CODEWITHSUNDEEP
c++c++11headerinclusionheader-only
cppbeginner
cppbeginner

Reputation: 121

Double inclusion and headers only library stbi_image

I have a main.cpp including a.h (that has its own a.cpp) a.h includes the header only library "stbi_image.h" as such:

#ifndef STB_IMAGE_IMPLEMENTATION
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#endif

(https://github.com/nothings/stb)

*.cpp includes its own *.h with the use of #pragma once

But I still get:

LNK1169 one or more multiply defined symbols found LNK2005 stb-failure reason already defined in a.obj file = main.obj ... and a bunch of others

It seems right to me, but as I understand in this question: Multiple definition and header-only libraries

Maybe I should add inline/static to the stb_image.h function I need ? Am I doing something wrong?

Thanks in advance

Upvotes: 12

Views: 13417

Answers (2)

jhsheng
jhsheng

Reputation: 34

In addition to the solution mentioned by @Scheff's Cat below the question, I would like to point out the reason to do this.

STB_IMAGE_IMPLEMENTATION is not the protection for the header file. When STB_IMAGE_IMPLEMENTATION is enabled, you are actually inserting the corresponding implementation code in that file, so you cannot put it in a header .

Upvotes: 0

Valery S.
Valery S.

Reputation: 636

  1. Maybe I should add inline/static to the stb_image.h function I need ?

No, you already have a way to declare 'stb_image functions' as static or as extern:

#define STB_IMAGE_STATIC
  1. Am I doing something wrong ? Yes, you compile 'stb_image' twice, each time you include 'stb_image.h' So, the whole design could be:

Image.h:

#ifndef _IMAGE_H_
#define _IMAGE_H_

Class Image.h {
public:
    Image() : _imgData(NULL) {}
    virtual ~Image();
    ...
    void loadf(...);
    ...

    unsigned char* getData() const { return _imgData; }
protected:
    unsigned char* _imgData;
};
#endif

Image.cpp:

#include "Image.h"

#define STB_IMAGE_IMPLEMENTATION   // use of stb functions once and for all
#include "stb_image.h"

Image::~Image()
{ 
    if ( _imgData ) 
        stbi_image_free(_imgData); 
}

void Image::load(...) {
    _imgData = stbi_load(...);
}

main.cpp

#include "Image.h" // as you see, main.cpp do not know anything about stb stuff

int main() {
    Image* img = new Image();  // this is my 'wrapper' to stb functions
    img->load(...);

    myTexture(img->getData(), ...);

    return 0;
}

Upvotes: 11

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