[codex] Fix nxplpc Arduino core builds

[zackees]

Summary

Fixes the nxplpc Arduino core build regression by aligning fbuild's LPC8xx build settings with the ArduinoCore-LPC8xx platform.txt recipe and correcting .ino preprocessing behavior.

Root Cause

fbuild's nxplpc config had drifted from the LPC Arduino core recipe: it used GNU++17, release LTO, -nostartfiles, -lc_nano, and extra ARM flags that PlatformIO/ArduinoCore-LPC8xx do not use. The .ino preprocessing path also generated setup()/loop() prototypes before Arduino.h, conflicting with LPC Arduino.h's extern "C" declarations, and stripped explicit user forward declarations from the sketch body.

Changes

• Match nxplpc compile/link flags to ArduinoCore-LPC8xx's GCC recipe.
• Stop auto-generating prototypes for Arduino-owned setup() and loop().
• Preserve existing sketch forward declarations during .ino preprocessing.
• Update LPC fixtures to include Arduino.h and use the correct linkage for the build-flags regression helper.
• Add an ignored clean regression test that builds ~/dev/ArduinoCore-LPC8xx in-process and checks the generated compile command shape.

Validation

• soldr cargo fmt --check
• soldr cargo test -p fbuild-build source_scanner --lib
• soldr cargo test -p fbuild-build nxplpc --lib
• soldr cargo test -p fbuild-build --test nxplpc_build_flags -- --ignored
• soldr cargo test -p fbuild-build --test nxplpc_core_compile_commands -- --ignored

Summary by CodeRabbit

Configuration

• Updated NXP LPC8xx compiler flags (C++ standard, codegen options) and linker configuration for improved compatibility and simplified linking behavior.

Tests

• Added integration test to validate NXP LPC8xx compile command output.
• Enhanced test suite with proper Arduino framework header support across platform fixtures.
• Updated sketch preprocessing validation to align with revised forward-declaration handling.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

Updates NXP LPC8xx toolchain flags in nxplpc.json to match ArduinoCore-LPC8xx recipe expectations (C++ standard gnu++11, -lc instead of -lc_nano, removed LTO/float-ABI/nostartfiles flags), adds corresponding unit and integration tests, adds #include <Arduino.h> to all LPC test fixtures, and overhauls the .ino preprocessor to preserve existing forward declarations and exclude setup/loop from auto-generated prototypes.

Changes

NXP LPC toolchain flag alignment

Layer / File(s)	Summary
NXP LPC build config flags crates/fbuild-build/src/nxplpc/configs/nxplpc.json	C++ standard changed from gnu++17 to gnu++11, linker_flags trimmed to --gc-sections only, -lc_nano replaced with -lc, and profiles.release drops LTO flags leaving only -Os.
Unit tests for updated compiler/linker flags crates/fbuild-build/src/nxplpc/mcu_config.rs	compiler_flags_target_cortex_m0plus asserts -std=gnu++11 present and -mfloat-abi=soft absent; new linker_flags_match_arduino_core_recipe test asserts -Wl,--gc-sections and -lc present, -nostartfiles and -lc_nano absent.
Integration test: compile_commands.json validation crates/fbuild-build/tests/nxplpc_core_compile_commands.rs	Ignored test builds lpc845brk with generate_compiledb: true, then inspects generated compile_commands.json to assert required and forbidden flags matching ArduinoCore recipe.
Add #include <Arduino.h> to LPC test fixtures tests/platform/lpc804/lpc804.ino, tests/platform/lpc845/lpc845.ino, tests/platform/lpc845brk/lpc845brk.ino, tests/platform/lpcxpresso804/lpcxpresso804.ino, tests/platform/lpcxpresso845max/lpcxpresso845max.ino, tests/platform/lpc845_build_flags/src/main.ino	All LPC platform test fixtures gain #include <Arduino.h>; main.ino additionally changes check_flag_no_op to extern "C" linkage.

.ino preprocessor: prototype and forward-declaration overhaul

Layer / File(s)	Summary
Source scanner: remove forward-decl stripping, skip entry-point prototypes crates/fbuild-build/src/source_scanner.rs	Removes the pipeline step that parsed and stripped existing forward declarations from concatenated sketch source; deletes find_existing_forward_declarations, collect_forward_declarations, and has_descendant_kind helpers; adds is_arduino_entry_point_signature to exclude setup/loop from auto-generated prototypes.
Source scanner tests for revised preprocessing crates/fbuild-build/src/source_scanner/tests.rs	Multi-.ino ordering tests switch from find to rfind for position checks; new assertions confirm setup/loop are absent from auto-generated prototypes; new test verifies user-provided forward declarations are preserved in output.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• FastLED/fbuild#570: Directly related — that PR introduced ArduinoCore-LPC8xx vendoring which drives the -lc vs -lc_nano and -nostartfiles linker expectations being tested here.
• FastLED/fbuild#657: Directly related — both PRs modify the .ino prototype/forward-declaration logic in source_scanner.rs, with #657 introducing tree-sitter parsing that this PR builds upon.
• FastLED/fbuild#763: Directly related — both PRs add #include <Arduino.h> to overlapping LPC platform .ino test fixtures.

Poem

🐇 Hop hop, the flags have changed today,
gnu++11 leads the way!
No more nano-libc small,
-lc now handles all.
setup and loop need no prototype cheer—
The rabbit refactored, the build path is clear! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 73.08% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title '[codex] Fix nxplpc Arduino core builds' directly addresses the main objective of fixing a build regression in nxplpc Arduino core builds, which is the primary focus of this changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/soldr-cross-compile-linux-x86

⚔️ Resolve merge conflicts

• Resolve merge conflict in branch ci/soldr-cross-compile-linux-x86

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