[RFC PATCH v1 1/6] build-sys: Add rust feature option

[Manos Pitsidianakis]

Add options for Rust in meson_options.txt, meson.build, configure to
prepare for adding Rust code in the followup commits.

`rust` is a reserved meson name, so we have to use an alternative.
`with_rust` was chosen.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
The cargo wrapper script hardcodes some rust target triples. This is 
just temporary.
---
 .gitignore               |   2 +
 configure                |  12 +++
 meson.build              |  11 ++
 meson_options.txt        |   4 +
 scripts/cargo_wrapper.py | 211 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 240 insertions(+)
 create mode 100644 scripts/cargo_wrapper.py

diff --git a/.gitignore b/.gitignore
index 61fa39967b..f42b0d937e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,8 @@
 /build/
 /.cache/
 /.vscode/
+/target/
+rust/**/target
 *.pyc
 .sdk
 .stgit-*
diff --git a/configure b/configure
index 38ee257701..c195630771 100755
--- a/configure
+++ b/configure
@@ -302,6 +302,9 @@ else
   objcc="${objcc-${cross_prefix}clang}"
 fi
 
+with_rust="auto"
+with_rust_target_triple=""
+
 ar="${AR-${cross_prefix}ar}"
 as="${AS-${cross_prefix}as}"
 ccas="${CCAS-$cc}"
@@ -760,6 +763,12 @@ for opt do
   ;;
   --gdb=*) gdb_bin="$optarg"
   ;;
+  --enable-rust) with_rust=enabled
+  ;;
+  --disable-rust) with_rust=disabled
+  ;;
+  --rust-target-triple=*) with_rust_target_triple="$optarg"
+  ;;
   # everything else has the same name in configure and meson
   --*) meson_option_parse "$opt" "$optarg"
   ;;
@@ -1796,6 +1805,9 @@ if test "$skip_meson" = no; then
   test -n "${LIB_FUZZING_ENGINE+xxx}" && meson_option_add 
"-Dfuzzing_engine=$LIB_FUZZING_ENGINE"
   test "$plugins" = yes && meson_option_add "-Dplugins=true"
   test "$tcg" != enabled && meson_option_add "-Dtcg=$tcg"
+  test "$with_rust" != enabled && meson_option_add "-Dwith_rust=$with_rust"
+  test "$with_rust" != enabled && meson_option_add "-Dwith_rust=$with_rust"
+  test "$with_rust_target_triple" != "" && meson_option_add 
"-Dwith_rust_target_triple=$with_rust_target_triple"
   run_meson() {
     NINJA=$ninja $meson setup "$@" "$PWD" "$source_path"
   }
diff --git a/meson.build b/meson.build
index a9de71d450..3533889852 100644
--- a/meson.build
+++ b/meson.build
@@ -290,6 +290,12 @@ foreach lang : all_languages
   endif
 endforeach
 
+cargo = not_found
+if get_option('with_rust').allowed()
+  cargo = find_program('cargo', required: get_option('with_rust'))
+endif
+with_rust = cargo.found()
+
 # default flags for all hosts
 # We use -fwrapv to tell the compiler that we require a C dialect where
 # left shift of signed integers is well defined and has the expected
@@ -2066,6 +2072,7 @@ endif
 
 config_host_data = configuration_data()
 
+config_host_data.set('CONFIG_WITH_RUST', with_rust)
 audio_drivers_selected = []
 if have_system
   audio_drivers_available = {
@@ -4190,6 +4197,10 @@ if 'objc' in all_languages
 else
   summary_info += {'Objective-C compiler': false}
 endif
+summary_info += {'Rust support':      with_rust}
+if with_rust and get_option('with_rust_target_triple') != ''
+  summary_info += {'Rust target':     get_option('with_rust_target_triple')}
+endif
 option_cflags = (get_option('debug') ? ['-g'] : [])
 if get_option('optimization') != 'plain'
   option_cflags += ['-O' + get_option('optimization')]
diff --git a/meson_options.txt b/meson_options.txt
index 4c1583eb40..223491b731 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -366,3 +366,7 @@ option('qemu_ga_version', type: 'string', value: '',
 
 option('hexagon_idef_parser', type : 'boolean', value : true,
        description: 'use idef-parser to automatically generate TCG code for 
the Hexagon frontend')
+option('with_rust', type: 'feature', value: 'auto',
+       description: 'Enable Rust support')
+option('with_rust_target_triple', type : 'string', value: '',
+       description: 'Rust target triple')
diff --git a/scripts/cargo_wrapper.py b/scripts/cargo_wrapper.py
new file mode 100644
index 0000000000..d338effdaa
--- /dev/null
+++ b/scripts/cargo_wrapper.py
@@ -0,0 +1,211 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020 Red Hat, Inc.
+# Copyright (c) 2023 Linaro Ltd.
+#
+# Authors:
+#  Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+#  Marc-André Lureau <marcandre.lureau@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or
+# later.  See the COPYING file in the top-level directory.
+
+import argparse
+import configparser
+import distutils.file_util
+import json
+import logging
+import os
+import os.path
+import re
+import subprocess
+import sys
+import pathlib
+import shutil
+import tomllib
+
+from pathlib import Path
+from typing import Any, Dict, List, Tuple
+
+RUST_TARGET_TRIPLES = (
+    "aarch64-unknown-linux-gnu",
+    "x86_64-unknown-linux-gnu",
+    "x86_64-apple-darwin",
+    "aarch64-apple-darwin",
+)
+
+
+def cfg_name(name: str) -> str:
+    if (
+        name.startswith("CONFIG_")
+        or name.startswith("TARGET_")
+        or name.startswith("HAVE_")
+    ):
+        return name
+    return ""
+
+
+def generate_cfg_flags(header: str) -> List[str]:
+    with open(header, encoding="utf-8") as cfg:
+        config = [l.split()[1:] for l in cfg if l.startswith("#define")]
+
+    cfg_list = []
+    for cfg in config:
+        name = cfg_name(cfg[0])
+        if not name:
+            continue
+        if len(cfg) >= 2 and cfg[1] != "1":
+            continue
+        cfg_list.append("--cfg")
+        cfg_list.append(name)
+    return cfg_list
+
+
+def cargo_target_dir(args: argparse.Namespace) -> pathlib.Path:
+    return args.meson_build_dir
+
+
+def manifest_path(args: argparse.Namespace) -> pathlib.Path:
+    return args.crate_dir / "Cargo.toml"
+
+
+def get_cargo_rustc(args: argparse.Namespace) -> tuple[Dict[str, Any], 
List[str]]:
+    # See https://doc.rust-lang.org/cargo/reference/environment-variables.html
+    # Item `CARGO_ENCODED_RUSTFLAGS — A list of custom flags separated by
+    # 0x1f (ASCII Unit Separator) to pass to all compiler invocations that 
Cargo
+    # performs`
+    cfg = chr(0x1F).join(
+        [c for h in args.config_headers for c in generate_cfg_flags(h)]
+    )
+    target_dir = cargo_target_dir(args)
+    cargo_path = manifest_path(args)
+
+    cargo_cmd = [
+        "cargo",
+        "build",
+        "--target-dir",
+        str(target_dir),
+        "--manifest-path",
+        str(cargo_path),
+    ]
+    if args.target_triple:
+        cargo_cmd += ["--target", args.target_triple]
+    if args.profile == "release":
+        cargo_cmd += ["--release"]
+
+    env = os.environ
+    env["CARGO_ENCODED_RUSTFLAGS"] = cfg
+
+    return (env, cargo_cmd)
+
+
+def run_cargo(env: Dict[str, Any], cargo_cmd: List[str]) -> str:
+    envlog = " ".join(["{}={}".format(k, v) for k, v in env.items()])
+    cmdlog = " ".join(cargo_cmd)
+    logging.debug("Running %s %s", envlog, cmdlog)
+    try:
+        out = subprocess.check_output(
+            cargo_cmd,
+            env=dict(os.environ, **env),
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+        )
+    except subprocess.CalledProcessError as err:
+        print("Environment: " + envlog)
+        print("Command: " + cmdlog)
+        print(err.output)
+        sys.exit(1)
+
+    return out
+
+
+def build_lib(args: argparse.Namespace) -> None:
+    logging.debug("build-lib")
+    target_dir = cargo_target_dir(args)
+    cargo_toml_path = manifest_path(args)
+
+    with open(cargo_toml_path, "rb") as f:
+        config = tomllib.load(f)
+
+    package_name = config["package"]["name"].strip('"').replace("-", "_")
+
+    liba_filename = "lib" + package_name + ".a"
+    liba = target_dir / args.target_triple / args.profile / liba_filename
+
+    env, cargo_cmd = get_cargo_rustc(args)
+    out = run_cargo(env, cargo_cmd)
+    logging.debug("cp %s %s", liba, args.outdir)
+    shutil.copy2(liba, args.outdir)
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-v", "--verbose", action="store_true")
+    parser.add_argument(
+        "--color",
+        metavar="WHEN",
+        choices=["auto", "always", "never"],
+        default="auto",
+        help="Coloring: auto, always, never",
+    )
+    parser.add_argument(
+        "--config-headers",
+        metavar="CONFIG_HEADER",
+        action="append",
+        dest="config_headers",
+        required=False,
+        default=[],
+    )
+    parser.add_argument(
+        "--meson-build-dir",
+        metavar="BUILD_DIR",
+        help="meson.current_build_dir()",
+        type=pathlib.Path,
+        dest="meson_build_dir",
+        required=True,
+    )
+    parser.add_argument(
+        "--meson-source-dir",
+        metavar="SOURCE_DIR",
+        help="meson.current_source_dir()",
+        type=pathlib.Path,
+        dest="meson_source_dir",
+        required=True,
+    )
+    parser.add_argument(
+        "--crate-dir",
+        metavar="CRATE_DIR",
+        type=pathlib.Path,
+        dest="crate_dir",
+        help="Absolute path that contains the manifest file of the crate to 
compile",
+        required=True,
+    )
+    parser.add_argument(
+        "--outdir",
+        metavar="OUTDIR",
+        type=pathlib.Path,
+        dest="outdir",
+        help="Path to copy compiled artifacts to for Meson to use.",
+        required=True,
+    )
+    parser.add_argument(
+        "--profile", type=str, choices=["release", "debug"], required=True
+    )
+    parser.add_argument(
+        "--target-triple", type=str, choices=RUST_TARGET_TRIPLES, required=True
+    )
+
+    subparsers = parser.add_subparsers()
+
+    buildlib = subparsers.add_parser("build-lib")
+    buildlib.set_defaults(func=build_lib)
+
+    args = parser.parse_args()
+    if args.verbose:
+        logging.basicConfig(level=logging.DEBUG)
+    logging.debug("args: %s", args)
+
+    args.func(args)
+
+
+if __name__ == "__main__":
+    main()
-- 
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