Address Copilot review: the prior comment promised that a negative depth would never re-enable splitting, but an arithmetically-balanced later { could bring depth back to 0 and resume flushing mid-stream. Track an explicit 'poisoned' flag set once depth < 0 that permanently disables further flushes for the rest of the input. Adds a regression test where a leading } and a later { would have re-enabled splitting without the poison flag.
The mutable-list-of-bool trick for rebinding-safe flag mutation works but reads poorly. Replace with a _ComponentGroup dataclass carrying lines + unsafe + no_split fields. cpp_main_section now reads as a straight iteration over typed groups; no apologetic comments needed.
- Fix the ComponentMarker docstring's incomplete 'either placement-news or mutates a global' claim — acknowledge that function-local patterns also exist and note the bare-local detection covers them.
- Document that _emits_bare_local's RawExpression detection is intentionally safety-biased: false negatives break compilation, false positives just keep a slightly larger IIFE. Note the CallExpression(..., RawExpression) negative case explicitly.
- Explain the mutable-list-flag pattern in cpp_main_section — dataclass would read cleaner but the pattern is localized.
- Add regression test for a group with BOTH IIFEUnsafeStatement and a bare-local: unsafe wins (flat emission) because a return inside any IIFE, even a single big one, only exits the lambda.
Tests were hardcoding 120 statements and expecting 3 sub-chunks from a 50-cap. Extract the cap as a named module constant and compute the test-input size from it, so bumping the cap doesn't silently invalidate the tests.
Exercise the actual CallExpression(..., RawExpression) pattern that components use for passing raw arguments. The previous test used RawStatement filler which didn't exercise the detection path we wanted to assert doesn't trigger.
A component's group is wrapped in a single IIFE with no sub-splitting when its to_code emits any of: scope-brace RawStatement, direct RawExpression via cg.add (raw bare-local or field-assignment like 'tz.field = x'), or typed AssignmentExpression (cg.variable). Detection is content-aware so entity_helpers' inline-comment RawStatements and RawExpression-as-CallExpression-arg don't false-positive. Adds 4 regression tests covering each detection path and the non-triggering inverse cases.
safe_mode emits `if (should_enter_safe_mode(...)) return` via
cg.add(RawExpression(...)) to short-circuit the rest of setup() and
boot into safe mode. With setup() split into per-component IIFEs,
that `return` was only exiting the lambda, so the rest of setup() ran
anyway — breaking safe-mode recovery.
Add IIFEUnsafeStatement, a Statement wrapper that marks its containing
component's block for flat emission (no IIFE). safe_mode wraps its
return expression in it. cpp_main_section detects any such statement
in a group and emits that group flat so control-flow constructs like
`return` still affect setup() itself.
IIFEUnsafeStatement.__str__ routes its inner through statement() so
bare Expression subclasses pick up the terminating semicolon. Reported
by @swoboda1337.
The labels were there to help humans scanning the generated main.cpp
find component boundaries, but they were:
- Unreliable: CORE.flush_tasks can interleave coroutines on each
await, so a component's later statements can land in another
component's begin/end block.
- Load-bearing for a pile of complexity: a tuple return from
_wrap_in_iifes, a has_iife flag, a comment-only detector to
suppress trailing end-markers for comment-only components, and
a brittle `"[]()" in line` check that could false-positive on
YAML dumps containing lambda syntax.
- Not actually needed — generated main.cpp is a build artifact
rarely read by anyone, and cg.LineComment("name:") already puts
the component name at the start of its block.
ComponentMarker stays as a pure chunking sentinel — it tells
cpp_main_section where component boundaries are (for grouping) but
produces no C++ output. _wrap_in_iifes returns a plain list again.
Added a regression test for the now-defused case of a comment
containing "[]()" that was previously flagged by review.
- Count { and } characters per line instead of matching whole-line
tokens. Current codegen only emits scope braces as standalone lines
(from cg.with_local_variable()), but the defensive change is robust
against future codegen emitting inline control flow like
`if (cond) {` or `} else {` on one line.
- Add a regression test covering those inline-brace patterns.
- Fix stale docstrings on ComponentMarker and cpp_main_section that
still claimed "stack frame released on return" and described the
IIFEs as "noinline". The IIFEs have no noinline attribute and rely
on scope-based lifetime shortening rather than guaranteed frames.
Rename the bracket markers from "// === X ===" (same on both sides)
to "// === begin X ===" and "// === end X ===" so the generated
main.cpp reads unambiguously when scanning by component. Comment-only
components still get a single "begin X" marker since they have no
IIFE to close.
The marker comment was being emitted as the first line *inside* each
IIFE:
[]() {
// === logger ===
// logger:
// ...
...
}();
That works but buries the component label inside the lambda body, so
scanning generated main.cpp to find "where does component X's setup
live" is harder than it needs to be. Emit the marker before and after
the IIFE instead:
// === logger ===
[]() {
// logger:
// ...
...
}();
// === logger ===
Comment-only components (e.g. sha256, async_tcp, empty platforms like
binary_sensor:) don't grow a useless trailing duplicate marker —
when there's no IIFE to bracket, the marker is emitted once.
Some components (sha256, async_tcp, network, empty text_sensor:, etc.)
emit only a ComponentMarker plus config-dump comments and no actual
C++ statements. Wrapping those in a `[]() { ... }();` IIFE is pure
clutter in the generated main.cpp — the IIFE has no body.
When _wrap_in_iifes sees a chunk whose lines are all // comments,
emit them verbatim instead of wrapping. Peak stack and flash are
unchanged on apollo and neargaragedoor since GCC was already
eliding the empty IIFEs; this just makes the generated code read
cleanly to humans.
Additional measurements showed GCC's -Os inliner re-inlines most IIFE
chunks back into setup() by choice, and the structural scoping alone
captures nearly all of the peak-stack benefit on esp32 without the
flash cost of forcing all chunks to stay as real functions.
Apollo (esp32-s3, -Os) with vs without noinline:
peak setup stack 176 B (noinline) vs 304 B (scope-only)
flash delta +388 B (noinline) vs -504 B (scope-only)
chunks kept 86 vs 20
Issue #15796 is an LVGL-setup class of bug that has only surfaced on
esp32 after years in the field; the extra guarantee that noinline
provides is not worth the flash cost in practice. Also rename the
helper from _wrap_in_noinline_iifes to _wrap_in_iifes to match.
The C++ standard-attribute spelling [[gnu::noinline]] placed between a
lambda's parameter list and body binds to the return type, not the
call operator. GCC 14 silently ignores it and emits -Wattributes
warnings at every chunk site. Switch to GCC's __attribute__((...))
syntax which binds to operator() as intended.
Measured impact on apollo-r-pro-1-eth (esp32-s3, -Os) vs the broken
[[gnu::noinline]] version: setup() frame 160 B -> 32 B, peak stack
304 B -> 176 B (another -42%). Flash grows by 888 B because all 86
chunks now stay as separate functions instead of GCC inlining the
small ones (which it was free to do when the attribute was ignored).
Net vs baseline -Os: peak stack 1264 B -> 176 B (-86%); flash
+388 B (<0.05% of a typical esp32 partition).
Generated setup() is a single monolithic function whose stack frame
scales super-linearly with config size. On a 5,943-line apollo build
the frame reached 1,264 B at -Os; extrapolation onto larger configs
(e.g. the 16k-line LVGL config in #15796) plausibly overflows the
8 KB loop task stack before safe_mode can increment its boot counter.
Emit a ComponentMarker sentinel at the start of each component's
to_code output, then have cpp_main_section wrap each component's
block (and sub-splits of up to 50 statements within each block) in a
noinline IIFE lambda. Each lambda's ENTRY frame is released on
return, bounding peak stack to setup() frame + max chunk frame.
Measured on apollo-r-pro-1-eth (esp32-s3, -Os):
setup() frame 1264 B -> 160 B
max chunk frame n/a -> 144 B
peak setup stack 1264 B -> 304 B (-76%)
total flash 792,471 B -> 791,995 B (-476 B)
The brace-depth guard in _wrap_in_noinline_iifes ensures we never
split between the RawStatement("{") / RawStatement("}") pair emitted
by cg.with_local_variable() (currently only wifi), so scoped locals
stay intact.
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>
J. Nick Koston