I want to make a game using SDL2, but I'm unable to compile and/or run my code, please help!
SDL2 is notoriously hard to set up, and it's often the first library aspiring game developers try to use.
This post is intended as a canonical duplicate for common problems with setting up SDL2.
This answer is about MinGW / GCC, and not Visual Studio.
This answer only applies to Windows.
Common errors
The common errors are:
SDL.h: No such file or directory (when compiling)
Various SDL_main problems: "undefined reference to SDL_main", "conflicting types for SDL_main" or "number of arguments doesn't match prototype", etc. (when compiling or linking)
undefined reference to other functions (when linking)
DLL problems: (when running your program)
'??.dll' was not found
procedure entry point ... could not be located in ..., and other mysterious DLL-related errors
The program seemingly doing nothing when launched
This list is sorted from bad to good. If you change something and get a different error, use this list to tell if you made things better or worse.
The preamble
0. Don't follow bad advice.
Some resources will suggest you to do #define SDL_MAIN_HANDLED or #undef main. Don't blindly follow that advice, it's not how SDL2 is intended to be used.
If you do everything correcty, it will never be necessary. Learn the intended approach first. Then you can research what exactly that does, and make an educated decision.
1. Figure out how to compile directly from the console, you can start using an IDE and/or build system later.
If you're using an IDE, I suggest to first make sure you're able to compile your program directly from the console, to rule out any IDE configuration problems. After you figure that out, you can use the same compiler options in your IDE.
The same applies to build systems, such as CMake.
2. Download the right SDL2 files. Make sure you have the right files. You need the archive called SDL2-devel-2.0.x-mingw.tar.gz from here.
Extract it to any directory, preferably somewhere near your source code. Extracting into the compiler installation directory is often considered a bad practice (and so is copying them to C:\Windows, which is a horrible idea).
3. Know the difference between compiler flags and linker flags. A "flag" is an option you specify in the command line when building your program. When you use a single command, e.g. g++ foo.cpp -o foo.exe, all your flags are added to the same place (to this single command).
But when you build your program in two steps, e.g.:
g++ foo.cpp -c -o foo.o (compiling)
g++ foo.o -o foo.exe (linking)
you have to know which of the two commands to add a flag to. Those are "compiler flags" and "linker flags" respectively.
Most IDEs will require you to specify compiler and linker flags separately, so even if you use a single command now, it's good to know which flag goes where.
Unless specified otherwise, the order of the flags doesn't matter.
SDL.h: No such file or directory
Or any similar error related to including SDL.h or SDL2/SDL.h.
You need to tell your compiler where to look for SDL.h. It's in the SDL files you've downloaded (see preamble).
Add -Ipath to your compiler flags, where path is the directory where SDL.h is located.
Example: -IC:/Users/HolyBlackCat/Downloads/SDL2-2.0.12/x86_64-w64-mingw32/include/SDL2. Relative paths work too, e.g. -ISDL2-2.0.12/x86_64-w64-mingw32/include/SDL2.
Note that the path will be different depending on how you write the #include:
If you do #include <SDL.h>, then the path should end with .../include/SDL2 (like above). This is the recommended way.
If you do #include <SDL2/SDL.h>, then the path should end with .../include.
Various SDL_main problems
You can get several different errors mentioning SDL_main, such as undefined reference to SDL_main, or conflicting types for 'SDL_main', or number of arguments doesn't match prototype, etc.
You need to have a main function. Your main function must look like int main(int, char **). NOT int main() and NOT void main(). This is a quirk of SDL2, related to it doing #define main SDL_main.
Adding parameter names is allowed (and is mandatory in C), e.g. int main(int argc, char **argv). Also the second parameter can be written as char *[] or with a name: char *argv[]. No other changes are allowed.
If your project has multiple source files, make sure to include SDL.h in the file that defines the main function, even if it doesn't otherwise use SDL directly.
Try to avoid #define SDL_MAIN_HANDLED or #undef main when solving this issue, see preamble for explanation.
undefined reference to various functions
• undefined reference to SDL_...
The error message will mention various SDL_... functions, and/or WinMain. If it mentions SDL_main, consult the section "Various SDL_main problems" above. If the function names don't start with SDL_, consult the section "undefined reference to other functions" below.
You need to add following linker flags: -lmingw32 -lSDL2main -lSDL2 -Lpath, where path is the directory where libSDL2.dll.a and libSDL2main.a (which you've downloaded) are located. The order of the -l... flags matters. They must appear AFTER any .c/.cpp/.o files.
Example: -LC:/Users/HolyBlackCat/Desktop/SDL2-2.0.12/x86_64-w64-mingw32/lib. Relative paths work too, e.g. -LSDL2-2.0.12/x86_64-w64-mingw32/lib.
When you use -l???, the linker will look for a file called lib???.dll.a or lib???.a (and some other variants), which is why we need to pass the location of those files. libmingw32.a (corresponding to -lmingw32) is shipped with your compiler, so it already knows where to find it.
I added all those flags and nothing changed, or I'm getting skipping incompatible X when searching for Y:
You probably use the wrong SDL .a files. The archive you downloaded contains two sets of files: i686-w64-mingw32 (32-bit) and x86_64-w64-mingw32 (64-bit). You must use the files matching your compiler, which can also be either 32-bit or 64-bit.
Print (8*sizeof(void*)) to see if your compiler is 32-bit or 64-bit.
Even if you think you use the right files, try the other ones to be sure.
Some MinGW versions can be switched between 32-bit and 64-bit modes using -m32 and -m64 flags (add them to both compiler and linker flags).
I get undefined reference to a specific function:
• undefined reference to WinMain only
There are several possibilities, all of which were covered in the previous section:
You forgot -lmingw32 and/or -lSDL2main linker flags.
You must use following linker flags, in this exact order, after
any .c/.cpp/.o files: -lmingw32 -lSDL2main -lSDL2
The libSDL2main.a file you use doesn't match your compiler (32-bit file with a 64-bit compiler, or vice versa).
Try to avoid #define SDL_MAIN_HANDLED or #undef main when solving this issue, see preamble for explanation.
• undefined reference to SDL_main only
See the section "Various SDL_main problems" above.
• undefined reference to other functions
Your linker found and used libSDL2.a, but it should be finding and using libSDL2.dll.a. When both are available, it prefers the latter by default, meaning you didn't copy the latter to the directory you passed to -L.
If you intended to perform static linking, see the section called "How do I distribute my app to others?" below.
Nothing happens when I try run my app
Let's say you try to run your app, and nothing happens. Even if you try to print something at the beginning of main(), it's not printed.
Windows has a nasty habit of not showing some DLL-related errors when the program is started from the console.
If you were running your app from the console (or from an IDE), instead try double-clicking the EXE in the explorer. Most probably you'll now see some DLL-related error; then consult one of the next sections.
??.dll was not found
Copy the .dll mentioned in the error message, and place it next to your .exe.
If the DLL is called SDL2.dll, then it's in the SDL files you've downloaded (see preamble). Be aware that there are two different SDL2.dlls: a 32-bit one (in the i686-w64-mingw32 directory), and a 64-bit one (in x86_64-w64-mingw32). Get the right one, if necessary try both.
Any other DLLs will be in your compiler's bin directory (the directory where gcc.exe is located).
You might need to repeat this process 3-4 times, this is normal.
For an automatic way of determining the needed DLLs, see the next section.
procedure entry point ... could not be located in ... and other cryptic DLL errors
Your program needs several .dlls to run, and it found a wrong version of one, left over from some other program you have installed.
It looks for DLLs in several different places, but the directory with the .exe has the most priority.
You should copy all DLLs your program uses (except the system ones) into the directory where your .exe is located.
A reliable way to get a list of needed DLLs is to blindly copy a bunch of DLLs, and then remove the ones that turn out to be unnecessary:
Copy SDL2.dll. It's in the SDL files you've downloaded (see preamble). Be aware that there are two different SDL2.dlls: a 32-bit one (in the i686-w64-mingw32 directory), and a 64-bit one (in x86_64-w64-mingw32). Get the right one, if necessary try both.
Copy all DLLs from your compiler's bin directory (the directory where gcc.exe is located).
Now your program should run, but we're not done yet.
Download NTLDD (or some other program that displays a list of used DLLs). Run ntldd -R your_program.exe.
Any DLL not mentioned in its output should be removed from the current directory. Your program uses everything that remains.
I ended up with following DLLs, expect something similar: SDL2.dll, libgcc_s_seh-1.dll, libstdc++-6.dll (C++ only), libwinpthread-1.dll.
Can I determine the needed DLLs without copying excessive ones?
Yes, but it's less reliable.
Your program searches for DLLs in following locations, in this order:
The directory where your .exe is located.
C:\Windows, including some of its subdirectories.
The directories listed in PATH.
Assuming you (or some jank installer) didn't put any custom DLLs into C:\Windows, adding your compiler's bin directory to the PATH (preferably as the first entry) and either putting SDL2.dll in the same directory as the .exe or into some directory in the PATH should be enough for your program to work.
If this works, you can then run ntldd without copying any DLLs beforehand, and copy only the necessary ones. The reason why you'd want to copy them at all at this point (since your app already works) is to be able to distribute it to others, without them having to install the compiler for its DLLs. Skip any DLLs located outside of your compiler's bin directory (except for SDL2.dll).
Note that the possibility of having weird DLLs in C:\Windows is real. E.g. Wine tends to put OpenAL32.dll into C:\Windows, so if you try this process with OpenAL on Wine, it will fail. If you're making a sciprt that runs ntldd automatically, prefer copying the DLLs (or at least symlinking them - I heard MSYS2 can emulate symlinks on Windows?).
Can I make an EXE that doesn't depend on any DLLs?
It's possible to make an .exe that doesn't depend on any (non-system) .dlls by using the -static linker flag, this is called "static linking". This is rarely done, and you shouldn't need to do this if you did the above steps correctly. This requires some additional linker flags; they are listed in file ??-w64-mingw32/lib/pkgconfig/sdl2.pc shipped with SDL, in the Libs.private section. Notice that there are two files, for x32 and x64 respectively.
How do I distribute my app to others?
Follow the steps in the previous section, titled procedure entry point ... could not be located in ....
A saner alternative?
There is MSYS2.
It has a package manager that lets you download prebuilt libraries, and, as a bonus, a fresh version of the compiler.
Install SDL2 from its package manager. Use a tool called pkg-config (also from the package manager) to automatically determine all necessary flags (pkg-config --cflags SDL2 for compiler flags, pkg-config --libs SDL2 for linker flags).
This is the same experience as you would have on Linux (maybe except for some DLL management hassle).
Bonus - Other problems
Q: My program always opens a console window when I run it, how do I hide it?
A: Add -mwindows to the linker flags.
Q: I get error 'SDL_VideoMode' wasn't declared in this scope.
A: SDL_VideoMode is from SDL1.2, it's not a part of the newer SDL2. Your code was written for the outdated version of SDL. Find a better tutorial that deals specifically with SDL2.
Q: My program has the default file icon, but I want a custom one.
A: Your icon must be in the .ico format. If your graphics editor doesn't support it, make a series of .pngs of common sizes (e.g. 16x16, 32x32, 48x48, 64x64), then convert them to a single .ico using ImageMagick: magick *.png result.ico (or with convert instead of magick).
Create a file with the .rc extension (say, icon.rc), with following contents MyIconName ICON "icon.ico" (where MyIconName is an arbitrary name, and "icon.ico" is the path to the icon). Convert the file to an .o using windres -O res -i icon.rc -o icon.o (the windres program is shipped with your compiler). Specify the resulting .o file when linking, e.g. g++ foo.cpp icon.o -o foo.exe.
Recent versions of SDL2 have a nice property of using the same icon as the window icon, so you don't have to use SDL_SetWindowIcon.
A solution for Visual Studio:
Why not use a package manager? I use vcpkg, and it makes super easy to consume 3rd party libraries. Grab the vcpkg source, and extract it to a safe place, like C:/, then run its bootstrap script bootstrap-vcpkg.bat, this will generate vcpkg executable. Then run vcpkg integrate install to make libraries installed with vcpkg available in Visual Studio.
Search for the library you need:
vcpkg search sdl
imgui[sdl2-binding] Make available SDL2 binding
libwebp[vwebp-sdl] Build the vwebp viewer tool.
magnum[sdl2application] Sdl2Application library
sdl1 1.2.15#12 Simple DirectMedia Layer is a cross-platform development library designed to p...
sdl1-net 1.2.8-3 Networking library for SDL
sdl2 2.0.12-1 Simple DirectMedia Layer is a cross-platform
...
Install it with: vcpkg install sdl2.
Now you just need include SDL2 headers, and everything will work out of the box. The library will be linked automatically.
You can learn more about vcpkg here.
On Mac this is what I follow for XCode (must install g++):
sdl linking:
g++ main.cpp -o main $(sdl2-config --cflags --libs)
XCODE project steps:
open terminal app (macOS)
BUILD SETTINGS (select 'all' and 'combined' search bar enter: "search")
click on "header search paths(way right side click)
add: /usr/local/include
BUILD PHASES --> LINK BINARY LIBRARIES (click plus)
type in SDL --> click "add other"
press: command+SHIFT+g (to bring search bar)
type in: usr/local/Cellar
navigate to: SDL2 -->2.0.8 -->lib --> libSDL2-2.2.0.dylib (make sure not shortcut)
I'm trying to compile a C program (specifically, the Python interpreter) as a plain statically linked 64-bit Windows binary. My command line looks like this:
cl /DPy_BUILD_CORE ... /link Advapi32.lib Shell32.lib User32.lib
where ... is the long list of source files and include directory specifications, and the library specifications I added as necessary to fix unresolved symbol errors. I'm getting linker output that looks like (after the C compiler has finished running):
Microsoft (R) Incremental Linker Version 12.00.21005.1
Copyright (C) Microsoft Corporation. All rights reserved.
/out:getbuildinfo.exe
Advapi32.lib
Shell32.lib
User32.lib
getbuildinfo.obj
(lots more .obj's)
Creating library getbuildinfo.lib and object getbuildinfo.exp
... and then a weird error that I'm still trying to figure out, but maybe I might have a better chance if I understand another aspect of the behavior of the linker here.
Why is it creating a library? I didn't tell it to do that. It's only supposed to be creating a .exe.
In particular, I tried a small test case with just a couple of trivial C source files and otherwise the exact same command line, and it behaved as expected, creating only the .exe and not trying anything with libraries. The only differences are in the number and contents of the C source files, but I wouldn't have thought the contents of a C source file could change the behavior of the linker.
What am I missing?
I am trying to compile a simple C Windows API program using the Windows SDK Command Prompt.
Here an excerpt from the program:
#include <Windows.h>
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
[...]
RegisterClass(&wc);
hwnd = CreateWindow("test", NULL, 0, 0, 0, 0, 0, NULL, NULL, hInstance, NULL);
[...]
When I compile it using
cl test.c
in the Windows SDK Command Promt, it gives me a lot of linker errors like these:
test.obj : error LNK2019: unresolved external symbol __imp_CreateWindowExA referenced in function WinMain
test.obj : error LNK2019: unresolved external symbol __imp_RegisterClassA referenced in function WinMain
There are at least two problems.
The linker is telling you that there is an "unresolved external symbol". That means it can't find a definition for the function(s) that you tried to call. In this case, there are two such undefined functions: CreateWindowExA and RegisterClassA.
Obviously the definition for those functions is not to be found in your code, but rather in the Windows API libraries, so you'll need to inform the linker of where it can find those definitions.
The SDK comes with stubs (*.lib) files, which contain information used by the linker so that it can find the proper function definitions in the Windows DLLs at runtime. You need to instruct the linker where it can find those *.lib files.
There are a couple of different strategies for doing so:
The simple (albeit non-portable) way is to insert a #pragma statement into your source file that instructs the compiler to leave a comment recognized by the linker. For example,
#pragma comment(lib, "user32")
automatically links to user32.lib, which is the stub file for user32.dll.
Alternatively, you can pass the parameters on the command line to cl.exe. This gets awfully complicated in a hurry, though, if you're not using MSBuild or some kind of make file. In this case, you would need to modify your command line to (at minimum):
cl test.c user32.lib
Both of these options naturally assumes that your Windows SDK directory was added to the path. I'm pretty sure the installer does that for you automatically, but I'm not positive. If it doesn't, or you've removed these files from your path, you'll need to use fully-qualified paths to the *.lib files on the command line.
Reading the documentation for the possible compiler options is a good place to start. Or better yet, if you're unfamiliar with Windows programming, using an environment like Visual Studio that puts all of this stuff together for you automatically. Once you understand what's going on, look to see what the command line that Visual Studio runs is, and dissect it bit-by-bit.
Next problem is that you're compiling without Unicode defined, and because ANSI is the default, all of the macros inside the Windows header files are resolving to call the A suffixed versions of all the SDK functions. This is probably not what you want. Windows has been fully Unicode now for over a decade, and all new applications should be built as Unicode. The Unicode versions have a W suffix appended to their name.
Again, you can instruct the compiler to build with Unicode explicitly by either adding lines to your source file, or adding parameters to your command line.
In this case, the simplest way is probably just to add
#define UNICODE
to the top of your source file before #include <windows.h>. Just as we saw above, from the Visual Studio environment, UNICODE is automatically defined for you unless you explicitly change your project settings to target something else.
Those functions live in user32.lib. You need to supply that to the cl tool.
cl test.c ""C:\Program Files\Microsoft SDKs\Windows\v6.0A\Lib\user32.lib"
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 15.00.307
Copyright (C) Microsoft Corporation. All rights reserved.
test.c
Microsoft (R) Incremental Linker Version 9.00.30729.01
Copyright (C) Microsoft Corporation. All rights reserved.
/out:test.exe
test.obj
"C:\Program Files\Microsoft SDKs\Windows\v6.0A\Lib\user32.lib"
I am making a kernel in Visual C++ according to to the tutorial here. However, when I try to build it I receive the error LINK : fatal error LNK1146: no argument specified with option '/OUT:'. I would provide source code, but it is unnecessary because I haven't changed it from the tutorial. However, for quick reference, here are my C/C++ options:
/Gd /Fm /TC /c kernel.c
And here is my Link options:
/safeseh:no /filealign:0x1000 /BASE:0x100000 /ENTRY:__multiboot_entry__ /NODEFAULTLIB:LIBC /SUBSYSTEM:CONSOLE /OUT: kernel.exe
No space after the colon:
/OUT:kernel.exe
I'm integrating .NET support into our C++ application.
It's an old-school MFC application, with 1 extra file compiled with the "/clr" option that references a CWinFormsControl.
I'm not allowed to remove the linker flag "/NODEFAULTLIB".
(We have our own build management system, not Visual Studio's.)
This means I have to specify all necessary libraries: VC runtime and MFC.
Other compiler options include "/MD"
Next to that: I can't use the linker flag "/FORCE:MULTIPLE" and just add everything:
I'm looking for a non-overlapping set of libraries.
As a bare minimum:
mscoree.lib
MSVCRT.lib
mfc90.lib (adjust version appropriately)
And iterate from there.
Use the AppWizard to create a bare-bones MFC app in your style (SDI / MDI / dialog ) and then put on your depends.
How I solved it:
link with "/FORCE:MULTIPLE /verbose" (that links ok) and set the output aside.
link with "/NODEFAULTIB /verbose" and trace all unresolveds in the output of the previous step and add the libraries 1 by 1.
This resulted in doubles: "AAA.lib: XXX already defined in BBB.lib"
Then I finally got it:
Recompiled managed AND unmanaged units with /MD
and link to (among others):
mscoree.lib
msvcmrt.lib
mfcm80d.lib
Mixing /MT (unmanaged) and /MD (managed) turned out to be the bad idea:
different(overlapping) libraries are needed.
#ajryan: Dependcy Walker only tells me what dll's are used, not what libraries are linked to when linking.
(e.g. msvcmrt.lib ?)
I think.
Thanks for the answers!
Jan