Re: [RFC PATCH v3 2/5] rust: add bindgen step as a meson dependency

["Alex Bennée" <alex.bennee@linaro.org>]

Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:

> Add mechanism to generate rust hw targets that depend on a custom
> bindgen target for rust bindings to C.
>
> This way bindings will be created before the rust crate is compiled.
>
> The bindings will end up in BUILDDIR/{target}-generated.rs and have the same name
> as a target:
>
> ninja aarch64-softmmu-generated.rs
>
<snip>
> +
> +
> +rust_targets = {}
> +
> +cargo_wrapper = [
> +  find_program(meson.global_source_root() / 'scripts/cargo_wrapper.py'),
> +  '--config-headers', meson.project_build_root() / 'config-host.h',
> +  '--meson-build-root', meson.project_build_root(),
> +  '--meson-build-dir', meson.current_build_dir(),
> +  '--meson-source-dir', meson.current_source_dir(),
> +]

I'm unclear what the difference between meson-build-root and
meson-build-dir is?

We also end up defining crate-dir and outdir. Aren't these all
derivable from whatever module we are building?

> +
> +if get_option('b_colorout') != 'never'
> +  cargo_wrapper += ['--color', 'always']
> +endif
> +
> +if get_option('optimization') in ['0', '1', 'g']
> +  rs_build_type = 'debug'
> +else
> +  rs_build_type = 'release'
> +endif
> +
> +# Collect metadata for each (crate,qemu-target,compiler-target) combination.
> +# Rust meson targets cannot be defined a priori because they depend on bindgen
> +# generation that is created for each emulation target separately. Thus Rust
> +# meson targets will be defined for each target after the target-specific
> +# bindgen dependency is declared.
> +rust_hw_target_list = {}
> +
> +foreach rust_hw_target, rust_hws: rust_hw_target_list
> +  foreach rust_hw_dev: rust_hws
> +    output = meson.current_build_dir() / rust_target_triple / rs_build_type / rust_hw_dev['output']
> +    crate_metadata = {
> +      'name': rust_hw_dev['name'],
> +      'output': [rust_hw_dev['output']],
> +      'output-path': output,
> +      'command': [cargo_wrapper,
> +        '--crate-dir', meson.current_source_dir() / rust_hw_dev['dirname'],
> +        '--profile', rs_build_type,
> +        '--target-triple', rust_target_triple,
> +        '--outdir', '@OUTDIR@',
> +        'build-lib'
> +        ]
> +      }
> +    rust_targets += { rust_hw_target: [crate_metadata] }
> +  endforeach
> +endforeach
> diff --git a/rust/wrapper.h b/rust/wrapper.h
> new file mode 100644
> index 0000000000..bcf808c8d7
> --- /dev/null
> +++ b/rust/wrapper.h
> @@ -0,0 +1,39 @@
> +/*
> + * QEMU System Emulator
> + *
> + * Copyright (c) 2003-2020 Fabrice Bellard
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/module.h"
> +#include "qemu-io.h"
> +#include "sysemu/sysemu.h"
> +#include "hw/sysbus.h"
> +#include "exec/memory.h"
> +#include "chardev/char-fe.h"
> +#include "hw/clock.h"
> +#include "hw/qdev-clock.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/qdev-properties-system.h"
> +#include "hw/irq.h"
> +#include "qapi/error.h"
> +#include "migration/vmstate.h"
> +#include "chardev/char-serial.h"
> diff --git a/scripts/cargo_wrapper.py b/scripts/cargo_wrapper.py
> index 927336f80e..833e0e55f8 100644
> --- a/scripts/cargo_wrapper.py
> +++ b/scripts/cargo_wrapper.py
> @@ -111,6 +111,8 @@ def get_cargo_rustc(args: argparse.Namespace) -> tuple[Dict[str, Any], List[str]
>  
>      env = os.environ
>      env["CARGO_ENCODED_RUSTFLAGS"] = cfg
> +    env["MESON_BUILD_DIR"] = str(target_dir)
> +    env["MESON_BUILD_ROOT"] = str(args.meson_build_root)
>  
>      return (env, cargo_cmd)
>  
> @@ -234,6 +236,14 @@ def main() -> None:
>          required=True,
>      )
>      parser.add_argument(
> +        "--meson-build-root",
> +        metavar="BUILD_ROOT",
> +        help="meson.project_build_root()",
> +        type=Path,
> +        dest="meson_build_root",
> +        required=True,
> +    )
> +    parser.add_argument(
>          "--meson-source-dir",
>          metavar="SOURCE_DIR",
>          help="meson.current_source_dir()",

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro