build(darwin): add macOS arm64 support with VideoToolbox#10
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flexiondotorg merged 3 commits intomainfrom Jan 14, 2026
Merged
build(darwin): add macOS arm64 support with VideoToolbox#10flexiondotorg merged 3 commits intomainfrom
flexiondotorg merged 3 commits intomainfrom
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Resolve three blocking issues for building FFmpeg and 20 dependencies on macOS arm64 within Nix development environment: - Force clang compiler via FFmpeg configure flags and build environment - Disable x264 assembly on Apple Silicon (GNU macro incompatibility with LLVM) - Build rav1e without git_version feature to avoid libgit2/libiconv dependency - Configure C++ header search order with -nostdinc++ and explicit libc++ path - Filter NIX_CFLAGS_COMPILE to prevent incorrect -isystem injection - Use Apple's /usr/bin/libtool instead of GNU libtool for library combining - Add VideoToolbox hardware encoder support (H.264, HEVC, ProRes) - Export LIBCXX_INCLUDE from flake.nix for C++ dependency builds Root cause: Nix dev shell provides both GCC and Clang, but CGO_CFLAGS points to Clang's builtin headers containing preprocessor features (__has_feature, __building_module) that GCC doesn't recognise. Verified: All 17 platform-applicable libraries build successfully, combine into lib/darwin_arm64/libffmpeg.a (63MB), tests pass, VideoToolbox encoders confirmed present. Signed-off-by: Martin Wimpress <martin@wimpress.org>
x264's aarch64 .S files contain macros (T(), const, endconst) requiring C preprocessor expansion. The bare 'as' command skips preprocessing, causing build failures. Setting AS=clang ensures preprocessing runs before assembly, matching Apple's Xcode toolchain behaviour. Removes the --disable-asm workaround that caused 10-20% performance loss. Signed-off-by: Martin Wimpress <martin@wimpress.org>
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1 issue found across 6 files
Prompt for AI agents (all issues)
Check if these issues are valid — if so, understand the root cause of each and fix them.
<file name="internal/builder/library.go">
<violation number="1" location="internal/builder/library.go:300">
P2: LIBRARY_PATH handling is inconsistent with other environment variables. This unconditionally appends without checking for an existing value, potentially creating duplicate environment variables and losing existing paths that cargo/rustc might depend on.</violation>
</file>
Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.
Follow same pattern as LDFLAGS/CFLAGS handling - check for existing value and prepend rather than overwrite, preventing loss of paths that cargo/rustc might depend on.
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Summary
Enable FFmpeg and 20 dependencies to build on macOS arm64 within the Nix development environment, with full x264 assembly optimisation and VideoToolbox hardware encoder support.
Changes
AS=clangfor x264 on arm64 to ensure C preprocessor expands assembly macrosgit_versionfeature to avoid libgit2/libiconv dependency-nostdinc++and explicit libc++ pathNIX_CFLAGS_COMPILEto prevent incorrect-isysteminjection/usr/bin/libtoolinstead of GNU libtool for library combiningLIBCXX_INCLUDEfrom flake.nix for C++ dependency buildsRoot Cause
Nix dev shell provides both GCC and Clang, but
CGO_CFLAGSpoints to Clang's builtin headers containing preprocessor features (__has_feature,__building_module) that GCC doesn't recognise. Additionally, x264's aarch64 assembly uses macros requiring C preprocessor expansion, which the bareascommand skips.Testing
lib/darwin_arm64/libffmpeg.a(63MB)Known Limitations
just generaterequires Linux (go-clang bindings incompatible with macOS libclang blocks)