为什么链接 sdl2 和 udev 会导致分段错误？

Question

我有以下非常愚蠢的 C 程序：

#include <SDL2/SDL.h>

int main () {
  SDL_Init(SDL_INIT_VIDEO);
}

如果我编译它并链接到sdl2，一切都很好：

[nix-shell:~/work/on-the-limit]$ gcc oddity.c -lSDL2 -o oddity

[nix-shell:~/work/on-the-limit]$ ./oddity 

但是，如果我也链接到 udev...

[nix-shell:~/work/on-the-limit]$ gcc oddity.c -lSDL2 -ludev -o oddity

[nix-shell:~/work/on-the-limit]$ ./oddity 
Segmentation fault

...发生分段错误。

gdb 有话要说：

[nix-shell:~/work/on-the-limit]$ gdb ./oddity 
GNU gdb (GDB) 7.10
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./oddity...done.
(gdb) run
Starting program: /home/ollie/work/on-the-limit/oddity 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/nix/store/npfsi1d9ka8zwnxzn3sr08hbwvpapyk7-glibc-2.21/lib/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff736b36a in strlen () from /nix/store/483br9kb3f5igsgmb6aqsjhl2ipj2bxr-glibc-2.21/lib/libc.so.6
(gdb) bt
#0  0x00007ffff736b36a in strlen () from /nix/store/483br9kb3f5igsgmb6aqsjhl2ipj2bxr-glibc-2.21/lib/libc.so.6
#1  0x00007ffff7fbb54b in strpcpy () from /nix/store/m3k7v0cy7zh6qbjqhrxgd36p105qqf0q-systemd-217/lib/libudev.so.1
#2  0x00007ffff7fbb6b3 in strscpy () from /nix/store/m3k7v0cy7zh6qbjqhrxgd36p105qqf0q-systemd-217/lib/libudev.so.1
#3  0x00007ffff7fb8f3d in device_new_from_parent.isra.7.lto_priv () from /nix/store/m3k7v0cy7zh6qbjqhrxgd36p105qqf0q-systemd-217/lib/libudev.so.1
#4  0x00007ffff7fb6140 in udev_device_get_parent () from /nix/store/m3k7v0cy7zh6qbjqhrxgd36p105qqf0q-systemd-217/lib/libudev.so.1
#5  0x00007ffff4c9b85a in loader_get_pci_id_for_fd () from /run/opengl-driver/lib/libGL.so.1
#6  0x00007ffff4c9be68 in loader_get_driver_for_fd () from /run/opengl-driver/lib/libGL.so.1
#7  0x00007ffff4c95126 in dri2CreateScreen () from /run/opengl-driver/lib/libGL.so.1
#8  0x00007ffff4c748d4 in __glXInitialize () from /run/opengl-driver/lib/libGL.so.1
#9  0x00007ffff4c70c1b in GetGLXPrivScreenConfig.part.2 () from /run/opengl-driver/lib/libGL.so.1
#10 0x00007ffff4c70d4d in glXChooseVisual () from /run/opengl-driver/lib/libGL.so.1
#11 0x00007ffff7b92288 in X11_GL_LoadLibrary () from /nix/store/qcf0jg20x3fnb09p4xc1y5dsbz84m7h9-SDL2-2.0.3/lib/libSDL2-2.0.so.0
#12 0x00007ffff7b89567 in SDL_CreateWindow_REAL () from /nix/store/qcf0jg20x3fnb09p4xc1y5dsbz84m7h9-SDL2-2.0.3/lib/libSDL2-2.0.so.0
#13 0x00007ffff7b89180 in SDL_VideoInit_REAL () from /nix/store/qcf0jg20x3fnb09p4xc1y5dsbz84m7h9-SDL2-2.0.3/lib/libSDL2-2.0.so.0
#14 0x00007ffff7ac8317 in SDL_Init_REAL () from /nix/store/qcf0jg20x3fnb09p4xc1y5dsbz84m7h9-SDL2-2.0.3/lib/libSDL2-2.0.so.0
#15 0x00000000004008b6 in main () at oddity.c:4

Answer 1

如果一个程序的行为仅取决于它的链接方式而有所不同，那么这一定是由于不同的函数实现在一种情况和另一种情况下[动态]链接。除此之外，要详细回答需要检查所有所涉及的库的详细信息。

尽管如此，在这一点上，我倾向于观察到您显然严重依赖 RPATH，这是非常值得怀疑的。尤其值得怀疑的是，您似乎是通过 RPATH 解析 C 标准库（从回溯的第一行可以明显看出）而不是使用系统的版本。

最好通过配置动态链接器来影响动态链接，而不是通过在程序或库中嵌入 RPATH。如果目标是使用与系统默认不同的库，那么您可能会发现建立一个可以运行您的程序的替代 chroot 环境很有用。在任何情况下，请确保编译器、静态链接器、动态链接器、程序所依赖的所有库以及程序本身都同意使用每个库的哪个版本。