Re: [PATCH v3 2/2] Makefile: support universal macOS builds via RUST_TARGETS

> > +$(RUST_LIB): $(RUST_MEMBER_LIBS)
> > + @$(call mkdir_p_parent_template)
>
> The leading @ is a bit curious because among ~20 existing use of
> this pattern, nobody adds it to squelch "mkdir -p". In fact, the
> macro uses the standard pattern to define $(QUIET_MKDIR_P_PARENT)
> that does the squelching when $(V) is unset.

> Recipe parts in our Makefile that are written in bourne shell, the
> CodingGuidelines apply.
>
> $ git grep -n -e 'if \[' ':(glob)**/Makefile'
>
> gives empty. Probably,
>
> if test $(words $(RUST_TARGETS)) -gt 1; \
> then \
>
> would fit better.

>
> "Shardul Natu via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Shardul Natu <snatu@google.com>
> >
> > 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").
>
> This is much easier to understand for those of us unfamiliar with
> the macOS ecosystem.  Very much appreciated.
>
> > +$(RUST_LIB): $(RUST_MEMBER_LIBS)
> > +     @$(call mkdir_p_parent_template)
>
> The leading @ is a bit curious because among ~20 existing use of
> this pattern, nobody adds it to squelch "mkdir -p".  In fact, the
> macro uses the standard pattern to define $(QUIET_MKDIR_P_PARENT)
> that does the squelching when $(V) is unset.
>
> > +     $(QUIET_GEN)\
> > +     if [ $(words $(RUST_TARGETS)) -gt 1 ]; then \
>
> Recipe parts in our Makefile that are written in bourne shell, the
> CodingGuidelines apply.
>
>     $ git grep -n -e 'if \[' ':(glob)**/Makefile'
>
> gives empty.  Probably,
>
>         if test $(words $(RUST_TARGETS)) -gt 1; \
>         then \
>
> would fit better.
>
> > +             lipo -create $^ -output $@; \
> > +     else \
> > +             cp $< $@; \
> > +     fi
> > +endif
> >
> >  .PHONY: rust
> >  rust: $(RUST_LIB)
>
> Other than that, looking good.
>
> Thanks.