I am migrating from Java to C++. It seems that C++ makes classes declaration in separate files, difficult. So I need your help,
in my main.cpp:
#include "Sphere.h"
using namespace std;
.....
...
..
int main( void ) {
Sphere *earth = new Sphere(sphere_start ,sphere_end);
...
..
.
in my Sphere.h
class Sphere
{
public:
Sphere(int,int);
}
and in my Sphere.cpp
#include "Sphere.h"
using namespace std;
int sphere_start, sphere_end;
Sphere::Sphere (int a, int b)
{
sphere_start = a;
sphere_end = b;
}
void Sphere::render(int i)
{
....
..
.
}
This is the very basic code that I think causes the following error:
main.cpp:14:20: fatal error: Sphere.h: No such file or directory
compilation terminated.
why?
You need to add to your compile command a path to where the header files can be found.
If your header is in the headers directory add -Iheaders:
g++ -o main.o -c -Iheaders main.cpp
g++ -o sphere.o -c -Iheaders sphere.cpp
g++ -o app main.o sphere.o -L.
Or whatever your files are ...
Sphere.h must either be in the same directory as each file that includes it, or the compiler must be directed to search the directory in which Sphere.h is located.
You should post your command line, but my guess is that you should tell the path to the header files to the compiler. If you're using linux try this:
g++ main.cpp shpere.cpp -I<path_to_Sphere.h> -o main
Two potential errors:
Is Sphere.h in the same directory as main.cpp?
Is Sphere.h named Sphere.h and not sphere.h?
Related
I'm trying to build a simple program where I defined a class and included it's header in Main. While linking, Linker complains about accessing any of the member function from class:
: undefined reference to voxel::anyFunction
even though functions are public and headers are included.
Originally I discovered the problem when creating an object of voxel - I had overloaded the default constructor, but I figure out the problem is present for any function from voxel class.
Here are some code excerpts:
voxel.hpp
class voxel
{
public:
//here defined some member variables
//ommited the constructor
void fillMemberValuesWithDummy();//sets all members to some dummy value
};
voxel.cpp
#include "voxel.hpp"
void voxel::fillMemberValuesWithDummy()
{
//does the assignment to member variables
}
Main.cpp
#include <iostream>
#include <fstream>
using namespace std;
#include "voxel.hpp"
{
voxel someVoxel;
somevoxel.fillMemberValuesWithDummy();
}
I figure it is something very stupid I am (not) doing here, but can you tell me what?
You need to link all object files to get the executable. When you have just your two source files you can compile them directly:
g++ -o myprog.exe Main.cpp voxel.cpp
When you want to divide compile and link and do it this way:
g++ -c -o Main.o Main.cpp
g++ -c -o voxel.o voxel.cpp
g++ -o myprog.exe Main.o voxel.o
Feel free to create an appropriate Makefile that generates such commands.
Remove the .exe if you OS doesn't need it.
I have the following class called "Wav" which is stored in another directory, with the files "Wav.h" and "Wav.cpp" and looks like the following:
enum ReadType {
NATIVE = 0,
DOUBLE,
};
namespace AudioLib {
class Wav : public Signal {
public:
Wav();
Wav(const int M, const int N);
///... ->
};
};
The .cpp file contains the implementation of this class, everything compiles well.
I'm trying to implement a Python wrapper using boost.python and have the following file:
#include <boost/python.hpp>
#include "../src/Wav/Wav.h"
using namespace boost::python;
BOOST_PYTHON_MODULE(Wav)
{
class_<AudioLib::Wav>("Wav",
init<const int, const int>());
}
In my Makefile, I am compiling the Wav.cpp:
# Compile the .wav Python and Cpp file
$(WAV_TARGET).so: $(WAV_TARGET).o
g++ -shared -Wl,--export-dynamic $(WAV_TARGET).o -L$(BOOST_LIB) -lboost_python -
lboost_python -L/usr/lib/python$(PYTHON_VERSION)/config -lpython$(PYTHON_VERSION) -o
$(WAV_TARGET).so
$(WAV_TARGET).o: $(WAV_TARGET).cpp
g++ $(CFLAGS) ../src/Wav/Wav.cpp -I$(PYTHON_INCLUDE) -I$(BOOST_INC) -fPIC -c
$(WAV_TARGET).cpp
And whenever I try to import into Python I get the following:
ImportError: Wav.so: undefined symbol: _ZN8AudioLib3WavC1Eii
Where am I going wrong?
It looks like you have failed to define the second constructor:
Wav(const int M, const int N);
I can replicate the error message by making a working (but simplified) copy of your example with in-line definitions and just removing the definition of that constructor. So my advice would be to check carefully for the definition in Wav.cpp and try creating an in-line definition to experiment.
If the definition does exist, maybe the linker flags are not right.
Now when I try to compile main.cpp, I get an error as Undefined symbol add(int) in module main.cpp Please help me!
//main.cpp
#include<iostream.h>
#include "addition.h"
int main()
{
add(4);
return (0);
}
//add.cpp
#include "addition.h"
#include<iostream.h>
void add(int a)
{
cout<<a<<endl;
}
//addition.h
void add(int a);
The problem is that main() uses add(). And add is defined in another compilation unit (add.cpp) which is why you get the error message Undefined symbol add(int).
You need to tell the compiler to compile both pieces of code and link them together:
The easy way:
g++ main.cpp add.cpp
The long way:
# 1 Make the main object file
g++ -c main.cpp
# 2 Make the add object file
g++ -c add.cpp
# Link the object files into an executable.
g++ main.o add.o
I have problem and no idea how to resolve it. I believe this is stupid trivial:
I have 3 files:
Util.hpp
class Util
{
public:
class BitParser
{
public:
static bool getBitAt(int buf, int idx);
};
};
Util.cpp
#include "Util.hpp"
bool Util::BitParser::getBitAt(int buf, int idx)
{
return true;
}
application.cpp
#include "Util.hpp"
int main(int argc, char* argv[])
{
Util::BitParser::getBitAt(1,1);
}
Of couse, files listed above are in the same directory. And now when I try to link and compile I recieve linker error:
$ g++ -o app application.cpp
application.cpp:(.text+0x19): undefined reference to `Util::BitParser::getBitAt(int, int)'
collect2: ld returned 1 exit status
What is screwed up?
You told g++ to compile your 'main' program, but didn't tell it about the Util module. Add Util.cpp to the command line and all should work well.
The compiler has brewn an "application.o" file that refers to the Util::bitparser functions.
The linker should 'link' these referrals to the "util.o" file, containing the actual code for these functions. But it has no .o file containing a function satisfying the link. That's what it calls "undefined reference": "application.o" refers to a function the linker doesn't find.
You need to compile (and link) all the .cpp files. So in your case, the command would be
$ g++ -o app application.cpp Util.cpp
Better still, write a Makefile to do this for you.
You have to include both application.cpp and Util.cpp in the build.
I am getting the error message below when I try to compile my code -
In function
'__static_initialization_and_destruction_0':
home/user/main.cpp:50: undefined
reference to
'PhysEng2D::PhysEng2D(void)'
The only code on line 50 is -
PhysEng2D Physics;
The header file for PhysEng2D is -
#ifndef _PHYSENG2D_H_
#define _PHYSENG2D_H_
#include "primitives.h"
class PhysEng2D
{
public:
PhysEng2D::PhysEng2D();
PhysEng2D::~PhysEng2D();
bool IsBoundingBoxCollision(PS2Sprite & S1, PS2Sprite & S2);
bool IsWallCollision(PS2Sprite & S);
};
#endif
And the beginning of the rest of PhysEng2D is -
#include "primitives.h"
#include "physeng2d.h"
PhysEng2D::PhysEng2D()
{
//Nothing to Initialise
}
PhysEng2D::~PhysEng2D()
{
//Nothing to clean up
}
(I didn't include the methods in full because I didn't think they were relevant)
Sorry, I am aware that this is probably a very stupid little error that I'm making.
Your constructor and destructor in the header file should not contain the name of the class.
Change
PhysEng2D::PhysEng2D();
PhysEng2D::~PhysEng2D();
To
PhysEndg2D();
~PhysEng2D();
And you don't need to reinclude "primitives.h" in the .cpp.
You need to compile each cpp file, then link them.
g++ -c -Wall main.cpp
g++ -c -Wall physeng2d.cpp
g++ -o myapp main.o physeng2d.o
You also should remove the PhysEng2D:: prefix from the class definition in the .h
It looks like you forgot to link PhysEng2D.o with main.o. Also PhysEng2D::PhysEng2D(); syntax isn't valid inside the class definition: It should just say PhysEng2D();.