#include conflict

Development
1

Hello,

(sorry for bad english, not a native speaker)

I have a function define in a header that I want to use in multiple modules of the same plug in, but when I try to use it I got compile error, “multiple definition”.

I have tried the trouble shooting I have found at this link with no success: Using dr_wav in more than one module - Development - VCV Community (vcvrack.com)

moving the #include to plugin.cpp, moving it to plugin.hpp, etc… I have even tried to put the header in the sdk include file, which works as long as I use the function in only one module

The header is protected with #pragma once and #ifndef

I may have made an error in c++, I’m pretty new to all of this, still struggling to understand everything about the linkers

Any ideas ?

(I’m on windows, compiling with Mingw64, apart from this, everything is working fine)

Thank you in advance for your help…

2

If your header file contains an implementation of the function, then you should not include it in multiple source files.

In the other thread that you linked, the header file has a mechanism using a #define to control whether it is included with an implementation or not. If your header has a mechanism like this, you need to ensure that exactly one of your source files includes the implementation.

1 Like
3

ok, thank you a lot !

I’m better understanding my mistake…

Is using the “inline” keyword ok, or would you recommend copying the function in each source file separately ?

4

With dr wave you can include it everywhere, but there is a define for the implementation that can only be in one file. I use this in my SFZ player, it works fine.

5

Are you trying to use dr_wave or was that just an example?

6

yep, here’s a place I used it. just make sure to only define DR_WAV_IMPLEMENTATION once.

#include "FlacReader.h"
#include "SqLog.h"
#include "WaveLoader.h"
#include "share/windows_unicode_filenames.h"

#define DR_WAV_IMPLEMENTATION
#include "dr_wav.h"

class LoaderBase : public WaveInfoInterface {
public:
(etc)

If you put the #define in more than one file, you will get the linker errors.

7

Sorry Bruce, i was asking the OP.

8

It was juste an example, it was the closest thread I have found, The header contain few tools that I have made and often use, for example mapping a value from -5/+5 to 0/10 (or any other values) I have tried with inline, it works, but I don’t know if it won’t create more problem in the long run

9

You can do a few things.

You can put the functions in a separate cpp file, and just put the function declarations in the header file. Then the linker will just find one definition/implementation.

Or you can wrap the function in an anonymous namespace. Then each source file that includes the header will get a unique version of the function, and the linker won’t complain about duplicates.

2 Likes
10

Or you can declare the functions inline, can’t you?

1 Like
11

Absolutely.

12

Thank you a lot for your help !

I’ll try all of this and stick with what seems the most optimal for me !