（5）CMake入门笔记--CMake官网教程

蔚落 2021-11-02 11:18 350阅读 0赞

# 五．添加生成的文件和生成器 #

在本节中，我们将展示如何将生成的源文件添加到应用程序的构建过程中。 对于此示例，我们将创建一个预先计算的平方根表，作为构建过程的一部分，然后将该表编译到我们的应用程序中。 为此，我们首先需要一个生成表的程序。 在MathFunctions子目录中，一个名为MakeTable.cxx的新源文件就是这样做的。

// A simple program that builds a sqrt table
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    
    int main (int argc, char *argv[])
    {
      int i;
      double result;
    
      // make sure we have enough arguments
      if (argc < 2)
      {
        return 1;
      }
    
      // open the output file
      FILE *fout = fopen(argv[1],"w");
      if (!fout)
      {
        return 1;
      }
    
      // create a source file with a table of square roots
      fprintf(fout,"double sqrtTable[] = {\n");
      for (i = 0; i < 10; ++i)
      {
        result = sqrt(static_cast<double>(i));
        fprintf(fout,"%g,\n",result);
      }
    
      // close the table with a zero
      fprintf(fout,"0};\n");
      fclose(fout);
      return 0;
    }

请注意，该表是作为有效的C ++代码生成的，并且将输出的文件的名称作为参数传入。 下一步是将适当的命令添加到MathFunctions的CMakeLists.txt文件以构建MakeTable可执行文件，然后在构建过程中运行它。 完成此操作需要一些命令，如下所示。

# first we add the executable that generates the table
    add_executable(MakeTable MakeTable.cxx)
    
    # add the command to generate the source code
    add_custom_command (
      OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/Table.h
      COMMAND MakeTable ${CMAKE_CURRENT_BINARY_DIR}/Table.h
      DEPENDS MakeTable
      )
    
    # add the binary tree directory to the search path for
    # include files
    include_directories( ${CMAKE_CURRENT_BINARY_DIR} )
    
    # add the main library
    add_library(MathFunctions mysqrt.cxx ${CMAKE_CURRENT_BINARY_DIR}/Table.h  )

首先添加MakeTable的可执行文件。 然后我们添加一个自定义命令，指定如何通过运行MakeTable来生成Table.h。 接下来我们要让CMake知道mysqrt.cxx依赖于生成的文件Table.h。 这是通过将生成的Table.h添加到库MathFunctions的源列表中完成的。 我们还必须将当前二进制目录添加到包含目录列表中，以便可以在mysqrt.cxx中找到并包含Table.h。 构建此项目时，它将首先构建MakeTable可执行文件（DEPENDS MakeTable的作用，如果可执行已有则可以没有这句话）。 然后它将运行MakeTable以生成Table.h。 最后，它将编译包含Table.h的mysqrt.cxx以生成MathFunctions库。 此时，顶级CMakeLists.txt文件包含我们添加的所有功能，如下所示：

cmake_minimum_required (VERSION 2.6)
    project (Tutorial)
    include(CTest)
    
    # The version number.
    set (Tutorial_VERSION_MAJOR 1)
    set (Tutorial_VERSION_MINOR 0)
    
    # does this system provide the log and exp functions?
    include (${CMAKE_ROOT}/Modules/CheckFunctionExists.cmake)
    
    check_function_exists (log HAVE_LOG)
    check_function_exists (exp HAVE_EXP)
    
    # should we use our own math functions
    option(USE_MYMATH
      "Use tutorial provided math implementation" ON)
    
    # configure a header file to pass some of the CMake settings
    # to the source code
    configure_file (
      "${PROJECT_SOURCE_DIR}/TutorialConfig.h.in"
      "${PROJECT_BINARY_DIR}/TutorialConfig.h"
      )
    
    # add the binary tree to the search path for include files
    # so that we will find TutorialConfig.h
    include_directories ("${PROJECT_BINARY_DIR}")
    
    # add the MathFunctions library?
    if (USE_MYMATH)
      include_directories ("${PROJECT_SOURCE_DIR}/MathFunctions")
      add_subdirectory (MathFunctions)
      set (EXTRA_LIBS ${EXTRA_LIBS} MathFunctions)
    endif (USE_MYMATH)
    
    # add the executable
    add_executable (Tutorial tutorial.cxx)
    target_link_libraries (Tutorial  ${EXTRA_LIBS})
    
    # add the install targets
    install (TARGETS Tutorial DESTINATION bin)
    install (FILES "${PROJECT_BINARY_DIR}/TutorialConfig.h"       
             DESTINATION include)
    
    # does the application run
    add_test (TutorialRuns Tutorial 25)
    
    # does the usage message work?
    add_test (TutorialUsage Tutorial)
    set_tests_properties (TutorialUsage
      PROPERTIES
      PASS_REGULAR_EXPRESSION "Usage:.*number"
      )
    
    #define a macro to simplify adding tests
    macro (do_test arg result)
      add_test (TutorialComp${arg} Tutorial ${arg})
      set_tests_properties (TutorialComp${arg}
        PROPERTIES PASS_REGULAR_EXPRESSION ${result}
        )
    endmacro (do_test)
    
    # do a bunch of result based tests
    do_test (4 "4 is 2")
    do_test (9 "9 is 3")
    do_test (5 "5 is 2.236")
    do_test (7 "7 is 2.645")
    do_test (25 "25 is 5")
    do_test (-25 "-25 is 0")
    do_test (0.0001 "0.0001 is 0.01")
    TutorialConfig.h.in如下：
    // the configured options and settings for Tutorial
    #define Tutorial_VERSION_MAJOR @Tutorial_VERSION_MAJOR@
    #define Tutorial_VERSION_MINOR @Tutorial_VERSION_MINOR@
    #cmakedefine USE_MYMATH
    
    // does the platform provide exp and log functions?
    #cmakedefine HAVE_LOG
    #cmakedefine HAVE_EXP

MathFunctions的CMakeLists.txt文件如下所示：

# first we add the executable that generates the table
    add_executable(MakeTable MakeTable.cxx)
    # add the command to generate the source code
    add_custom_command (
      OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/Table.h
      DEPENDS MakeTable
      COMMAND MakeTable ${CMAKE_CURRENT_BINARY_DIR}/Table.h
      )
    # add the binary tree directory to the search path
    # for include files
    include_directories( ${CMAKE_CURRENT_BINARY_DIR} )
    
    # add the main library
    add_library(MathFunctions mysqrt.cxx ${CMAKE_CURRENT_BINARY_DIR}/Table.h)
    
    install (TARGETS MathFunctions DESTINATION bin)
    install (FILES MathFunctions.h DESTINATION include)