diff options
Diffstat (limited to 'docs/BOOTSTRAP-OWNERSHIP.md')
| -rw-r--r-- | docs/BOOTSTRAP-OWNERSHIP.md | 38 |
1 files changed, 33 insertions, 5 deletions
diff --git a/docs/BOOTSTRAP-OWNERSHIP.md b/docs/BOOTSTRAP-OWNERSHIP.md index 509db2f..6cc61ce 100644 --- a/docs/BOOTSTRAP-OWNERSHIP.md +++ b/docs/BOOTSTRAP-OWNERSHIP.md @@ -1,7 +1,9 @@ -# the bootstrap does not compile: owned values cannot be moved between locals +# the bootstrap did not compile: owned values could not be moved between locals -status: open, blocks `make` -affects: `make genome`, the `fixpoint` check, the `genome.h is up to date` check +status: resolved. the analyzer gained the two rules proposed below and a clearer +recast diagnostic, and `make genome` reaches its fixpoint from a clean checkout. +see "resolution" at the end; the rest of this note is the record of the problem. +affects: `make genome` and the `fixpoint` check see also: `docs/BORROW.md` ## summary @@ -10,7 +12,7 @@ see also: `docs/BORROW.md` `src/core/core.zc` and `src/compiler/compiler.zc` into a stage-0 image, stage-0 becoming `build/zy0`, and `zy0` compiling the same three files again into the genome. the second compilation runs with lifetime checking enabled and rejects -the compiler's own source. `bin/mkgenome` then reads the diagnostics as if they +the compiler's own source. `mkgenome` then read the diagnostics as if they were an image: ``` @@ -152,4 +154,30 @@ reports. bash src/tools/bootstrap-check.sh ``` -a passing run prints `image ok: <n> bytes`.
\ No newline at end of file +a passing run prints `image ok: <n> bytes`. + +## resolution + +the analyzer (`src/compiler/compiler.zc`) now accepts the three spellings: + +1. **moves into a released owner.** `rt.free(r); r = joined;` moves `joined` into `r` + when `r` was released first and `joined` is an owner of the same block or a deeper + one. `joined` is retired by the move. a destination that still owns something is + still rejected (`still owns an object; overwriting it would leak it`), and so is a + copy of an owner into a fresh declaration. +2. **bounded lends to globals.** `g = m*x;` with `x` an owned local lends `x` to `g`: + `x` keeps ownership and stays usable, and the lend ends when the same block assigns + `g` again. giving `x` away, returning, breaking or leaving the block while the lend + is open is an error (`is lent to global g; assign the global again before ...`). the + lend list is per function and per block depth (`lend_add`, `lend_clear`, + `lend_exit`), so a restore inside a nested branch does not end a lend made outside it. +3. **recasts of plain locals.** `rt.code_blocks = m*block;` failed because `block` came + from `chk_resize`, which returns collector-managed storage, so `block` never owned + anything. the compiler now writes `rt.code_blocks = block;`, and a recast of a plain + local reports `block: isn't an owned object, so there is no ownership to recast` + instead of the old message. + +`methdef` uses the lend for its scratch buffer and the move for the joined token list. +the regressions are `tests/programs/ownmove.zc` and `tests/errors/lend_*.zc`, +`recast_plain.zc` and `move_live_owner.zc`. + |