使用CMake构建多Android NDK目标报错：could not load cache 求调试方法

尝试使用NDK构建多个ABI目标时，始终出现**"could not load cache"**错误，使用的是docker-android-ndk镜像，以及Monocypher提供的C源码。

错误信息 #

CMake Error: Could not load cache.
CMake Error: Error processing file: /app/CMakeLists.txt
ninja: error: rebuilding 'build.ninja': subcommand failed

构建脚本 #

#!/bin/bash
cd /app
cmake -GNinja -DCMAKE_TOOLCHAIN_FILE=$NDK_ROOT/build/cmake/android.toolchain.cmake -DANDROID_PLATFORM=android-21 /app 
cmake --build /app -v

CMakeLists.txt #

cmake_minimum_required(VERSION 3.16)
project(monocypher)

set(MONOCYPHER_SRC_FOLDER "Monocypher/src")

set(MONOCYPHER_SOURCES
    "${MONOCYPHER_SRC_FOLDER}/monocypher.h"
    "${MONOCYPHER_SRC_FOLDER}/monocypher.c"
    "${MONOCYPHER_SRC_FOLDER}/optional/monocypher-ed25519.h"
    "${MONOCYPHER_SRC_FOLDER}/optional/monocypher-ed25519.c"
)


include_directories(${MONOCYPHER_SRC_FOLDER})

include(ExternalProject)

file(TO_CMAKE_PATH "${CMAKE_TOOLCHAIN_FILE}" toolchain_file)


 macro (setup_library library_name android_abi)
    ExternalProject_Add(${library_name}-builder
      SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}"
      BUILD_ALWAYS YES
      DOWNLOAD_COMMAND ""
      INSTALL_COMMAND ""
      UPDATE_COMMAND ""
      PATCH_COMMAND ""
      CMAKE_ARGS
        -DLIBNAME=${library_name}
        -DANDROID_ABI=${android_abi}
        -DCMAKE_FIND_ROOT_PATH=${CMAKE_FIND_ROOT_PATH}
        -DCMAKE_PREFIX_PATH=${CMAKE_PREFIX_PATH}
        -DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}
        -DCMAKE_TOOLCHAIN_FILE=${toolchain_file}
        -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=${CMAKE_BINARY_DIR}/android-build/libs/${android_abi}
        -D${PROJECT_NAME}-MultiBuild=ON
      BUILD_COMMAND
        ${CMAKE_COMMAND} --build . --config Release
    )
   #add_library(monocypher_native SHARED ${MONOCYPHER_SOURCES})
   #set_property(TARGET monocypher_native PROPERTY ENABLE_EXPORTS 1)   
 endmacro()

 setup_library(${PROJECT_NAME}-v8a arm64-v8a ${CMAKE_PREFIX_PATH})

add_library(monocypher_native SHARED ${MONOCYPHER_SOURCES})
set_property(TARGET monocypher_native PROPERTY ENABLE_EXPORTS 1)

1. 解决ExternalProject缓存冲突 #

你用ExternalProject_Add直接将源码目录作为SOURCE_DIR，主CMake进程已在该目录生成CMakeCache.txt，子构建进程读取同一缓存时会引发冲突。

修改setup_library宏，给每个ABI指定独立构建目录：

macro (setup_library library_name android_abi)
    set(BUILD_DIR "${CMAKE_BINARY_DIR}/build-${android_abi}")
    ExternalProject_Add(${library_name}-builder
      SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}"
      BUILD_DIR "${BUILD_DIR}"  # 新增独立构建目录
      BUILD_ALWAYS YES
      DOWNLOAD_COMMAND ""
      INSTALL_COMMAND ""
      UPDATE_COMMAND ""
      PATCH_COMMAND ""
      CMAKE_ARGS
        -DLIBNAME=${library_name}
        -DANDROID_ABI=${android_abi}
        -DCMAKE_FIND_ROOT_PATH=${CMAKE_FIND_ROOT_PATH}
        -DCMAKE_PREFIX_PATH=${CMAKE_PREFIX_PATH}
        -DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}
        -DCMAKE_TOOLCHAIN_FILE=${toolchain_file}
        -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=${CMAKE_BINARY_DIR}/android-build/libs/${android_abi}
        -D${PROJECT_NAME}-MultiBuild=ON
      BUILD_COMMAND
        ${CMAKE_COMMAND} --build "${BUILD_DIR}" --config Release
    )
 endmacro()

2. 改用外部构建模式 #

原脚本直接在源码目录生成缓存，既污染源码也易引发冲突，改用Out-of-Source Build：

#!/bin/bash
mkdir -p /app/build && cd /app/build
cmake -GNinja -DCMAKE_TOOLCHAIN_FILE=$NDK_ROOT/build/cmake/android.toolchain.cmake -DANDROID_PLATFORM=android-21 .. 
cmake --build . -v

3. 验证CMake与NDK版本兼容性 #

docker镜像中的CMake版本可能不符合NDK要求，运行以下命令确认：

cmake --version
echo $NDK_ROOT && ls $NDK_ROOT/build/cmake/

例如NDK r25+要求CMake 3.22以上版本，版本不匹配时需更换镜像或升级CMake。

4. 清理残留缓存文件 #

每次构建前清理旧缓存，避免干扰：

rm -rf /app/CMakeCache.txt /app/CMakeFiles /app/build.ninja /app/build

5. 简化配置排查基础问题 #

暂时注释ExternalProject_Add相关代码，先验证单个ABI构建是否正常：

# include(ExternalProject)
# ...
# setup_library(...)

add_library(monocypher_native SHARED ${MONOCYPHER_SOURCES})
set_property(TARGET monocypher_native PROPERTY ENABLE_EXPORTS 1)

若单个ABI构建正常，再逐步定位ExternalProject的配置问题。

内容的提问来源于stack exchange，提问作者AlbertK