Brummel
3e087d759a
Five §"..." cross-refs survived the main sweep because they live
inside jsonc Schema-comments — clause-5 fence-skip would treat any
[label](path) there as literal text, not as a navigable link.
Instead of touching the schema-comment style (it is self-documenting
where it sits, against the field it qualifies), this commit adds
prose paragraphs just outside the fence that turn the same
cross-references into real links:
- Before the Def jsonc block: pointer to memory-model.md
(canonical-form rule for cross-module class/type names) and
embedding-abi.md (exported fn surface).
- Before the Type jsonc block: pointer to memory-model.md for
Type::Con.name scoping and Type::Fn parameter-mode metadata.
Also re-phrases an intra-file §"Str ABI" self-reference in
str-abi.md to "the Str ABI table below" — file-only granularity
makes a self-link sense-less; the reader wants intra-file
direction, which prose carries fine without a link.
Tests: design_index_pin (5/5) + docs_honesty_pin (5/5) stay green.
86 lines
4.2 KiB
Markdown
86 lines
4.2 KiB
Markdown
# Str ABI
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## Heap-Str primitives
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The runtime ships a small family of operations that produce or
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transform heap-allocated `Str` values uniformly across static-Str
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and heap-Str inputs (the consumer ABI is identical between
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realisations — see the Str ABI table below). All take their
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input(s) by `borrow` and return an owned `Str`. Each is registered as a builtin in
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`crates/ailang-check/src/builtins.rs`, lowered inline in
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`crates/ailang-codegen/src/lib.rs::lower_app` to a `call ptr @ailang_<name>`,
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and backed by a `runtime/str.c` C helper.
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- `int_to_str : (borrow Int) -> Str` — decimal rendering
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of an `Int`. Backs `Show Int` in the
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[prelude](prelude-classes.md).
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- `bool_to_str : (borrow Bool) -> Str` — `"true"`/`"false"`.
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Backs `Show Bool` in the [prelude](prelude-classes.md).
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- `float_to_str : (borrow Float) -> Str` —
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type-installed; codegen is reserved and not yet shipped.
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- `str_clone : (borrow Str) -> Str` — allocates a fresh
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heap-Str copy of the input's bytes. Backs `Show Str` in the
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[prelude](prelude-classes.md).
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- `str_concat : (borrow Str, borrow Str) -> Str` — combines two `Str`
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values into a single owned `Str`.
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General-purpose; commonly used in Show bodies for labelled output
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(`(app str_concat "label=" (app int_to_str x))`).
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The four Show-backers above are not directly observable to the
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LLM-author writing a `Show <T>` instance — the prelude's instance
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bodies dispatch into them. `str_concat` IS directly observable
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because the LLM-author calls it explicitly when authoring an
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instance body that wants to combine fragments.
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Primitive output for `Str` values goes through `io/print_str`
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directly; values of other primitive types route through the
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polymorphic `print` helper (see [prelude classes](prelude-classes.md)),
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which feeds the heap-Str result of `show x` into `io/print_str`.
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`==`, `<`, `<=`, `>`, `>=` REMAIN primitive operators. Class methods
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are accessed by name (`eq x y`, `lt x y`, …), not via these
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operators.
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Arithmetic operators (`+`, `-`, `*`, `/`) stay primitive and
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per-type.
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**Str ABI.** A `Str` is a pointer to a structure with `i64 len` at
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offset 0 followed by `len` bytes plus a trailing `NUL` at offset 8.
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Two realisations share this consumer ABI:
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| Realisation | Origin | rc_header | Memory |
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|-------------|-------------------------------------------------|-----------|-----------------------------------------|
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| static-Str | string literals (`@.str_*` LLVM globals) | none | `.rodata`, packed-struct `<{ i64, [N+1 x i8] }>` |
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| heap-Str | runtime allocations (`int_to_str`, `float_to_str`, ...) | yes, at `payload - 8` | `malloc`'d via `ailang_rc_alloc(8 + len + 1)` |
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Every consumer (`@puts`, `@strcmp`, `@ail_str_eq`,
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`@ail_str_compare`) GEPs `+8` from the Str pointer to reach the
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bytes, regardless of realisation. The byte-comparison semantics
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are inherited from libc `strcmp` — locale-independent, NUL-
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terminated.
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The heap-Str realisation participates in standard RC (see
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[memory model](memory-model.md)): the
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`rc_header` slot eight bytes before the `len` field is managed
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by `ailang_rc_alloc` / `ailang_rc_inc` / `ailang_rc_dec` exactly
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like any other RC-allocated cell. The static-Str realisation has
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no `rc_header` slot at all; the bytes at `payload - 8` belong to
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the previous global in `.rodata` and reading them is undefined.
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**The static-Str non-RC invariant is enforced at codegen.** Two
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mechanisms keep static-Str pointers out of `ailang_rc_dec` along
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every shipping execution path: (1) the non-escape lowering pass
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and the move-tracking partial-drop logic
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prevent let-binders or pattern-binders for static-Str literals
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from reaching scope-close drop emission; (2) the `Type::Con { name: "Str" }`
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carve-outs in `field_drop_call` and in the `Term::App` arm of
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`drop_symbol_for_binder` (both in `crates/ailang-codegen/src/drop.rs`)
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route the rare case that *does* reach drop emission through
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`ailang_rc_dec`, which itself only fires for heap-Str at runtime
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(static-Str pointers never carry a live rc_header; if codegen ever
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let one through, the runtime would corrupt `.rodata`-adjacent
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memory). No runtime guard backs the invariant up; the codegen
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proof is the protection.
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Ratified by: `crates/ail/tests/e2e.rs`.
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