I'm writing a simple game engine, and I have the EntityComponent.h file:
#ifndef Psycho2D_Core_EntityComponent_
#define Psycho2D_Core_EntityComponent_
#include <string>
namespace psycho2d{
class EntityComponent{
private:
std::string m_name;
public:
EntityComponent(const std::string &name);
virtual ~EntityComponent();
const std::string& getName() const;
virtual void initialize() = 0;
virtual void loadProperties() = 0;
virtual void update() = 0;
virtual void destroy() = 0;
};
}
#endif
And the relative EntityComponent.cpp file:
#include "EntityComponent.h"
#include <string>
psycho2d::EntityComponent::EntityComponent(const std::string &name){
this->m_name = name;
}
psycho2d::EntityComponent::~EntityComponent(){}
inline const std::string& psycho2d::EntityComponent::getName() const{
return this->m_name;
}
These two file are part of a framework (I'm working on a Mac). They compile well.
The problem is when I write an executable that use the library.
I have created a sub-class of EntityComponent, and it compiles. But, if I call the getName() function, the linker tell me:
"psycho2d::EntityComponent::getName() const", referenced from:
_main in main.o
Symbol(s) not found
Collect2: ld returned 1 exit status
What I can do?
Thanks.
Put the code for the inline function in the header file, if you want to reference it from multiple .cpp files.
Reference here.
An external linkage inline function must defined (as effectively the same) in every translation unit where it's used.
So either remove the inline from the definition, or place the definition in the header file.
Cheers & hth.,
Your (slightly modified to include a subclass to text) code compiles fine on my machine (A Mac, too. GCC 4.2.1)
Try removing all .o-files and compile with a clean directory. If that fails too, I'd try to remove the inline-definition.
Try removing the inline qualifier from your implementation.
Related
I have seen many related questions to this problem, but after carefully following advice from members, my problem still persists. The code is quite simple. I only have the following header file ("instrument.h"), which contains the base class and the template class:
#include <stdio.h>
#include <string>
using namespace std;
class Instrument
{
public:
Instrument();
virtual void print() const = 0;
};
template <class parameter> class Equity : public Instrument
{
public:
Equity();
virtual void print() const;
};
Now, in my main function on main.cpp I only do the following:
#include "instrument.h"
#include <iostream>
int main() {
Equity<double> pb;
return 0;
}
Well, I get the very well-known error:
Undefined symbols for architecture x86_64:
"Equity<double>::Equity()", referenced from:
_main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I have already changed in Build Settings the C++ standard library to libstdc++, also to default compiler, and so on. Do I have a problem with my project settings? Is perhaps the template wrongly implemented? I was thinking I should also have a instrument.cpp file, but then again definitions for templates must be kept in the header file so that would probably crash too.
Thanks in advance
You declared the default constructors for both Instrument and Equity but defined them nowhere.
Alter their definitions appropriately:
public:
Equity() = default; // Or {} in pre-C++11
// ^^^^^^^^^
(And equivalently for Instrument)
You can also completely omit the declarations of any default constructors for now since you didn't declare any other constructors in both Equity and Instrument and the default constructors will be generated automatically.
I'm following a Cocos2D-X tutorial for iOS on XCode 5 and the instructor started off by creating a bunch of classes and header files. Among those is a header file called "Utils.h" that contains some static functions
class Utils
{
public:
static Game* gameLayer();
static HUD* hudLayer();
static cocos2d::CCLayer* layerWithTag(int tag);
static cocos2d::CCSize s();
static cocos2d::CCAnimate* getAnimationWithFrames(int from, int to);
static void scaleSprite(cocos2d::CCSprite * sprite);
static float getScale();
static void setScale(float s);
static float getArtScaleFactor();
static void setArtScaleFactor(int s);
};
The s() functions is defined in Utils.cpp to just return CCDirector::sharedDirector()->getWinSize();
Now, the problem is: when the s() function is called in my main menu scene (Utils::s().width for instance), I get this error "Linker command failed with exit code 1 (use -v to see invocation)" and "Symbol(s) not found for architecture i386". However, when I deleted the s() function definition from Utils.cpp and just added the function in the class in the header file so that it becomes
//Utils.h
class Utils
{
public:
.......
static cocos2d::CCSize s()
{
return CCDirector::sharedDirector()->getWinSize();
}
......
It compiles without an error...
Why is it that I get this error when the function is in the cpp file instead of the header file? I know my problem is already solved but it's just driving me crazy
Thanks! :)
Edit: I thought this was a given but to be clearer, in the main menu scene I included Utils.h not Utils.cpp
Please note that such errors also appear when you have declared a function in one file (say Cpp) and not in the .h file.
Most common reason that i have seen is because one declares a function in the .h file but forget to give the implementation.
In a library, I have the following in a header:
// button.hpp
class ExtraButtons
{
public:
static inline void show() { setShown(true); }
static inline void hide() { setShown(false); }
static void setShown(bool shown);
};
and the following in a source file:
#include "button.hpp"
void ExtraButtons::setShown(bool shown)
{
}
The library compiles fine. However, when I'm using the library and I include button.hpp, I get this error from the setShown calls in show() and hide():
undefined reference to `ExtraButtons::setShown(bool)'
I can fix the problem by removing the inline from show() and hide() and defining them in the source file, like normal, OR by making setShown inline as well. Why is this the case? Are these the only solutions?
It looks like either you aren't linking the library binary into your project, or your actual definition for setShown is inline void ExtraButtons::setShown(bool shown) (note that it's accidentally marked inline in the source file).
I'm having a strange issue when compiling an open source library. When compiling for the device, Xcode compiles it just fine and deploys it no problem. However, when I compile for the simulator, I get duplicate symbol errors during the linking phase.
I've checked a few of these out, and it seems these symbols were all implemented in the .hh file as opposed to the .m file. Obviously this is bad code structure, and the errors make sense. However, what doesn't make sense is why there are no errors for the device build.
Each of these .hh files contains #pragma once at the top of the file. My initial thought was that this wasn't working as expected, but upon removal I get compile-time errors for both device and simulator builds stating I've redefined these symbols. Hmm, so I then tried replacing #pragma once with
#ifndef EXAMPLE_DEFINE
#define EXAMPLE_DEFINE
// code
#end if
But this yields identical results to the #pragma once.
Due to the sheer number of code changes that would be required, it isn't feasible for me to go through and fix every error manually, especially since I'll want to be able to update the codebase easily. So is there any reason this is not failing for the device, and how I could make simulator builds perform the same way?
EDIT: I've also tested using #import instead of #include, but it too yields the same results
EDIT 2: After more testing, I've found that if I define a Preprocessor macro in the target's build settings, the code inside the #ifndef never gets called, as is expected. For whatever reason, it looks like defining the new definition in the .hh file isn't being carried over into the next compilation of the file.
Also, as requested, here's an excerpt from the build log
duplicate symbol __ZZN12DelegateFuncIFvR16DualTextMenuItemRKN5Input5EventEEEC1IZN25MultiChoiceSelectMenuItem4initEPPKciiibSB_P12ResourceFaceEUlS1_S5_E_EERKT_PNSt3__19enable_ifIXntsr3std11is_functionISG_EE5valueEvE4typeEENKS8_ISF_EUlRKNS7_7StorageES1_S5_E_cvPFvSR_S1_S5_EEv in:
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/Main-FB93852047D42061.o
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/OptionView.o
duplicate symbol __ZZN12DelegateFuncIFbiRKN5Input5EventEEEC1IZN15MultiChoiceView4initER19MultiChoiceMenuItemb9_2DOriginEUliS3_E_EERKT_PNSt3__19enable_ifIXntsr3std11is_functionISC_EE5valueEvE4typeEENKS6_ISB_EUlRKNS5_7StorageEiS3_E_cvPFbSN_iS3_EEv in:
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/Main-FB93852047D42061.o
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/OptionView.o
duplicate symbol __ZZN12DelegateFuncIFvR12TextMenuItemRKN5Input5EventEEEC1IN14YesNoAlertView2noMUlS1_S5_E_EEERKT_PNSt3__19enable_ifIXntsr3std11is_functionISB_EE5valueEvE4typeEENKS8_ISA_EUlRKNS7_7StorageES1_S5_E_cvPFvSM_S1_S5_EEv in:
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/ButtonConfigView.o
/Users/riley.testut/Library/Developer/Xcode/DerivedData/GBA4iOS-dqkflotukruucqbxjyslhtfuekse/Build/Intermediates/GBA4iOS.build/Debug-iphonesimulator/GBA4iOS.build/Objects-normal/i386/MenuView.o
ld: 16 duplicate symbols for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
and here's one of the offending files (AlertView.hh):
#pragma once
#include <gui/View.hh>
#include <gui/MenuItem/MenuItem.hh>
#include <util/gui/BaseMenuView.hh>
#include <util/rectangle2.h>
#include <util/DelegateFunc.hh>
class AlertView : public View
{
public:
constexpr AlertView() { }
Rect2<GC> labelFrame;
Gfx::Text text;
BaseMenuView menu;
Rect2<int> rect;
Rect2<int> &viewRect() { return rect; }
void init(const char *label, MenuItem **menuItem, bool highlightFirst);
void deinit() override;
void place() override;
void inputEvent(const Input::Event &e) override;
void draw(Gfx::FrameTimeBase frameTime) override;
};
class YesNoAlertView : public AlertView
{
public:
YesNoAlertView() { }
typedef DelegateFunc<void (const Input::Event &e)> InputDelegate;
MenuItem *menuItem[2] = {nullptr};
// Optional delegates
InputDelegate &onYes() { return onYesD; }
InputDelegate &onNo() { return onNoD; }
void init(const char *label, bool highlightFirst, const char *choice1 = nullptr, const char *choice2 = nullptr)
{
yes.init(choice1 ? choice1 : "Yes"); menuItem[0] = &yes;
no.init(choice2 ? choice2 : "No"); menuItem[1] = &no;
assert(!onYesD);
assert(!onNoD);
AlertView::init(label, menuItem, highlightFirst);
}
void deinit() override
{
logMsg("deinit alert");
AlertView::deinit();
onYesD = {};
onNoD = {};
}
InputDelegate onYesD;
InputDelegate onNoD;
private:
TextMenuItem yes
{
[this](TextMenuItem &, const Input::Event &e)
{
auto callback = onYesD;
removeModalView();
if(callback) callback(e);
}
};
TextMenuItem no
{
[this](TextMenuItem &, const Input::Event &e)
{
auto callback = onNoD;
removeModalView();
if(callback) callback(e);
}
};
};
It shows you have tried the header guards but my suggestion is once you check for following
link.
http://en.wikipedia.org/wiki/Include_guard
http://c2.com/cgi/wiki?RedundantIncludeGuards
The update shows it is linker error for symbols and this is for the library you are using.
I've been searching for a while and have found a lot of threads/pages that involve the problem I have, but I am not able to find
An explanation of why this error occurs
A working solution for my specific case
The following is Scanner.h:
class BaseReader {
public:
virtual ~BaseReader();
virtual const char* read() = 0;
virtual long position() = 0;
virtual long size() = 0;
virtual void seek(long position) = 0;
};
class CharReader : public BaseReader {
public:
CharReader(const char* source);
CharReader(const char* source, long size);
~CharReader();
const char* read();
long position();
long size();
void seek(long position);
private:
char* _source;
long _position;
long _size;
};
In Scanner.cpp I simply implement one of the constructors of CharReader.
I use Code::Blocks, but compiling it by myself results in the exact same problem.
niklas#emerald:~/git/hiterator (CPP)$ g++ main.cpp hiterator/Scanner.cpp -o main
/tmp/cclNNwgl.o: In function `hiterator::CharReader::CharReader(char const*)':
Scanner.cpp:(.text+0x16): undefined reference to `vtable for hiterator::CharReader'
collect2: ld gab 1 als Ende-Status zurück
#qdii:
#include "Scanner.h"
using namespace hiterator;
#include <stdlib.h>
#include <string.h>
CharReader::CharReader(const char* source) {
_size = strlen(source);
_source = (char*) malloc(_size + 1);
memcpy(_source, source, _size + 1);
}
Your program is incorrect. All virtual functions are considered used (odr-used) and thus you need to provide the definitions for all of them. Once you fix that, the issue should go away.
The compiler is complaining that the vtable is not available. Vtable-s are an implementation detail, and thus not treated by the standard, but many compilers will generate the vtable in the translation unit that defines the first (non-inline) virtual function. In your case, whatever the criterion to generate the vtable is, you are not complying with it.
See what I wrote on the GCC wiki to explain undefined reference to vtable for X errors.
There are also loads of existing questions on SO about that linker error, I'm sure one of them has an answer that explains it, e.g. here or here
You declared, but didn’t define, the virtual destructor in BaseReader. You need to provide a definition for this in the .cpp file in order for the vtable for BaseReader to be generated. Same for CharReader.