Re: [PATCH v4 2/2] Makefile: support universal macOS builds via RUST_TARGETS
From: Patrick Steinhardt <hidden>
Date: 2026-07-06 10:49:48
On Sat, Jul 04, 2026 at 06:05:55PM +0000, Shardul Natu via GitGitGadget wrote:
From: Shardul Natu <redacted>
On macOS, Universal Binaries contain native executable code for
multiple architectures (such as Intel x86_64 and Apple Silicon arm64)
bundled into a single file. This is standard practice for macOS
distribution and CI packaging (such as internal distribution packages
or tooling like Burrito/Homebrew), allowing a single build artifact
to run natively across all Macs without Rosetta emulation or
maintaining separate packages.
When building Git C code for multiple architectures on macOS, the
Apple toolchain (clang) natively supports universal builds via
CFLAGS/LDFLAGS. When "-arch x86_64 -arch arm64" is passed, clang
automatically compiles and links universal binaries for all C object
files and executables out of the box.
Cargo and rustc, however, do not support multiple "-arch" flags or
emitting universal binaries in a single invocation. Instead, Cargo
requires invoking each target triple independently (e.g., passing
"--target x86_64-apple-darwin" and "--target aarch64-apple-darwin").
To bridge this gap when Rust is enabled:
1. Allow specifying space-separated target triples in RUST_TARGETS.
2. Introduce declarative pattern rules (target/%/...) to compile
each target-specific library slice via Cargo.
3. On macOS, if multiple targets are specified, use "lipo" (part of
the mandatory Xcode Command Line Tools) to combine the resulting
static libraries into target/release/libgitcore.a.
4. Ensure target directory creation before invoking lipo via
mkdir_p_parent_template.Nit: The last item really is quite uninteresting in the bigger scheme of things.
Once $(RUST_LIB) is compiled into a universal static archive, the standard C linker seamlessly links it with the C object files to produce universal Git executables.
Okay, this overall reads a lot better now.
quoted hunk ↗ jump to hunk
diff --git a/Makefile b/Makefile index 7db38ecce9..ecada0acb4 100644 --- a/Makefile +++ b/Makefile@@ -500,6 +500,14 @@ include shared.mak # # Building Rust code requires Cargo. # +# Define RUST_TARGETS if you want to cross-compile. If left unspecified, it uses +# the default rust target on the system.
s/rust/Rust/
quoted hunk ↗ jump to hunk
@@ -3022,8 +3031,30 @@ $(LIB_FILE): $(LIB_OBJS) $(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^ ifndef NO_RUST +ifeq ($(RUST_TARGETS),) $(RUST_LIB): Cargo.toml $(RUST_SOURCES) $(LIB_FILE) $(QUIET_CARGO)cargo build $(CARGO_ARGS) +else +ifneq ($(words $(RUST_TARGETS)),1) +ifneq ($(uname_S),Darwin) +$(error Building universal Rust libraries requires macOS (lipo is not available on $(uname_S))) +endif +endif + +RUST_MEMBER_LIBS = $(foreach target,$(RUST_TARGETS),target/$(target)/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME)) +$(RUST_MEMBER_LIBS): target/%/$(RUST_BUILD_CONFIG)/$(RUST_LIB_NAME): Cargo.toml $(RUST_SOURCES) $(LIB_FILE) + $(QUIET_CARGO)cargo build $(CARGO_ARGS) --target $*
With this we now have both:
- target/$ARCH/$BUILD_CONFIG/
- target/$BUILD_CONFIG/
Is there any reason why we have to have those two different layouts
instead of swapping the order in the first item so that all artifacts
are in "target/$BUILD_CONFIG/"? Essentially, what I'm proposing instead
is:
- "target/$BUILD_CONFIG/" for the final universal executable.
- "target/$BUILD_CONFIG/$ARCH" for the per-arch artifacts.
Patrick