c++ - 如何避免使用 CMake FetchContent 进行更新检查？

Question

全部。
我决定使用新的 cmake 宏来下载外部依赖项。
我从 Catch2 库的文档中获取了示例代码。

include(FetchContent)

FetchContent_Declare(
    Catch2
    GIT_REPOSITORY https://github.com/catchorg/Catch2.git
    GIT_TAG        v2.13.4
)
FetchContent_GetProperties(Catch2)
if(NOT Catch2_POPULATED)
    FetchContent_Populate(Catch2)
    add_subdirectory(${catch2_SOURCE_DIR} ${catch2_BINARY_DIR})
endif()

该解决方案效果很好，除了能够在我离线时重新启动 cmake(没有 wifi 和移动网络，只有我和我的笔记本电脑)。
我收到以下错误:

[0/7] Performing update step for 'catch2-populate'
fatal: «https://github.com/catchorg/Catch2.git/» недоступно: Could not resolve host: github.com
CMake Error at /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-subbuild/catch2-populate-prefix/tmp/catch2-populate-gitupdate.cmake:97 (execute_process):
  execute_process failed command indexes:

    1: "Child return code: 128"

FAILED: catch2-populate-prefix/src/catch2-populate-stamp/catch2-populate-update 
cd /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-src && /usr/local/Cellar/cmake/3.20.1/bin/cmake -P /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-subbuild/catch2-populate-prefix/tmp/catch2-populate-gitupdate.cmake
ninja: build stopped: subcommand failed.

CMake Error at /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1012 (message):
  Build step for catch2 failed: 1
Call Stack (most recent call first):
  /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1141:EVAL:2 (__FetchContent_directPopulate)
  /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1141 (cmake_language)
  /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1184 (FetchContent_Populate)
  .cmake/icmake.cmake:46 (FetchContent_MakeAvailable)
  CMakeLists.txt:10 (include)

-- Configuring incomplete, errors occurred!

是否可以一次下载依赖项，检查版本并且不要每次都尝试连接到远程服务器？

Answer 1

FetchContent_Populate 的 documentation 表示您可以使用 FETCHCONTENT_UPDATES_DISCONNECTED 缓存变量获得您想要的内容:

FETCHCONTENT_UPDATES_DISCONNECTED

... This ... disables theupdate stage. Therefore, if content has not been downloadedpreviously, it will still be downloaded when this option is enabled.This can speed up the configure stage... It is OFF by default.

因此，将其全局设置为 ON ，或者仅针对 Catch2，将变量 FETCHCONTENT_UPDATES_DISCONNECTED_Catch2 设置为 ON 。