Incomprehensible LNK1169 error

First, here's a class definition and some associated functions inside a header names "phonemes.h"

It's very long so don't look at it all. Just the final "operator-" definition is causing the problem. I just posted the entire code just in case something in there that I'd overlooked was causing the problem.

Code:

#ifndef _PHONEMES_H__INCLUDED_
#define _PHONEMES_H__INCLUDED_

#include "main_header.h"

struct core_features{
	UINT cons			:1;	//consonantal
	UINT syll			:1;	//syllabic
	UINT son			:1;	//sonorant
	UINT lab			:1;	//labial
	UINT cor			:1;	//coronal
	UINT back			:1;	//back
};

struct secondary_features
{
	UINT ant			:1;	//anterior
	UINT dist			:1;	//distributed
	UINT high			:1;	//high
	UINT low			:1;	//low
	UINT voice			:1;	//voiced
	UINT spread			:1;	//spread glottis
	UINT constr			:1;	//constricted glottis
	UINT cont			:1;	//continuant
	UINT del_rel		:1;	//delayed release
	UINT lat			:1;	//lateral
	UINT nas			:1;	//nasal
	UINT atr			:1;	//advanced tongue root
};

struct ternary_features
{
	UINT spread			:1;
	UINT atr			:1;
};


class Phoneme{
protected:
	core_features c_feat;
	secondary_features s_feat;
	UCHAR uc_c_feat;
	WCHAR wc_s_feat;
public:
	Phoneme(){*(PUCHAR)(&c_feat) = 0; *(PWCHAR)(&s_feat) = 0; uc_c_feat = 0; wc_s_feat = 0;}
	~Phoneme(){}
	void set_cons(int i = 1){c_feat.cons = i; UCHAR k = 1; i ? uc_c_feat |= (1 << 5) : ((k <<=5) & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_syll(int i = 1){c_feat.syll = i; UCHAR k = 1; i ? uc_c_feat |= (1 << 4) : ((k <<=4) & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_son(int i = 1){c_feat.son = i; UCHAR k = 1; i ? uc_c_feat |= (1 << 3) : ((k <<=3) & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_lab(int i = 1){c_feat.lab = i; UCHAR k = 1; i ? uc_c_feat |= (1 << 2) : ((k <<=2) & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_cor(int i = 1){c_feat.cor = i; UCHAR k = 1; i ? uc_c_feat |= (1 << 1) : ((k <<=1) & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_back(int i = 1){c_feat.back = i; UCHAR k = 1; i ? uc_c_feat |= 1 : (k & uc_c_feat ? uc_c_feat ^= k : 0);}
	void set_ant(int i = 1){s_feat.ant = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 11) : ((k <<= 11) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_dist(int i = 1){s_feat.dist = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 10) : ((k <<= 10) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_high(int i = 1){s_feat.high = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 9) : ((k <<= 9) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_low(int i = 1){s_feat.low = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 8) : ((k <<= 8) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_voice(int i = 1){s_feat.voice = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 7) : ((k <<= 7) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_spread(int i = 1){s_feat.spread = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 6) : ((k <<= 6) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_constr(int i = 1){s_feat.constr = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 5) : ((k <<= 5) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_cont(int i = 1){s_feat.cont = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 4) : ((k <<= 4) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_del_rel(int i = 1){s_feat.del_rel = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 3) : ((k <<= 3) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_lat(int i = 1){s_feat.lat = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 2) : ((k <<= 2) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_nas(int i = 1){s_feat.nas = i; WCHAR k = 1; i ? wc_s_feat |= (1 << 1) : ((k <<= 1) & wc_s_feat ? wc_s_feat ^= k : 0);}
	void set_atr(int i = 1){s_feat.atr = i; WCHAR k = 1; i ? wc_s_feat |= 1 : (k & wc_s_feat ? wc_s_feat ^= k : 0);}
	core_features* p_c_feat(){return &c_feat;}
	secondary_features* p_s_feat(){return &s_feat;}
	UCHAR uc_c_feat_value(){return uc_c_feat;}
	WCHAR wc_s_feat_value(){return wc_s_feat;}
	virtual void initialize(){*(PUCHAR)(&c_feat) = 0; *(PWCHAR)(&s_feat) = 0;}
	//friend operator-(Phoneme&, Phoneme&);
};

class Vowel : public Phoneme
{
public:
	Vowel()
	{
		*(PUCHAR)(&c_feat) = 0;
		*(PWCHAR)(&s_feat) = 0;
		this->set_son();
		this->set_syll();
		this->set_cont();
		this->set_voice();		
	}
	~Vowel(){}
	virtual void initialize()
	{
		*(PUCHAR)(&c_feat) = 0;
		*(PWCHAR)(&s_feat) = 0;
		this->set_son();
		this->set_syll();
		this->set_cont();
		this->set_voice();
	}
};

class Consonant : public Phoneme
{
public:
	Consonant()
	{
		*(PUCHAR)(&c_feat) = 0;
		*(PWCHAR)(&s_feat) = 0;
		this->set_cons();
	}
	~Consonant(){}
	virtual void initialize()
	{
		*(PUCHAR)(&c_feat) = 0;
		*(PWCHAR)(&s_feat) = 0;
		this->set_cons();
	}
};

inline int bit_diff(UINT i, UINT j)
{
	i ^= j;
	int result = 0;
	for(; i > 0; i >>= 1)
		i & 1 ? result++ : 0;
	return result;
}

template<class T>
inline int bit_diff_t(T i, T j)
{
	i ^= j;
	T result = 0;
	for(; i > 0; i >>= 1)
		i & 1 ? result++ : 0;
	return result;

}


//Commenting out this function gets rid of the problem.
int operator-(Phoneme& p1, Phoneme& p2)
{
	//return 10 * bit_diff(*((PUINT) p1.p_c_feat()), *((PUINT) p2.p_c_feat())) + bit_diff(*((PUINT) p1.p_s_feat()), *((PUINT) p2.p_s_feat()));
	return 10 * bit_diff_t<UCHAR>(p1.uc_c_feat_value(), p2.uc_c_feat_value()) + bit_diff_t<WCHAR>(p1.wc_s_feat_value(), p2.wc_s_feat_value());
}

#endif

The error message I get when I compile is as follows:

Code:

OT_OK error LNK2005: "int __cdecl operator-(class Phoneme &,class Phoneme &)" (??G@YAHAAVPhoneme@@0@Z) already defined in main.obj
OT_OK fatal error LNK1169: one or more multiply defined symbols found

The strange thing is, when I move that "operator-" function out of the header and into the cpp file containing the main routine, it compiles just fine.
What am I doing wrong?

Don't define non-inline methods inside a header file (even one with include guards). Either mark it as inline, or define it in a single cpp file. The problem is that multiple cpp files are including that header, which is allowed for declarations. However, each cpp file is compiling that function separately and the linker is finding multiple definitions.

That solved it. Thanks a gesundheit.