from AKBASIC_MAX_STRING_LENGTH (256) to AKBASIC_SYMTAB_MAX_KEY: every variable name is registered with akbasic_symtab_set() right after this field is populated (akbasic_environment_create(), src/environment.c), and that call already refuses anything AKBASIC_SYMTAB_MAX_KEY characters or longer. The wider field was headroom nothing could ever put a byte into. Two defects surfaced while testing the line-length drop against the golden corpus, both fixed here because the 80-byte ceiling makes them routine rather than theoretical: - sourcepath (runtime.h) was borrowing AKBASIC_MAX_LINE_LENGTH by accident. It holds a directory, not a line of BASIC, and this checkout's own test paths are 81+ characters deep -- every golden test failed to load until this split into its own AKBASIC_MAX_SOURCE_PATH_LENGTH, backed by PATH_MAX the way libakerror already sizes its own path buffers. - src/sink_stdio.c's stdio_readline() called aksl_fgets() but never checked its own documented contract: a full buffer with no trailing newline means the line was longer than the buffer, and the unread remainder is still in the stream. Unchecked, the next readline() picks that remainder up as its own statement -- a real line silently becomes two wrong ones instead of a clean AKBASIC_ERR_BOUNDS refusal. At 256 bytes this was theoretical; at 80 it is not, so it now refuses loudly. tests/value_pool.c's test_pool_is_untouched_by_scopes() was pinned to the old 4x1024=4096 pool math (four max-size arrays proving nothing leaked); rewritten to 2x1024=2048 for the same proof against the new AKBASIC_MAX_ARRAY_VALUES. Known consequence, tracked in andrew/akbasic#32 rather than worked around here: two files in the protected tests/reference/ corpus (language/functions/mod.bas, language/flowcontrol/nestedforloopwaitingfor command.bas) have 82-character lines and cannot be shortened -- MAINTENANCE.md and CMakeLists.txt:585 are explicit that tests/reference/ is never edited to suit this interpreter. Twelve tests/language/ cases and one docs/18 line are in the same position but are this project's own content. Shipping 80 anyway, with the fallout tracked rather than hidden, was an explicit call on this PR rather than something decided here. Verified: cmake --build build-akgl && ctest --test-dir build-akgl, 97/112 (15 known failures, all AKBASIC_MAX_LINE_LENGTH-related, filed as #32). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>	2026-08-03 21:44:16 -04:00