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Fix macOS/unix desktop build with newer Clang (17+)#103

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ThomasFarstrike merged 2 commits into
MicroPythonOS:mainfrom
bitcoin3us:fix/macos-clang-build-warnings
Mar 31, 2026
Merged

Fix macOS/unix desktop build with newer Clang (17+)#103
ThomasFarstrike merged 2 commits into
MicroPythonOS:mainfrom
bitcoin3us:fix/macos-clang-build-warnings

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@bitcoin3us bitcoin3us commented Mar 30, 2026

Summary

  • Modern Clang (17+, shipped with Xcode 15+) treats -Wgnu-folding-constant and -Wmissing-field-initializers as errors under -Werror, breaking the desktop build
  • build_mpos.sh now temporarily patches the unix Makefile CWARN to suppress these warnings, then restores after build
  • Follows the same pattern already used for the @micropython.viper decorator

Errors fixed

py/emitnative.c: error: variable length array folded to constant array [-Werror,-Wgnu-folding-constant]
lcd_bus/modlcd_bus.c: error: missing field 'defval' initializer [-Werror,-Wmissing-field-initializers]

Test plan

  • Run scripts/build_mpos.sh macOS on macOS with Xcode 15+ (Clang 17+)
  • Verify build completes successfully
  • Verify Makefile is restored after build

🤖 Generated with Claude Code

@claude
Fix macOS/unix desktop build with newer Clang (17+)
2f19b4f 
Modern Clang treats -Wgnu-folding-constant and
-Wmissing-field-initializers as errors under -Werror, breaking
the desktop build. Temporarily suppress these warnings during
the build, matching the existing pattern for the viper decorator.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
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ThomasFarstrike commented Mar 30, 2026

Awesome!

I guess the only thing to do is make sure the fix is not applied for the Linux builds, or somehow limit it, because now those failed with:

cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-bitwise-instead-of-logical’ may have been intended to silence earlier diagnostics
cc1: error: ‘-Wno-error=gnu-folding-constant’: no option ‘-Wgnu-folding-constant’
cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-bitwise-instead-of-logical’ may have been intended to silence earlier diagnostics
cc1: error: ‘-Wno-error=gnu-folding-constant’: no option ‘-Wgnu-folding-constant’
cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-bitwise-instead-of-logical’ may have been intended to silence earlier diagnostics
cc1: error: ‘-Wno-error=gnu-folding-constant’: no option ‘-Wgnu-folding-constant’
cc1: note: unrecognized command-line option ‘-Wno-unused-command-line-argument’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-bitwise-instead-of-logical’ may have been intended to silence earlier diagnostics
make: *** [../../py/mkrules.mk:133: build-standard/genhdr/qstr.i.last] Error 1

@claude
Only apply Clang warning suppression on macOS, not Linux
a63cb9c 
GCC on Linux doesn't have -Wgnu-folding-constant, so applying
these flags breaks the Linux build. Guard the Makefile patch
with a Darwin check so it only runs on macOS.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>
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bitcoin3us commented Mar 30, 2026

Good catch — GCC doesn't have -Wgnu-folding-constant. Updated to only apply the warning suppression on macOS (uname -s = Darwin), leaving Linux builds untouched.

@ThomasFarstrike ThomasFarstrike merged commit 8a6ff0f into MicroPythonOS:main Mar 31, 2026
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@bitcoin3us @ThomasFarstrike