Swift Cross Compile to Single Linux Binary

How to build a swift executable for Linux on macOS

This just means it couldn't locate the linked library. If your libswiftCore.so located at /usr/lib/swift/linux you can run LD_LIBRARY_PATH=/usr/lib/swift/linux ./<your executable for linux> and it will work like a charm.

You can also set LD_LIBRARY_PATH variable to just execute the binary.

Build Apple Silicon binary on Intel machine

We ended up solving solving this and being able to compile darwin-arm64 and debian-aarch64 binaries on GitHub Actions' x86-64 machines.

We pre-compiled all our dependencies for arm64 and linked them statically as well as dynamically.

export RELAY_DEPS_PATH=./build-deps/arm64
export PKG_CONFIG_PATH=./build-deps/arm64/lib/pkgconfig

cd ./relay-deps
TARGET=./build-deps make install

cd ./relay
phpize
./configure CFLAGS='-target arm64-apple-macos' \
  --host=aarch64-apple-darwin \
  --enable-relay-jemalloc-prefix
  [snip...]

make

# Dynamically linked binary
cc --target=arm64-apple-darwin \
  ${wl}-flat_namespace ${wl}-undefined ${wl}suppress \
  -o .libs/relay.so -bundle .libs/*.o \
  -L$RELAY_DEPS_PATH/lib -lhiredis -ljemalloc_pic [snip...]

# re-link to standard paths
./relay-deps/utils/macos/relink.sh .libs/relay.so /usr/local/lib
cp .libs/relay.so modules/relay.so

# Build a statically linked shared object
cc --target=arm64-apple-darwin \
  ${wl}-flat_namespace ${wl}-undefined ${wl}suppress \
  -o .libs/relay-static.so -bundle .libs/*.o \
  $RELAY_DEPS_PATH/lib/libhiredis.a \
  $RELAY_DEPS_PATH/lib/libjemalloc_pic.a \
  [snip...]

The relink.sh:

#!/bin/bash
set -e

printUsage() {
    echo "$0 <shared-object> <prefix>"
    exit 1
}

if [[ ! -f "$1" || -z "$2" ]]; then
    printUsage
    exit 1
fi

INFILE=$1
PREFIX=$2

links=(libjemalloc libhiredis [snip...])

if [ -z "$PREFIX" ]; then
    PREFIX=libs
fi

for link in ${links[@]}; do
    FROM=$(otool -L "$INFILE"|grep $link|awk '{print $1}')
    FILE=$(basename -- "$FROM")
    TO="$PREFIX/$FILE"

    echo "$FROM -> $TO"
    install_name_tool -change "$FROM" "$TO" "$1"
done

Is a Linux executable compatible with OS X?

No, Linux and Mac OS X binaries are not cross-compatible.

For one thing, Linux executables use a format called ELF.

Mac OS X executables use Mach-O format.

Thus, even if a lot of the libraries ordinarily compile separately on each system, they would not be portable in binary format.

Furthermore, Linux is not actually UNIX-based. It does share a number of common features and tools with UNIX, but a lot of that has to do with computing standards like POSIX.

All this said, people can and do create pretty cool ways to deal with the problem of cross-compatibility.

EDIT:

Finally, to address your point on byte-code: when making a binary, compilers usually generate machine code that is specific to the platform you're developing on. (This isn't always the case, but it usually is.)

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