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.
J. Nick Koston