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• 目录结构.

• .
  ├── CMakeLists.txt
  ├── include
  │   └── config.h.in
  ├── main.cc
  └── mymath
      ├── CMakeLists.txt
      ├── include
      │   └── mymath.h.in
      └── mysqrt.cc 

•  1 # @file   CMakeLists.txt
   2 # @brief  top level cmake file
   3 # @author loop0day
   4 # @date   2018-4-25
   5 
   6 # minimum version
   7 cmake_minimum_required(VERSION 3.0)
   8 
   9 # project name
  10 project(
  11   mylibrary
  12   VERSION 1.0
  13 )
  14 
  15 # configured header files
  16 configure_file (
  17   "${PROJECT_SOURCE_DIR}/include/config.h.in"
  18   "${PROJECT_BINARY_DIR}/include/config.h"
  19 )
  20 
  21 # add binary path to search header files
  22 include_directories(${PROJECT_BINARY_DIR}/include)
  23 
  24 # additional option
  25 option(USE_MYMATH "use mymath lib" OFF)
  26 
  27 # use mymath lib
  28 if(USE_MYMATH)
  29   # add mymath headers
  30   include_directories(${PROJECT_BINARY_DIR}/mymath/include)
  31   # add a sub lib path
  32   add_subdirectory(mymath)
  33   # add mymath lib  
  34   set(LIBS mymath)
  35 endif(USE_MYMATH)
  36 
  37 # add a executable target
  38 add_executable(proc main.cc)
  39 
  40 # link extra library
  41 target_link_libraries(proc ${LIBS}) 

•  1 /**
   2  * @file    config.h
   3  * @brief   process cmake config header
   4  * @author  loop0day
   5  * @date    2018-4-25
   6  */
   7 
   8 #ifndef CONFIG_H_
   9 #define CONFIG_H_
  10 
  11 /* version */
  12 #define PROJECT_VERSION_MAJOR @PROJECT_VERSION_MAJOR@
  13 #define PROJECT_VERSION_MINOR @PROJECT_VERSION_MINOR@
  14 
  15 #cmakedefine USE_MYMATH
  16 
  17 #endif /* ifndef CONFIG_H_ */

•  1 /**
   2  * @file    main.cc
   3  * @brief   process entry point
   4  * @author  loop0day
   5  * @date    2018-4-25
   6  */
   7 
   8 #include <cstdio>
   9 #include <cstdint>
  10 #include <config.h>
  11 
  12 #if defined(USE_MYMATH)
  13 #include <mymath.h>
  14 #else
  15 #include <cmath>
  16 #endif /* USE_MYMATH */
  17 
  18 int main(int , char * argv[])
  19 {
  20   uint32_t num, result;
  21 
  22   printf("%s version %d.%d\n", argv[0], PROJECT_VERSION_MAJOR, PROJECT_VERSION_MINOR);
  23 
  24   puts("Please input a num: ");
  25   scanf("%u", &num); 
  26 
  27 
  28 #if defined(USE_MYMATH)
  29   result = static_cast<num_t>(mysqrt(static_cast<num_t>(num)));
  30 #else
  31   result = static_cast<uint32_t>(sqrt(static_cast<double>(num)));
  32 #endif /* USE_MYMATH */
  33 
  34   printf("The square root of %u is %u\n", num, result);
  35 
  36   return 0;
  37 } 

•  1 # @file   CMakeLists.txt
   2 # @brief  mymath lib cmake file
   3 # @author loop0day
   4 # @date   2018-4-25
   5 
   6 # minimum version
   7 cmake_minimum_required(VERSION 3.0)
   8 
   9 # version
  10 set(MYMATH_VERSION_MAJOR 1)
  11 set(MYMATH_VERSION_MINOR 0)
  12 
  13 # add configured header files
  14 configure_file(
  15   "${CMAKE_CURRENT_SOURCE_DIR}/include/mymath.h.in"
  16   "${CMAKE_CURRENT_BINARY_DIR}/include/mymath.h"
  17 )
  18 
  19 # add include dir
  20 include_directories(${CMAKE_CURRENT_BINARY_DIR}/include)
  21 
  22 # add a library
  23 add_library(mymath mysqrt.cc) 

•  1 /**
   2  * @file    mymath.h
   3  * @brief   mymath lib cmake config header
   4  * @author  loop0day
   5  * @date    2018-4-25
   6  */
   7 
   8 #ifndef MYMATH_H_
   9 #define MYMATH_H_
  10 
  11 /* mymath lib version */
  12 #define MYMATH_VERSION_MAJOR @MYMATH_VERSION_MAJOR@
  13 #define MYMATH_VERSION_MINOR @MYMATH_VERSION_MINOR@
  14 
  15 #include <cstdio>
  16 
  17 typedef unsigned int num_t;
  18 
  19 /**
  20  * @brief   my custom func computes the square root of a number
  21  * @param   num the number
  22  * @return  the square root of the num
  23  */
  24 num_t mysqrt(const num_t & num);
  25 
  26 #endif /* ifndef MYMATH_H_ */ 

•  1 /**
   2  * @file    mysqrt.h
   3  * @brief   my simple sqrt imp
   4  * @author  loop0day
   5  * @date    2018-4-25
   6  */
   7 
   8 #include <mymath.h>
   9 
  10 num_t mysqrt(const num_t & num)
  11 {
  12   /* print version */
  13   printf("mymath version %d.%d\n", MYMATH_VERSION_MAJOR, MYMATH_VERSION_MINOR);
  14 
  15   num_t i;
  16   for (i = 1; i * i <= num; i++) ;
  17 
  18   return i - 1;
  19 }

• 看代码吧, 代码比我说的好.