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Compiling code for Apple Silicon / M1 / ARM

Small projects/single files

	$ joe helloworld.c
	$ CC="/usr/bin/cc" CFLAGS="-target arm64-apple-macos11" cc helloworld.c -o helloworld

Bigger projects with autoconf

The issue: Standard ./configure / make will produce x86_64 binaries. We want ARM64 for Apple M1, Big Sur / macOS 11.0.1, XCode 12.2, Apple clang version 12.0.0 (clang-1200.0.32.27)

	$ cd src/ngircd-26
	$ make distclean

	$ CC="/usr/bin/cc" CFLAGS="-target arm64-apple-macos11" ./configure --host=aarch64-apple-darwin --target=aarch64-apple-darwin --build=aarch64-apple-darwin

The trick is, that we both convince configure and manually enforce compiler-choice and flags:

We want clang/LLVM, not gcc
CFLAGS="-target arm64-apple-macos11"
We want that target archicture for the C compiler
configure --host/--target/--build=aarch64-apple-darwin
autoconf should generate for these architecture choices. Note that the syntax/name for the arch is different here!
	$ make -j8

	$ file src/ngircd/ngircd
	src/ngircd/ngircd: Mach-O 64-bit executable arm64

	$ src/ngircd/ngircd --version
	ngIRCd 26-IRCPLUS+SYSLOG+ZLIB-aarch64/apple/darwin

Job done, we have M1/ARM64 binaries!