I'm a newcomer in the world of CMake and Qt.

I want to create a small Qt application which can count factorial of any number. To do this in C , I use boost library.

Generally, when I write C code with boost, I compile it in this way -

g   MyCode.cpp -I "C:\boost" -o MyCode.exe

Now I'm trying to do the same in Qt. Here is the code of CMakeLists.txt :-

cmake_minimum_required(VERSION 3.14)

project(FirstProject-ConsoleApplication LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(Boost_USE_STATIC_LIBS ON)
set(Boost_USE_MULTITHREADED ON)
set(Boost_USE_STATIC_RUNTIME ON)
# find_package(Boost 1.76.0 COMPONENTS ...)

if(Boost_FOUND)
    include_directories(${Boost_INCLUDE_DIRS})
    add_executable(progname file1.cxx file2.cxx)
    target_link_libraries(progname ${Boost_LIBRARIES})
endif()

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core)

add_executable(FirstProject-ConsoleApplication
  main.cpp
)
target_link_libraries(FirstProject-ConsoleApplication Qt${QT_VERSION_MAJOR}::Core)

install(TARGETS FirstProject-ConsoleApplication
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

And this is the code for main.cpp file [This is a console application] :-

#include <QCoreApplication>
#include <QDebug>

#include <bits/stdc  .h>
#include <boost/multiprecision/cpp_int.hpp>  // 'boost/multiprecision/cpp_int.hpp' file not found

using namespace std;
using boost::multiprecision::cpp_int;  // Use of undeclared identifier 'boost'


cpp_int Factorial(int number) // Unknown type name 'cpp_int'
{
    cpp_int num = 1;
    for (int i = 1; i <= number; i  )
        num = num * i;
    return num;
}


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    std::cout << Factorial(50) << "\n";
    qInfo() << Factorial(100) << "\n";

    return a.exec();
}

I want to know, how can I pass the directory of my boost folder to this CMakeLists.txt file so that the program gets built smoothly?

CodePudding user response：

According to the documentation for FindBoost, you can hint the location of Boost by setting the variable BOOST_ROOT. For example, assuming you run cmake from the path where CMakeList.txt is locate, you run

cmake -DBOOST_ROOT=/path/to/boost .

(The final "." indicate that CMakeList.txt is to be found in the current directory)

Or, you can indicate the location of the libraries and headers with the variables BOOST_LIBRARYDIR and BOOST_INCLUDEDIR

cmake -DBOOST_INCLUDEDIR=/path/to/boost/include -DBOOST_LIBRARYDIR=/path/to/boost/lib .

Alternatively, you could set these variables directly inside the CMakeList.txt file, adding before find_package

SET(BOOST_ROOT "/path/to/boost/")

or

SET(BOOST_INCLUDEDIR "/path/to/boost/include")
SET(BOOST_LIBRARYDIR "/path/to/boost/lib")

A couple of side remarks:

• #include <bits/stdc .h> should be avoided.
• using namespace std is condidered bad practice.