CMake中aux_source_directory的使用

      CMake中的aux_source_directory命令用于查找目录中的所有源文件，其格式如下：

aux_source_directory(<dir> <variable>)

      收集指定目录中所有源文件的名称，并将列表(list)存储在提供的<variable>中。该命令旨在由使用显式模板实例化(explicit template instantiation)的项目使用。模板实例化文件可以存储在Templates子目录中，并使用此命令自动收集，以避免手动列出所有实例化。
      试图使用此命令来避免编写库或可执行target的源文件列表。尽管这似乎可行，但是CMake生成的构建系统无法知道何时添加新源文件到构建系统。通常，生成的构建系统知道何时需要重新运行CMake，因为CMakeLists.txt文件被修改为添加新源(new source)。当仅将源代码添加到目录而不修改该文件(CMakeLists.txt)时，将不得不手动重新运行CMake来生成包含新文件的构建系统。

aux_source_directory(source var)
message("var: ${var}") # var: source/add.cpp;source/multipy.cpp;source/subtraction.cpp

# 注意:下面的var会包含source和samples的文件,而不仅仅是只有samples中的
aux_source_directory(samples var)
message("var: ${var}") # var: source/add.cpp;source/multipy.cpp;source/subtraction.cpp;samples/sample_add.cpp;samples/sample_multipy.cpp;samples/sample_subtraction.cpp

# 注意:虽然include目录中不存在源文件,但是var的值并不为空,它保留了之前已存在的结果
aux_source_directory(include var)
message("var: ${var}") # var: source/add.cpp;source/multipy.cpp;source/subtraction.cpp;samples/sample_add.cpp;samples/sample_multipy.cpp;samples/sample_subtraction.cpp

unset(var)
aux_source_directory(samples var)
message("var: ${var}") # var: samples/sample_add.cpp;samples/sample_multipy.cpp;samples/sample_subtraction.cpp

      执行测试代码需要多个文件：

      build.sh内容如下：

#! /bin/bash

# supported input parameters(cmake commands)
params=(function macro cmake_parse_arguments \
		find_library find_path find_file find_program find_package \
		cmake_policy cmake_minimum_required project include \
		string list set foreach message option if while return \
		math file configure_file \
		include_directories add_executable add_library target_link_libraries install \
		target_sources add_custom_command add_custom_target \
		add_subdirectory aux_source_directory \
		set_property set_target_properties define_property)

usage()
{
	echo "Error: $0 needs to have an input parameter"

	echo "supported input parameters:"
	for param in ${params[@]}; do
		echo "  $0 ${param}"
	done

	exit -1
}

if [ $# != 1 ]; then
	usage
fi

flag=0
for param in ${params[@]}; do
	if [ $1 == ${param} ]; then
		flag=1
		break
	fi
done

if [ ${flag} == 0 ]; then
	echo "Error: parameter \"$1\" is not supported"
	usage
	exit -1
fi

if [[ ! -d "build" ]]; then
	mkdir build
	cd build
else
	cd build
fi

echo "==== test $1 ===="

# test_set.cmake: cmake -DTEST_CMAKE_FEATURE=$1 --log-level=verbose ..
# test_option.cmake: cmake -DTEST_CMAKE_FEATURE=$1 -DBUILD_PYTORCH=ON ..
cmake -DTEST_CMAKE_FEATURE=$1 ..
# It can be executed directly on the terminal, no need to execute build.sh, for example: cmake -P test_set.cmake
make
# make install # only used in cmake files with install command

      CMakeLists.txt内容如下：

cmake_minimum_required(VERSION 3.22)
project(cmake_feature_usage)

message("#### current cmake version: ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}.${CMAKE_PATCH_VERSION}")
include(test_${TEST_CMAKE_FEATURE}.cmake)
message("==== test finish ====")

      test_aux_source_directory.cmake内容为上面的所有测试代码段。

      另外还包括三个目录：include,source,samples,它们都是非常简单的实现，仅用于测试，如下：

      可能的执行结果如下图所示:

      GitHub： https://github.com/fengbingchun/Linux_Code_Test