CMake中while/continue/break的使用

Posted 2022-12-10 fengbingchun

      CMake中的while命令用于在条件为true时评估(evaluate)一组命令，其格式如下：

while(<condition>)
  <commands>
endwhile()

      在while和匹配的endwhile之间的所有命令都被记录下来而不被调用。一旦评估了endwhile，只要<condition>为true,就会调用记录的命令列表。
      while中的<condition>与if命令中的<condition>具有相同语法和相同的逻辑进行评估。
      命令break和continue提供了从正常控制流中退出的方法。

set(var 1)
while($var LESS 4)
    message("var: $var")
    math(EXPR var "$var+1")
endwhile()

      CMake中的continue命令用于continue到foreach或while循环的顶部(top)，其格式如下：

continue()

      continue命令允许cmake脚本中止foreach或while循环的当前迭代的其余部分，并从下一次迭代的顶部开始。

set(var 1)
while($var LESS 4)
    message("var: $var")
    math(EXPR var "$var+1")
    if($var EQUAL 3)
        continue()
    endif()
    message("after math, var: $var")
endwhile()

      CMake中的break命令用于从foreach或while循环中中断(break)，其格式如下：从当前的foreach或while循环中退出

break()

set(var 1)
while($var LESS 4)
    message("var: $var")
    math(EXPR var "$var+1")
    if($var EQUAL 3)
        break()
    endif()
    message("after math, var: $var")
endwhile()
message("var: $var")

      执行上述测试代码需要3个文件：build.sh, CMakeLists.txt, test_while.cmake

      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)

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

      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_while.cmake:为上面的所有示例代码

      可能的执行结果如下图所示:

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