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I am totally new to cmake and its syntax .But fortunately I am able to run the cmake tutorial step 1 as per the introductions mention on below links :

https://cmake.org/cmake/help/latest/guide/tutorial/index.html

But I am totally stucked at step 2 project to run using cmake.

I have created the step 2 project and understand the syntax to link the library for doing square root of a number, But I did not understand how to run this as I am getting below error : 

user@server:~/TER_CMAKE/Tutorial/step2_build$ cmake ../step2
CMake Error at CMakeLists.txt:19 (add_subdirectory):
  The binary directory

    /home/user/TER_CMAKE/Tutorial/step2/MathFunctions

  is already used to build a source directory.  It cannot be used to build
  source directory

    /home/user/TER_CMAKE/Tutorial/step2/MathFunctions

  Specify a unique binary directory name.


-- Configuring incomplete, errors occurred!

The example is available at below location for step 2 under heading Adding a Library (Step 2)..

https://moodle.rrze.uni-erlangen.de/pluginfile.php/14829/mod_resource/content/5/CMakeTutorial.pdf

My intention is to run my example this way 

 step2_build$ cmake ../step2
 step2_build$ cmake --build .
 step2_build$ ./Tutorial 121

As I am not sure that is it good to ask this way on this platform ,But as I do not have any other guidance .I am doing this by my own .

Note: I do not wants to use any tool to run my step 2 example.I wants to run everything using command prompt and cmake command only .where I can understand the cmake .

Edit:

Adding my CMakeLists.txt = 

cmake_minimum_required(VERSION 3.5)

#set the project name
project(Tutorial VERSION 1.0)

#specify the c++ std
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED True)

option(USE_MYMATH "Use tutorial provided math implementation" ON)

#Configure a header file to pass the version number to the source code
configure_file(TutorialConfig.h.in TutorialConfig.h)

#add the MathFunctions Library
add_subdirectory(MathFunctions)

if(USE_MYMATH)
    add_subdirectory(MathFunctions)
    list(APPEND EXTRA_LIBS MathFunctions)
    list(APPEND EXTRA_INCLUDES "${PROJECT_SOURCE_DIR}/MathFunctions")
endif()


#add the executable
add_executable(Tutorial tutorial.cpp)

target_link_libraries(Tutorial PUBLIC ${EXTRA_LIBS})

# add the binary tree to the search path for include files
# so that we will find TutorialConfig.h
target_include_directories(Tutorial PUBLIC 
                           "${PROJECT_BINARY_DIR}"  
                           ${EXTRA_LIBS}
                          )

My Source tutorial.cpp file:

#include <iostream>
#include <cmath>
#include <cstdlib>
#include <string>

#ifdef USE_MYMATH
#include "MathFunctions.h"
#endif
#include "TutorialConfig.h"

using namespace std;

int main(int argc, char* argv[])
{
  if (argc < 2) {
    cout << "Usage: " << argv[0] << " number" << endl;
    return 1;
  }

  // convert input to double
  const double inputValue = atof(argv[1]);

  // calculate square root
#ifdef USE_MYMATH
  const double outputValue = mysqrt(inputValue);
#else
  const double outputValue = sqrt(inputValue);
#endif
  cout << "The square root of " << inputValue << " is " << outputValue << endl;
  return 0;
}

ToturialConfig.h.in file :

#define Tutorial_VERSION_MAJOR @Tutorial_VERSION_MAJOR@
#define Tutorial_VERSION_MINOR @Tutorial_VERSION_MINOR@

#cmakedefine USE_MYMATH

EDIT: Step2 has a folder MathFuctions,Which has Cmake file mysqrt.cpp file

/TER_CMAKE/Tutorial/step2/MathFunctions/CMakeLists.txt 

add_library(MathFunctions mysqrt.cpp)

/TER_CMAKE/Tutorial/step2/MathFunctions/mysqrt.cpp 

#include <iostream>

// a hack square root calculation using simple operations
double mysqrt(double x)
{
  if (x <= 0) {
    return 0;
  }

  double result = x;

  // do ten iterations
  for (int i = 0; i < 10; ++i) {
    if (result <= 0) {
      result = 0.1;
    }
    double delta = x - (result * result);
    result = result + 0.5 * delta / result;
    std::cout << "Computing sqrt of " << x << " to be " << result << std::endl;
  }
  return result;
}
mahesh narlekar
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  • I am totally new to this cmake .So asking in this manner.May be I am not following proper professionalism .But wants someones guidance to run this step2 example . – mahesh narlekar Jan 13 '20 at 12:22
  • The tutorial you refers to contains many **snippets**, some of which won't work together. Show **your code** (`CMakeLists.txt`) which you are trying to build. – Tsyvarev Jan 13 '20 at 12:32
  • @Tsyvarev,I have updated my post with my cmake list information . – mahesh narlekar Jan 13 '20 at 13:35

3 Answers3

1

In case USE_MYMATH variable is set add_subdirectory(MathFunctions) is invoked twice. You need to decide and remove one of the occurrences on lines 16 and 19 in you CMakeLists.txt.

Vladimir Berlev
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  • I have commented out line 16 .But How can I run my code.I have created step2_build folder outside step2 folder .And trying to run the code using : 1) step2_build$ cmake ../step2 (2) step2_build$ cmake --build . (3) step2_build$ ./Tutorial 121 ...But I am not able to get the ./Tutorial Executable ??I have updated my post with MATHFUNCTION cmake file and cpp file – mahesh narlekar Jan 14 '20 at 10:38
  • Actually if all the steps you mention complete successfully it must be there. Try to search for the file in your build directory: `step2_build$ find . -name Tutorial` – Vladimir Berlev Jan 14 '20 at 12:41
  • When I am trying to run below command,I am getting this error . => /TER_CMAKE/Tutorial/step2_build$ cmake --build . make: *** No targets specified and no makefile found. Stop. – mahesh narlekar Jan 14 '20 at 14:02
  • Only this runs . /TER_CMAKE/Tutorial/step2_build$ cmake ../step2 -- Configuring done -- Generating done -- Build files have been written to: /home/user/TER_CMAKE/Tutorial/step2 – mahesh narlekar Jan 14 '20 at 14:03
  • Should I run it from other folder location to generate the ./Tutorial executable ?? – mahesh narlekar Jan 14 '20 at 14:05
  • According to your comment, you have generated build tree to `/home/user/TER_CMAKE/Tutorial/step2`, so you have to run further commands in this directory. – Vladimir Berlev Jan 14 '20 at 14:46
  • I am able to run the first step : `. /TER_CMAKE/Tutorial/step2_build$ cmake ../step2 ` .But after that If I am trying to run the next command I Am getting error which is : ` /TER_CMAKE/Tutorial/step2_build$ cmake --build .` make: *** No targets specified and no makefile found. Stop. – mahesh narlekar Jan 15 '20 at 09:41
  • I got the issue .Your reply work well .Only I need to delete old cache and generated cmake folder from my old build .By mistake I have created that files at wrong location . – mahesh narlekar Jan 22 '20 at 14:03
  • Yes, sometimes you have to clean caches to make changes effective. – Vladimir Berlev Jan 23 '20 at 15:49
0

Two issues I can see:

  1. You're adding the subdirectory "MathFunctions" twice when you configure the build with -DUSE_MYMATH=ON. This is why you are getting "CMake Error at CMakeLists.txt:19 (add_subdirectory):"

To fix, remove

#add the MathFunctions Library
add_subdirectory(MathFunctions)

and rely on

if(USE_MYMATH)
    add_subdirectory(MathFunctions)
    list(APPEND EXTRA_LIBS MathFunctions)
    list(APPEND EXTRA_INCLUDES "${PROJECT_SOURCE_DIR}/MathFunctions")
endif()
  1. In your CMakeLists.txt file, you are doing
target_include_directories(Tutorial PUBLIC 
                           "${PROJECT_BINARY_DIR}"  
                           ${EXTRA_LIBS}
                          )

Instead of

${EXTRA_LIBS}

It should be

${EXTRA_INCLUDES}
marshallb
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in Discourse Cmake Org -- help with tutorial step 2

Josef Angstenberger jtxa said

The files in Step3 are the expected result if you do everything from Step2. Can you please compare your files against the ones from Step3 to see if there are any relevant differences?

Blockquote

Marshallb's solution will solve nahesh relkar's problem

Loading Step2/CMakeLists.txt and Step3/CMakeLists.txt into vimdiff helped me to fix mine

Thomas Bodine
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