Error LNK2005 in C++ and ifndef don't work - c++

Question

I have a problem with Visual Studio 2012 & 2015 about the fact than it's seem than the "ifndef" don't work. I use the "ifndef" for "NAN" and "ifndef" for the header file and it's said these 2 errors (see the image). When I add the link "#include"Outil.h"" in the header of other file, I see the same message of error.
I always do like this before and it's always work. I don’t understand why it's doesn't work now even with only two files.
I also try to change the name of the first function "realoc_ungraded" but it's doesn't work and I get the same error.
Message of error
The message:
1) Warning: C4005: 'NAN': macro redefinition of math.h
2) Error: LNK2005: "struct tab_dynamo __cdecl realoc_ugraded(struct tab_dynamo,unsigned int)" (?realoc_ugraded##YA?AUtab_dynamo##U1#I#Z) already defined in main.obj Project1
3) Error: LNK1169: one or more multiply defined symbols found Projet
There is the code of the different file:
File main.cpp
#include"Outil.h"
int main(void) {
return 0;
}
File Outil.h
#ifndef LIBRARY_OF_TOOLS
#define LIBRARY_OF_TOOLS 0
#define _USE_MATH_DEFINES
//NAN not defined in Visual Studio 2012, so I use the def. of VS 2015
#ifndef NAN
#define NAN ((float)(std::numeric_limits<float>::infinity*0.0F))
#endif
#include<iostream>
#include<string>
using namespace std;
#include<cmath>
#include<stdlib.h>
#include<stdio.h>
#include<assert.h>
#define ERROR_ADRESSE 0xcccccccc //default when not initialised
#define DEFAULT_LENGHT_TAB 1
//-----------------------------------------
typedef double type_data; //the type for calculation
//-----------------------------------------
/*Struct for my array*/
typedef struct {
type_data *tab;
unsigned int length;
}tab_dynamo;
//-----------------------------------------
template<typename T>
bool verify_ptr(const T *ptr) {
return (ptr == NULL || ptr == (T*)(ERROR_ADRESSE));
}
//-----------------------------------------
template<typename T>
void see_tab(const T *tab, const unsigned int taille) {
unsigned int i;
cout << endl << endl;
if (verify_ptr(tab) == false && taille > 0) {
cout << endl;
for (i = 0; i<taille; ++i) {
cout << tab[i] << "\t";
}
}
cout << endl << endl;
}
//-----------------------------------------
template<typename T>
T* realoc_ungraded(const T* original_tab, unsigned int *length, const unsigned int new_length) {
T* new_tab = NULL;
unsigned int precedent_length = 0, i;
/*1) Exception case to directly exit*/
if (new_length == 0) {
return NULL;
}
/*2) Verification of the ptr of the length*/
if (verify_ptr(length)) {
length = (unsigned int*)calloc(1, sizeof(unsigned int));
assert(length);
}
precedent_length = *length;
*length = new_length;
/*4) Creation of the new tab.*/
new_tab = (T*)calloc(*length, sizeof(T));
assert(new_tab);
/*5) To transfert data of the original tab to the new tab*/
if (precedent_length != 0 && verify_ptr(original_tab) == false) {
for (i = 0; i < precedent_length && i < new_length; ++i) {
new_tab[i] = original_tab[i];
}
}
return new_tab;
}
//-----------------------------------------
//Version with the use of the struct "tab_dynamo"
tab_dynamo realoc_ungraded(tab_dynamo original_tab, const unsigned int new_length) {
tab_dynamo tableau = { NULL, 0 };
tableau.tab = realoc_ugraded(original_tab.tab, &original_tab.length, new_length);
tableau.length = new_length;
return tableau;
}
#endif
File Outil.cpp:
#include"Outil.h"

Answer 1

#ifndef NAN
#define NAN ((float)(std::numeric_limits<float>::infinity*0.0F))
#endif
When preprocessor process these, the NAN is defined because it's not defined yet.
#include<cmath>
Then cmath maybe include math.h, and found NAN is defined by yours.
You can try to change the sequence of include and your definition.
#include <cmath>
#ifndef NAN
#define NAN ((float)(std::numeric_limits<float>::infinity*0.0F))
#endif
B.T.W If you compile using gcc, you could use -E option to see the output of preprocessor and know how the preprocess expand the macros.