| // Helper program to generate trampoline scripts for NDK tools. |
| // |
| // This program is meant to be run by hand when making changes to the hermetic Android NDK |
| // toolchain, e.g. when upgrading to a new Android NDK version. |
| // |
| // Trampoline scripts are necessary because the `cc_common.create_cc_toolchain_config_info`[1] |
| // built-in Bazel function expects tool paths to point to files under the directory in which it is |
| // invoked, thus we cannot directly reference tools under `external/android_ndk`. The solution is |
| // to use trampoline scripts that pass through any command-line arguments to the NDK binaries under |
| // `external/android_sdk`. |
| // |
| // [1] https://bazel.build/rules/lib/cc_common#create_cc_toolchain_config_info |
| package main |
| |
| import ( |
| "errors" |
| "flag" |
| "fmt" |
| "os" |
| "path/filepath" |
| ) |
| |
| const bazelNdkPath = "external/android_ndk" |
| |
| // Paths relative to the Android NDK root directory. These paths can be determined by inspecting |
| // the Android NDK ZIP file downloaded by the `download_toolchains` macro defined in |
| // //toolchains/download_toolchains.bzl. |
| var tools = []string{ |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-ar", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-dwp", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-ld", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-nm", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-objcopy", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-objdump", |
| "toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-strip", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-ar", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-dwp", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-ld", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-nm", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objcopy", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump", |
| "toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-strip", |
| "toolchains/llvm/prebuilt/linux-x86_64/bin/clang", |
| } |
| |
| const trampolineScriptTemplate = `#!/bin/sh |
| %s $@ |
| ` |
| |
| func main() { |
| ndkDirFlag := flag.String("ndk-dir", "", "Path to a local copy of the NDK. Used only to verify that the tool paths assumed by this program are valid. Required.") |
| outDirFlag := flag.String("out-dir", "", "Directory where to save the trampoline scripts. Required.") |
| flag.Parse() |
| |
| if *ndkDirFlag == "" || *outDirFlag == "" { |
| flag.Usage() |
| os.Exit(1) |
| } |
| |
| for _, tool := range tools { |
| // Verify that the tool exists in the NDK. |
| ndkPath := filepath.Join(*ndkDirFlag, tool) |
| if _, err := os.Stat(ndkPath); errors.Is(err, os.ErrNotExist) { |
| fmt.Fprintf(os.Stderr, "File %s not found.", ndkPath) |
| os.Exit(1) |
| } |
| |
| // Generate trampoline script. |
| trampolineScript := fmt.Sprintf(trampolineScriptTemplate, filepath.Join(bazelNdkPath, tool)) |
| trampolineScriptPath := filepath.Join(*outDirFlag, filepath.Base(tool)+".sh") |
| if err := os.WriteFile(trampolineScriptPath, []byte(trampolineScript), 0750); err != nil { |
| fmt.Fprintf(os.Stderr, "Error writing file %s: %s", trampolineScriptPath, err) |
| } |
| } |
| } |
