第二节

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Step 2:adding a library

Exercise 1 - creating a library

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add_library(MathFunctions MathFunctions.cxx mysqrt.cxx)

add_subdirectory(MathFunctions)

target_link_libraries(Tutorial PUBLIC MathFunctions)

target_include_directories(Tutorial PUBLIC 
                        "${PROJECT_BINARY_DIR}" 
                        "${PROJECT_SOURCE_DIR}/MathFunctions"
                        )

Exercise 2 - adding an option

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# MathFunctions/CMakeLists.txt
option(USE_MYMATH "Use tutorialc provided math implementation" ON)

if(USE_MYMATH)
    target_compile_definitions(MathFunctions PRIVATE "USE_MYmATH")
    add_library(SqrtLibrary STATIC
            mysqrt.cxx
            )
    target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
endif()

add_library(MathFunction MathFunctions.cxx)
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# MathFunctions/MathFunctions.cxx

#ifdef USE_MYMATH
    return detail::mysqrt(x);
#else
    return std::sqrt(x);
#endif

#ifdef USE_MYMATH
#   include "mysqrt.h"
#endif

#include  <cmath>