unresolved external symbol __imp__fprintf and __im

Question

Could someone explain what the

__imp__fprintf

and

__imp____iob_func

unresolved external means?

Because I get these errors when I'm trying to compile:

1>SDL2main.lib(SDL_windows_main.obj) : error LNK2019: unresolved external symbol __imp__fprintf referenced in function _ShowError
1>SDL2main.lib(SDL_windows_main.obj) : error LNK2019: unresolved external symbol __imp____iob_func referenced in function _ShowError
1>E:\Documents\Visual Studio 2015\Projects\SDL2_Test\Debug\SDL2_Test.exe : fatal error LNK1120: 2 unresolved externals

I can already say that the problem is not from linking wrong. I have linked everything up correctly, but for some reason it won't compile.

I'm trying to use SDL2.

I'm using Visual Studio 2015 as compiler.

I have linked to SDL2.lib and SDL2main.lib in Linker -> Input -> Additional Dependencies and I have made sure that the VC++ Directories are correct.

Answer 1

A more recent solution to this problem: Use the more recent sdl libs on

"https://buildbot.libsdl.org/sdl-builds/sdl-visualstudio/?C=M;O=D"

They seem to have fixed the problem, although it's only the 32 bit library (I think).

Answer 2

This can happen when you link to msvcrt.dll instead of msvcr10.dll (or similar), which is a good plan. Because it will free you up to redistribute your Visual Studio's runtime library inside your final software package.

That workaround helps me (at Visual Studio 2008):

#if _MSC_VER >= 1400
#undef stdin
#undef stdout
#undef stderr
extern "C" _CRTIMP extern FILE _iob[];
#define stdin   _iob
#define stdout  (_iob+1)
#define stderr  (_iob+2)
#endif

This snippet is not needed for Visual Studio 6 and its compiler. Therefore the #ifdef.

Answer 3

I don't know why but:

#ifdef main
#undef main
#endif

After the includes but before your main should fix it from my experience.

Answer 4

Microsoft has a special note on this (https://msdn.microsoft.com/en-us/library/bb531344.aspx#BK_CRT):

The printf and scanf family of functions are now defined inline.

The definitions of all of the printf and scanf functions have been moved inline into stdio.h, conio.h, and other CRT headers. This is a breaking change that leads to a linker error (LNK2019, unresolved external symbol) for any programs that declared these functions locally without including the appropriate CRT headers. If possible, you should update the code to include the CRT headers (that is, add #include ) and the inline functions, but if you do not want to modify your code to include these header files, an alternative solution is to add an additional library to your linker input, legacy_stdio_definitions.lib.

To add this library to your linker input in the IDE, open the context menu for the project node, choose Properties, then in the Project Properties dialog box, choose Linker, and edit the Linker Input to add legacy_stdio_definitions.lib to the semi-colon-separated list.

If your project links with static libraries that were compiled with a release of Visual C++ earlier than 2015, the linker might report an unresolved external symbol. These errors might reference internal stdio definitions for _iob, _iob_func, or related imports for certain stdio functions in the form of __imp_*. Microsoft recommends that you recompile all static libraries with the latest version of the Visual C++ compiler and libraries when you upgrade a project. If the library is a third-party library for which source is not available, you should either request an updated binary from the third party or encapsulate your usage of that library into a separate DLL that you compile with the older version of the Visual C++ compiler and libraries.

Answer 5

To Milan Babuškov, IMO, this is exactly what the replacement function should look like :-)

FILE _iob[] = {*stdin, *stdout, *stderr};

extern "C" FILE * __cdecl __iob_func(void)
{
    return _iob;
}

Answer 6

I had the same issue in VS2015. I have solved it by compiling the SDL2 sources in VS2015.

1. Go to http://libsdl.org/download-2.0.php and download SDL 2 source code.
2. Open SDL_VS2013.sln in VS2015. You will be asked to convert the projects. Do it.
3. Compile SDL2 project.
4. Compile SDL2main project.
5. Use the new generated output files SDL2main.lib, SDL2.lib and SDL2.dll in your SDL 2 project in VS2015.