SDL2 pulls lots of dependencies

Game Development
1

I was really surprised how much memory my simple 3D (openGL) program is using so I looked at pmap of my process and found a lot of unneeded libraries loaded

00007fe958000000   65536      20      20 rw-s- memfd:pulseaudio (deleted)
00007fe95c000000   65536       0       0 rw-s- memfd:pulseaudio (deleted)
00007fe960000000   65536       0       0 rw-s- memfd:pulseaudio (deleted)
00007fe964000000     132       4       4 rw---   [ anon ]
00007fe964021000   65404       0       0 -----   [ anon ]
00007fe968000000   65536       0       0 rw-s- memfd:pulseaudio (deleted)
00007fe96c000000     132       4       4 rw---   [ anon ]
00007fe9947cb000      16      16       0 r---- libvorbis.so.0.4.9
00007fe9947cf000      88      64       0 r-x-- libvorbis.so.0.4.9
00007fe9947e5000      68       0       0 r---- libvorbis.so.0.4.9
00007fe9947f6000       4       0       0 ----- libvorbis.so.0.4.9
00007fe9947f7000       4       4       4 r---- libvorbis.so.0.4.9
00007fe9947f8000       4       4       4 rw--- libvorbis.so.0.4.9
00007fe9947f9000       4       0       0 -----   [ anon ]
00007fe9ac010000      12      12       0 r---- libopus.so.0.8.0
00007fe9ac013000     276      60       0 r-x-- libopus.so.0.8.0
00007fe9ac058000      76       0       0 r---- libopus.so.0.8.0
00007fe9ac06b000       4       0       0 ----- libopus.so.0.8.0
00007fe9ac06c000       4       4       4 r---- libopus.so.0.8.0
00007fe9ac06d000       4       4       4 rw--- libopus.so.0.8.0
00007fe9ac06e000      36      36       0 r---- libFLAC.so.8.3.0
00007fe9ac077000     164      64       0 r-x-- libFLAC.so.8.3.0
00007fe9ac0a0000      40       0       0 r---- libFLAC.so.8.3.0
00007fe9ac0aa000       4       0       0 ----- libFLAC.so.8.3.0
00007fe9ac0ab000       4       4       4 r---- libFLAC.so.8.3.0
00007fe9ac0ac000       4       4       4 rw--- libFLAC.so.8.3.0
00007fe9ac0ad000      80      80       0 r---- libvorbisenc.so.2.0.12
00007fe9ac0c1000      12      12       0 r-x-- libvorbisenc.so.2.0.12
00007fe9ac0c4000     476       0       0 r---- libvorbisenc.so.2.0.12
00007fe9ac13b000     112     112     112 r---- libvorbisenc.so.2.0.12
00007fe9ac157000       4       4       4 rw--- libvorbisenc.so.2.0.12
00007fe9ac158000      28      28       0 r---- libsndfile.so.1.0.31
00007fe9ac15f000     344      64       0 r-x-- libsndfile.so.1.0.31
00007fe9ac1b5000     124       0       0 r---- libsndfile.so.1.0.31
00007fe9ac1d4000      12      12      12 r---- libsndfile.so.1.0.31
00007fe9ac1d7000       4       4       4 rw--- libsndfile.so.1.0.31
00007fe9ac1d8000       8       0       0 rw---   [ anon ]
00007fe9ac1da000      84      84       0 r---- libpulsecommon-15.0.so
00007fe9ac1ef000     288     288       0 r-x-- libpulsecommon-15.0.so
00007fe9ac237000     160     100       0 r---- libpulsecommon-15.0.so
00007fe9ac25f000      12      12      12 r---- libpulsecommon-15.0.so
00007fe9ac262000       4       4       4 rw--- libpulsecommon-15.0.so
00007fe9ac263000      52      52       0 r---- libpulse.so.0.24.0
00007fe9ac270000     188     188       0 r-x-- libpulse.so.0.24.0
00007fe9ac29f000      88      64       0 r---- libpulse.so.0.24.0
00007fe9ac2b5000       8       8       8 r---- libpulse.so.0.24.0
00007fe9ac2b7000       4       4       4 rw--- libpulse.so.0.24.0
00007fe9ac2b8000    2048       0       0 rw-s- renderD128
00007fe9ac4b8000    2048       0       0 rw-s- renderD128
00007fe9ac6b8000       4       0       0 -----   [ anon ]
00007fe9b68aa000      84      84       0 r---- libvulkan.so.1.2.203
00007fe9b68bf000     248     128       0 r-x-- libvulkan.so.1.2.203
00007fe9b68fd000     128      64       0 r---- libvulkan.so.1.2.203
00007fe9b691d000      12      12      12 r---- libvulkan.so.1.2.203
00007fe9b6920000       4       4       4 rw--- libvulkan.so.1.2.203
00007fe9b6921000       8       8       0 r---- libdrm_nouveau.so.2.0.0
00007fe9b6923000      16      16       0 r-x-- libdrm_nouveau.so.2.0.0
00007fe9b6927000       8       0       0 r---- libdrm_nouveau.so.2.0.0
00007fe9b6929000       4       4       4 r---- libdrm_nouveau.so.2.0.0
00007fe9b692a000       4       4       4 rw--- libdrm_nouveau.so.2.0.0

This is just a snippet, but as you can see I have a lot of audio related libs (even though I don’t have any audio yet) and even a vulkan library. Why is that ? Is there a way to prevent that ?
Here’s ldd output just in case

	linux-vdso.so.1 (0x00007ffcf01a5000)
	libSDL2-2.0.so.0 => /usr/lib/libSDL2-2.0.so.0 (0x00007f0b595b7000)
	libm.so.6 => /usr/lib/libm.so.6 (0x00007f0b59473000)
	libGL.so.1 => /usr/lib/libGL.so.1 (0x00007f0b593ed000)
	libc.so.6 => /usr/lib/libc.so.6 (0x00007f0b59221000)
	libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f0b5921a000)
	libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f0b591f9000)
	/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007f0b598de000)
	libGLdispatch.so.0 => /usr/lib/libGLdispatch.so.0 (0x00007f0b5913f000)
	libGLX.so.0 => /usr/lib/libGLX.so.0 (0x00007f0b5910c000)
	libX11.so.6 => /usr/lib/libX11.so.6 (0x00007f0b58fca000)
	libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00007f0b58fa0000)
	libXau.so.6 => /usr/lib/libXau.so.6 (0x00007f0b58f9b000)
	libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00007f0b58f93000)
2

I could only reproduce this when I used SDL_INIT_AUDIO flag so if you’re not using audio yet don’t pass the flag to SDL_Init.

3

SDL uses libpulse for audio output, I think the other audio libs get pulled in by libpulse (possibly via libpulsecommon)

4

So is there no way to avoid it even if I don’t want to use these formats, for example FLAC or ogg ? Also, what’s up with the vulkan and libdrm_nouveau ? I have AMD card so why would i have nouveau loaded ?

Also, since this library pulls in GLX.so (my compilation flags below) how do I use openGL with SDL2 on Wayland ? Do I need to build another binary for Wayland ? I just noticed it now.

LIBS="\
    -lcimgui
    -L../cimgui/
    -lSDL2 \
    -lm \
    -lGL \
"
5

So is there no way to avoid it even if I don’t want to use these formats, for example FLAC or ogg ?

No, but this is not an SDL issue but a pulseaudio issue.

Also, what’s up with the vulkan and libdrm_nouveau ? I have AMD card so why would i have nouveau loaded ?

No idea, but this is also is something that certainly isn’t SDL2’s fault (it doesn’t even know about nouveau), but Mesas. Probably libGL(X) or libvulkan or whatever

Do I need to build another binary for Wayland ?

Currently SDL2 uses X11 by default, so on Wayland it uses xwayland.
To actually use the Wayland backend you have to enforce it by setting the environment variable SDL_VIDEODRIVER=wayland.
In the next SDL2 release (or the current git code if you build SDL2 yourself), it will use the native Wayland backend by default if you’re on Wayland.

6

Is it possible to build one binary that will work both on X11 and Wayland ? Since right now when I just link to -GL i also get GLX

7

You don’t have to link against libGL at all.
You can use an OpenGL loader like glad with SDL_GL_GetProcAddress - SDL Wiki (call gladLoadGLLoader(SDL_GL_GetProcAddress); after creating the OpenGL context) to get the OpenGL functions without having to link libGL or GLX yourself.

Instead of glad there’s also gl3w which I think could be used with gl3wInit2((GL3WGetProcAddressProc)SDL_GL_GetProcAddress); - most other OpenGL function loaders I looked at (like glew) seem to use glx/wgl directly instead of letting the user provide a function pointer to SDL_GL_GetProcAddress() (or equivalent functions).

1 Like
8

Thanks ! I will try that.
EDIT: It works. Same binary works both on Wayland and X11 with Glad :slight_smile:

1 Like