Undefined symbols for architecture i386:

Question

I've recently moved over to a mac, and am struggling using the command line compilers. I'm using g++ to compile, and this builds a single source file fine. if I try to add a custom header file, when I try to compile using g++ I get undefined symbols for architecture i386. The programs compile fine in xCode however. Am I missing something obvious?

tried using g++ -m32 main.cpp... didn't know what else to try.

---

Okay, The old code compiled... Have narrowed it down to my constructors.

class Matrix{
public:
    int a;
    int deter;

    Matrix();
    int det();
};

#include "matrix.h"


Matrix::Matrix(){
    a = 0;
    deter = 0;
}

int Matrix::det(){
    return 0;

}

my error is Undefined symbols for architecture x86_64: "Matrix::Matrix()", referenced from: _main in ccBWK2wB.o ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status

my main code has

#include "matrix.h"
int main(){
    Matrix m;

    return 0;
} 

along with the usual

Solution 1

is not the case here, but it may happen to be the you forget to put the class name with ::

for example:

---

a good format:

foo.h

class Foo{
public:
    Foo();
    void say();
private:
    int x;
};

foo.cpp

Foo::Foo(){
    this->x = 1;
}

void Foo::say(){
    printf("I said!\n");
}

---

a bad format

foo.h

class Foo{
public:
    Foo();
    void say();
private:
    int x;
}

foo.cpp

Foo::Foo(){
    this->x = 1;
}

//I always mistake here because I forget to put the class name with :: and the xcode don't show this error.
void say(){
    printf("I said!\n");
}

Solution 2

Did you actually define the Box constructor somewhere? (like Line.cpp)

Comments

[RedX]

And you are missing a ; after the constructor declaration.

[maccard]

Constructor is defined. The code compiles in XCode. and no, have a ; at the end of that line, that's just a type sorry.

[Ken Aspeslagh]

and you're including Matrix.cpp in the command line too, right?

[maccard]

No, I wasn't including matrix.cpp in the command line. Thanks!

[2am]

wow, this one did it for me.. I'd say not enough c++ experience from my side. I thought the issue was with Xcode. But no, it was my mistake. Will be careful now.

[Can Ürek]

Perfect explain. Thanks.