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.
PlatformIO's idedata may list flash images that do not exist on disk
(e.g. a tasmota tinyuf2.bin referenced by the adafruit_qtpy_esp32s3_n4r2
board). Previously the CLI passed every entry straight to esptool, which
aborted the entire flash with "No such file or directory". The dashboard
path is unaffected because it flashes the pre-merged firmware.factory.bin
produced by the post-build step, which already tolerates missing inputs.
Filter non-existent extra_flash_images with a warning so a stale or
incorrect platform-declared image no longer breaks esphome run.
Fixes https://github.com/esphome/esphome/issues/15634
- TemplatableFn = delete now catches both stateful lambdas AND stateless
lambdas with inconvertible return types (e.g., string -> int)
- Add test for to_exp with non-string output_type (lambda-wraps result)
Specialize TemplatableValue so non-string types use function-pointer-only
storage (4 bytes on 32-bit) instead of the tagged union with std::function
support (8 bytes). The std::string specialization retains full support for
VALUE, STATIC_STRING, FLASH_STRING, and stateful lambdas.
Codegen now wraps non-string constants in stateless lambdas automatically,
so the generated C++ always assigns a function pointer.
J. Nick Koston