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Use Fetchcontent instead of ExternalProject #3314

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63 changes: 12 additions & 51 deletions googletest/README.md
Original file line number Diff line number Diff line change
Expand Up @@ -85,69 +85,30 @@ main build can be done a few different ways:
is just a little more complex, but doesn't have the limitations of the other
methods.

The last of the above methods is implemented with a small piece of CMake code in
a separate file (e.g. `CMakeLists.txt.in`) which is copied to the build area and
then invoked as a sub-build _during the CMake stage_. That directory is then
pulled into the main build with `add_subdirectory()`. For example:
The last of the above methods is implemented with a small piece of CMake so the
code is pulled into the main build.

New file `CMakeLists.txt.in`:
Just add to your `CMakeLists.txt`:

```cmake
cmake_minimum_required(VERSION 2.8.12)

project(googletest-download NONE)

include(ExternalProject)
ExternalProject_Add(googletest
GIT_REPOSITORY https://github.com/google/googletest.git
GIT_TAG master
SOURCE_DIR "${CMAKE_CURRENT_BINARY_DIR}/googletest-src"
BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/googletest-build"
CONFIGURE_COMMAND ""
BUILD_COMMAND ""
INSTALL_COMMAND ""
TEST_COMMAND ""
include (FetchContent)
FetchContent_Declare(
googletest
# Specify the commit you depend on and update it regularly.
URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
)
```

Existing build's `CMakeLists.txt`:

```cmake
# Download and unpack googletest at configure time
configure_file(CMakeLists.txt.in googletest-download/CMakeLists.txt)
execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
RESULT_VARIABLE result
WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
if(result)
message(FATAL_ERROR "CMake step for googletest failed: ${result}")
endif()
execute_process(COMMAND ${CMAKE_COMMAND} --build .
RESULT_VARIABLE result
WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
if(result)
message(FATAL_ERROR "Build step for googletest failed: ${result}")
endif()

# Prevent overriding the parent project's compiler/linker
# settings on Windows
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)

# Add googletest directly to our build. This defines
# the gtest and gtest_main targets.
add_subdirectory(${CMAKE_CURRENT_BINARY_DIR}/googletest-src
${CMAKE_CURRENT_BINARY_DIR}/googletest-build
EXCLUDE_FROM_ALL)
FetchContent_MakeAvailable(googletest)

# Now simply link against gtest or gtest_main as needed. Eg
add_executable(example example.cpp)
target_link_libraries(example gtest_main)
add_test(NAME example_test COMMAND example)
```

Note that this approach requires CMake 2.8.2 or later due to its use of the
`ExternalProject_Add()` command. The above technique is discussed in more detail
in [this separate article](http://crascit.com/2015/07/25/cmake-gtest/) which
also contains a link to a fully generalized implementation of the technique.
Note that this approach requires CMake 3.14 or later due to its use of the
`FetchContent_MakeAvailable()` command.

##### Visual Studio Dynamic vs Static Runtimes

Expand Down