Re: [RFC PATCH v3 1/5] build-sys: Add rust feature option

[Manos Pitsidianakis <manos.pitsidianakis@linaro.org>]

On Thu, 20 Jun 2024 16:21, Paolo Bonzini <pbonzini@redhat.com> wrote:
>On 6/19/24 22:13, Manos Pitsidianakis wrote:
>> 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.
>> 
>> A cargo_wrapper.py script is added that is heavily based on the work of
>> Marc-André Lureau from 2021.
>> 
>> https://patchew.org/QEMU/20210907121943.3498701-1-marcandre.lureau@redhat.com/
>> 
>> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
>
>The cargo_wrapper.py script is not used yet, so it should be
>delayed until it's used.

That's true, I just wanted to make review easier by splitting it out. 
Can we squash them later or do you think I should I do it for the next 
series version?



>
>For the detection of the toolchain, I'd rather do everything in
>configure since that's where the cross file is built.  Something like:
>
>diff --git a/configure b/configure
>index 8b6a2f16ceb..6412a1021c3 100755
>--- a/configure
>+++ b/configure
>@@ -173,6 +173,8 @@ fi
>  
>  # default parameters
>  container_engine="auto"
>+rust_target_triple=""
>+with_rust="no"
>  cpu=""
>  cross_compile="no"
>  cross_prefix=""
>@@ -201,6 +202,8 @@ for opt do
>    --cross-prefix=*) cross_prefix="$optarg"
>                      cross_compile="yes"
>    ;;
>+  --cargo=*) CARGO="$optarg"
>+  ;;
>    --cc=*) CC="$optarg"
>    ;;
>    --cxx=*) CXX="$optarg"
>@@ -317,6 +322,8 @@ windmc="${WINDMC-${cross_prefix}windmc}"
>  pkg_config="${PKG_CONFIG-${cross_prefix}pkg-config}"
>  sdl2_config="${SDL2_CONFIG-${cross_prefix}sdl2-config}"
>  
>+cargo="${CARGO-cargo}"
>+
>  check_define() {
>  cat > $TMPC <<EOF
>  #if !defined($1)
>@@ -628,6 +635,8 @@ for opt do
>    ;;
>    --cross-prefix=*)
>    ;;
>+  --cargo=*)
>+  ;;
>    --cc=*)
>    ;;
>    --host-cc=*) host_cc="$optarg"
>@@ -755,8 +764,14 @@ for opt do
>    ;;
>    --container-engine=*) container_engine="$optarg"
>    ;;
>+  --rust-target-triple=*) rust_target_triple="$optarg"
>+  ;;
>    --gdb=*) gdb_bin="$optarg"
>    ;;
>+  --with-rust) with_rust=yes
>+  ;;
>+  --without-rust) with_rust=no
>+  ;;
>    # everything else has the same name in configure and meson
>    --*) meson_option_parse "$opt" "$optarg"
>    ;;
>@@ -854,6 +869,7 @@ $(echo Available targets: $default_target_list | \
>  Advanced options (experts only):
>    -Dmesonoptname=val       passthrough option to meson unmodified
>    --cross-prefix=PREFIX    use PREFIX for compile tools, PREFIX can be blank [$cross_prefix]
>+  --cargo=CARGO            use Cargo binary CARGO [$cargo]
>    --cc=CC                  use C compiler CC [$cc]
>    --host-cc=CC             when cross compiling, use C compiler CC for code run
>                             at build time [$host_cc]
>@@ -869,11 +885,13 @@ Advanced options (experts only):
>    --python=PYTHON          use specified python [$python]
>    --ninja=NINJA            use specified ninja [$ninja]
>    --static                 enable static build [$static]
>-  --without-default-features default all --enable-* options to "disabled"
>-  --without-default-devices  do not include any device that is not needed to
>+  --rust-target-triple=TRIPLE  target for Rust cross compilation
>+  --without-default-features   default all --enable-* options to "disabled"
>+  --without-default-devices    do not include any device that is not needed to
>                             start the emulator (only use if you are including
>                             desired devices in configs/devices/)
>    --with-devices-ARCH=NAME override default configs/devices
>+  --with-rust              enable experimental Rust code
>    --enable-debug           enable common debug build options
>    --cpu=CPU                Build for host CPU [$cpu]
>    --disable-containers     don't use containers for cross-building
>@@ -1138,6 +1159,20 @@ EOF
>    fi
>  fi
>  
>+##########################################
>+# detect rust triples
>+
>+if test "$with_rust" = yes; then
>+  $CARGO -vV > "${TMPDIR1}/${TMPB}.out"
>+  if test $? != 0; then
>+    error_exit "could not execute cargo binary \"$CARGO\""
>+  fi
>+  rust_host_triple=$(sed -n 's/^host: //p' "${TMPDIR1}/${TMPB}.out")
>+  if test "$rust_target_triple" = ""; then
>+    rust_target_triple=$rust_host_triple
>+  fi
>+fi
>+
>  ##########################################
>  # functions to probe cross compilers
>  
>@@ -1604,6 +1639,10 @@ if test "$container" != no; then
>      echo "RUNC=$runc" >> $config_host_mak
>  fi
>  echo "SUBDIRS=$subdirs" >> $config_host_mak
>+if test "$with_rust" = yes; then
>+  echo "RUST_HOST_TRIPLE=$rust_host_triple" >> $config_host_mak
>+  echo "RUST_TARGET_TRIPLE=$rust_target_triple" >> $config_host_mak
>+fi
>  echo "PYTHON=$python" >> $config_host_mak
>  echo "MKVENV_ENSUREGROUP=$mkvenv ensuregroup $mkvenv_online_flag" >> $config_host_mak
>  echo "GENISOIMAGE=$genisoimage" >> $config_host_mak
>@@ -1731,6 +1770,13 @@ if test "$skip_meson" = no; then
>    echo "c = [$(meson_quote $cc $CPU_CFLAGS)]" >> $cross
>    test -n "$cxx" && echo "cpp = [$(meson_quote $cxx $CPU_CFLAGS)]" >> $cross
>    test -n "$objcc" && echo "objc = [$(meson_quote $objcc $CPU_CFLAGS)]" >> $cross
>+  if test "$with_rust" = yes; then
>+    if test "$rust_host_triple" != "$rust_target_triple"; then
>+      echo "cargo = [$(meson_quote $cargo --target "$rust_target_triple")]" >> $cross
>+    else
>+      echo "cargo = [$(meson_quote $cargo)]" >> $cross
>+    fi
>+  fi


Hm that looks better indeed, thanks!


>    echo "ar = [$(meson_quote $ar)]" >> $cross
>    echo "dlltool = [$(meson_quote $dlltool)]" >> $cross
>    echo "nm = [$(meson_quote $nm)]" >> $cross
>diff --git a/meson.build b/meson.build
>index c5360fbd299..ad7dbc0d641 100644
>--- a/meson.build
>+++ b/meson.build
>@@ -290,6 +290,11 @@ foreach lang : all_languages
>    endif
>  endforeach
>  
>+cargo = not_found
>+if 'RUST_TARGET_TRIPLE' in config_host
>+  cargo = find_program('cargo', required: true)
>+endif
>+
>  # 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
>@@ -4239,6 +4244,10 @@ if 'objc' in all_languages
>  else
>    summary_info += {'Objective-C compiler': false}
>  endif
>+summary_info += {'Rust support':      cargo.found()}
>+if cargo.found() and config_host['RUST_TARGET_TRIPLE']) != config_host['RUST_HOST_TRIPLE']
>+  summary_info += {'Rust target':     config_host['RUST_TARGET_TRIPLE']}
>+endif
>  option_cflags = (get_option('debug') ? ['-g'] : [])
>  if get_option('optimization') != 'plain'
>    option_cflags += ['-O' + get_option('optimization')]
>
>