Makefile: Undefined symbols for architecture x86_64

Question

I'm making my app more portable to run on other OS's. Works in XCode and Visual Studio. However, switching to Makefiles is causing me some problems.

Error:

Undefined symbols for architecture x86_64:                                     
"AppObject::Instance()", referenced from:                        
  _main in main-329f6c.o                                                                                          
ld: symbol(s) not found for architecture x86_64

Main.cpp

#include <iostream>

#include "AppObject.hpp"

AppObject* _appObject;

int main()
{
    _appObject = AppObject::Instance();

    return 0;
}

AppObject.hpp

#ifndef  _APPOBJECT_HPP_
#define  _APPOBJECT_HPP_

#include <iostream>

class AppObject
{
    public:
        static AppObject* Instance();
        virtual ~AppObject() {}

        void initInstance();

    private:
        AppObject();
        AppObject(const AppObject&);
        AppObject& operator= (const AppObject&);
        static AppObject* pinstance; 
};

#endif // _APPOBJECT_HPP_

AppObject.cpp

#include "AppObject.hpp"

AppObject* AppObject::pinstance = 0;

AppObject::AppObject() {}

AppObject* AppObject::Instance()
{
    if (pinstance == 0)
    {
        pinstance = new AppObject;
        pinstance->initInstance();
    }

    return pinstance;
}

void AppObject::initInstance()
{
   .....
}

This is paired down a bit but I am seeing some other warnings also of:

warning: in-class initialization of non-static data member is a C++11 extension

Can anyone help me understand my mistake and my this works in XCode and VS but not using make?

Makefile

CXX=clang++
CXXFLAGS=-g -std=c++11 -Wall -pedantic -c

LDFLAGS=-L/usr/local/opt/sqlite/lib
CPPFLAGS=-I/usr/local/opt/sqlite/include

SOURCES=scraper/main.cpp scraper/AppObject.cpp scraper/SQLManager.cpp

OBJECTS=$(SOURCES:.cpp=.o)

EXECUTABLE=scraper

all: $(SOURCES) $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS) 
    $(CXX) $(LDFLAGS) $(OBJECTS) -o $@

.cpp.o:
    $(CXX) $(CXXFLAGS) $< -o $@

Full make output:

$ make
clang  scraper/main.cpp -o scraper/main.o
In file included from scraper/main.cpp:3:
In file included from scraper/AppObject.hpp:6:
scraper/SQLManager.hpp:44:30: warning: in-class initialization of non-    static data member is a C++11 extension
  [-Wc++11-extensions]
        bool _bDatabaseReady = false;
                         ^
scraper/SQLManager.hpp:46:29: warning: in-class initialization of non-    static data member is a C++11 extension
  [-Wc++11-extensions]
        std::string _dbFile = "popcorn.db3";
                        ^
scraper/SQLManager.hpp:47:29: warning: in-class initialization of non-    static data member is a C++11 extension
  [-Wc++11-extensions]
        std::string _dbName = "popcorn";
                        ^
scraper/SQLManager.hpp:49:24: warning: in-class initialization of non-    static data member is a C++11 extension
      [-Wc++11-extensions]
        int _dbVersion = 1; // increment this when database structure changes
                   ^
scraper/SQLManager.hpp:51:28: warning: in-class initialization of non-static data member is a C++11 extension
      [-Wc++11-extensions]
        int _dbVersionType = 0; // 0 = normal, 1 = free, 2 = lite
                       ^
5 warnings generated.
Undefined symbols for architecture x86_64:
  "AppObject::Instance()", referenced from:
      _main in main-4a5276.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see     invocation)
make: *** [scraper/main.o] Error 1

Updated make output after taking advice from replies:

$ make
clang++  scraper/main.cpp -o scraper/main.o
In file included from scraper/main.cpp:3:
In file included from scraper/AppObject.hpp:6:
scraper/SQLManager.hpp:44:30: warning: in-class initialization of non-    static data member is a C++11 extension [-Wc++11-extensions]
        bool _bDatabaseReady = false;
                         ^
scraper/SQLManager.hpp:46:29: warning: in-class initialization of non-    static data member is a C++11 extension [-Wc++11-extensions]
        std::string _dbFile = "popcorn.db3";
                        ^
scraper/SQLManager.hpp:47:29: warning: in-class initialization of non-    static data member is a C++11 extension [-Wc++11-extensions]
        std::string _dbName = "popcorn";
                        ^
scraper/SQLManager.hpp:49:24: warning: in-class initialization of non-    static data member is a C++11 extension [-Wc++11-extensions]
        int _dbVersion = 1; // increment this when database structure changes
                   ^
scraper/SQLManager.hpp:51:28: warning: in-class initialization of non-    static data member is a C++11 extension [-Wc++11-extensions]
        int _dbVersionType = 0; // 0 = normal, 1 = free, 2 = lite
                       ^
5 warnings generated.
Undefined symbols for architecture x86_64:
  "AppObject::Instance()", referenced from:
      _main in main-0e97bb.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see     invocation)
make: *** [scraper/main.o] Error 1

And totally unrelated to your problem, but still relevant: [What are the rules about using an underscore in a C++ identifier?](http://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier) — Some programmer dude, Aug 15 '18 at 13:24
And please copy-paste the full output of your run with `make`. Delete all object, executable and other temporary files, and run a clean `make`. — Some programmer dude, Aug 15 '18 at 13:26
Use `$(CXX)` to build and link C++ sources, `$(CC)` is for C. — Maxim Egorushkin, Aug 15 '18 at 13:26
@MaximEgorushkin I switched to `$(CXX)` and the errors persist. — Jasmine, Aug 15 '18 at 13:32
@Jason It will be a lot easier to see where the error is if you show us all the commands being run (that is, delete all object and exe files, run make and copy paste the output) — nos, Aug 15 '18 at 13:40
@nos post updated with full output. Some classes referenced I omitted from this post. — Jasmine, Aug 15 '18 at 14:00

score 0 · Answer 1 · answered Aug 15 '18 at 14:04

0

To begin with, clang is the C frontend. While it can be used to compile C++ code, it will not add all header paths or linker libraries needed for C++. Use clang++.

Secondly, the output you show is without any flags at all.

Thirdly, and the reason for your linker error, is that you don't use the -c flag which is needed to create object files. Without the -c flag, you tell the clang frontend program to build and link an executable file named scraper/main.o.

answered Aug 15 '18 at 14:04

Some programmer dude

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I fixed those and still the same errors. I updated the Makefile above to reflect – Jasmine Aug 15 '18 at 19:35
@Jason But you forgot to update the output you get from building. And if you get the exact same output, then you're not editing with the `Makefile` you're using to build. – Some programmer dude Aug 15 '18 at 20:02
hmm, I am editing the makefile I am using (doing so from a command-line). I am getting the same output, but I'll update to show it is now using `clang++` and `-c`. – Jasmine Aug 15 '18 at 21:29

Makefile: Undefined symbols for architecture x86_64

1 Answers1