configure: set the bindgen cross target

Implement a bash version of rust-bindgen rust_to_clang_target() to
convert from rust target to clang target.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250924120426.2158655-8-marcandre.lureau@redhat.com>

configure

@@ -1878,6 +1878,13 @@ if test "$skip_meson" = no; then
       eval "c=\$devices_${a}"
       echo "${a}-softmmu = '$c'" >> $cross
   done
+  if test "$rust" != disabled; then
+      if test "$cross_compile" = "yes"; then
+          . "$source_path/scripts/rust-to-clang-target.sh"
+          clang_target=$(rust_to_clang_target "$rust_target_triple")
+          echo "bindgen_clang_arguments = [$(meson_quote --target="$clang_target")]" >> $cross
+      fi
+  fi
 
   echo "[built-in options]" >> $cross
   echo "c_args = [$(meson_quote $CFLAGS $EXTRA_CFLAGS)]" >> $cross

scripts/rust-to-clang-target-test.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env sh
+#
+# Copyright (C) 2025 Red Hat, Inc.
+#
+# Based on rust_to_clang_target() tests from rust-bindgen.
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+scripts_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+. "$scripts_dir/rust-to-clang-target.sh"
+
+test_case() {
+    input="$1"
+    expected="$2"
+    result=$(rust_to_clang_target "$input")
+
+    if [ "$result" = "$expected" ]; then
+        echo " OK: '$input' -> '$result'"
+    else
+        echo " FAILED: '$input'"
+        echo "  Expected: '$expected'"
+        echo "  Got:      '$result'"
+        exit 1
+    fi
+}
+
+echo "Running tests..."
+
+test_case "aarch64-apple-ios" "arm64-apple-ios"
+test_case "riscv64gc-unknown-linux-gnu" "riscv64-unknown-linux-gnu"
+test_case "riscv64imac-unknown-none-elf" "riscv64-unknown-none-elf"
+test_case "riscv32imc-unknown-none-elf" "riscv32-unknown-none-elf"
+test_case "riscv32imac-unknown-none-elf" "riscv32-unknown-none-elf"
+test_case "riscv32imafc-unknown-none-elf" "riscv32-unknown-none-elf"
+test_case "riscv32i-unknown-none-elf" "riscv32-unknown-none-elf"
+test_case "riscv32imc-esp-espidf" "riscv32-esp-elf"
+test_case "xtensa-esp32-espidf" "xtensa-esp32-elf"
+test_case "aarch64-apple-ios-sim" "arm64-apple-ios-simulator"
+test_case "aarch64-apple-tvos-sim" "arm64-apple-tvos-simulator"
+test_case "aarch64-apple-watchos-sim" "arm64-apple-watchos-simulator"
+
+echo ""
+echo "All tests passed!"

scripts/rust-to-clang-target.sh

@@ -0,0 +1,60 @@
+# Copyright (C) 2025 Red Hat, Inc.
+#
+# Based on rust_to_clang_target() from rust-bindgen.
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+rust_to_clang_target() {
+    rust_target="$1"
+
+    # Split the string by hyphens
+    triple_parts=""
+    old_IFS="$IFS"
+    IFS='-'
+    for part in $rust_target; do
+        triple_parts="$triple_parts $part"
+    done
+    IFS="$old_IFS"
+    set -- $triple_parts
+
+    # RISC-V
+    case "$1" in
+        riscv32*)
+            set -- "riscv32" "${2}" "${3}" "${4}"
+            ;;
+        riscv64*)
+            set -- "riscv64" "${2}" "${3}" "${4}"
+            ;;
+    esac
+
+    # Apple
+    if [ "$2" = "apple" ]; then
+        if [ "$1" = "aarch64" ]; then
+            set -- "arm64" "${2}" "${3}" "${4}"
+        fi
+        if [ "$4" = "sim" ]; then
+            set -- "${1}" "${2}" "${3}" "simulator"
+        fi
+    fi
+
+    # ESP-IDF
+    if [ "$3" = "espidf" ]; then
+        set -- "${1}" "${2}" "elf" "${4}"
+    fi
+
+    # Reassemble the string
+    new_triple=""
+    first=1
+    for part in "$@"; do
+        if [ -n "$part" ]; then
+            if [ "$first" -eq 1 ]; then
+                new_triple="$part"
+                first=0
+            else
+                new_triple="$new_triple-$part"
+            fi
+        fi
+    done
+
+    echo "$new_triple"
+}