This is really puzzling me. I compiled the latest git from savannah, and this is what I get:

$ ldd /usr/bin/gtk-gnash  | grep libgcc_s.so.1
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f31c4ac7000)

$ /usr/bin/gtk-gnash anythingatall.swf
libgcc_s.so.1 must be installed for pthread_cancel to work

Using gdb to poke at it, when the thread aborts, I get this:

(gdb) bt
#0  0x00007ffff5250295 in raise () from /usr/lib/libc.so.6
#1  0x00007ffff52516da in abort () from /usr/lib/libc.so.6
#2  0x00007ffff528bd50 in __libc_message () from /usr/lib/libc.so.6
#3  0x00007ffff528bd92 in __libc_fatal () from /usr/lib/libc.so.6
#4  0x00007ffff788755f in pthread_cancel_init () from /usr/lib/libpthread.so.0
#5  0x00007ffff7887664 in _Unwind_ForcedUnwind () from /usr/lib/libpthread.so.0
#6  0x00007ffff7885cb0 in __pthread_unwind () from /usr/lib/libpthread.so.0
#7  0x00007ffff787e595 in pthread_exit () from /usr/lib/libpthread.so.0
#8  0x00007ffff43388b0 in ?? () from /usr/lib/libSDL-1.2.so.0
#9  0x00007ffff787d474 in start_thread () from /usr/lib/libpthread.so.0
#10 0x00007ffff530469d in clone () from /usr/lib/libc.so.6


(gdb) info threads
  Id   Target Id         Frame
  1    Thread 0x7fffe20199c0 (LWP 988) "gtk-gnash" 0x00007ffff787e6bd in pthread_join () from /usr/lib/libpthread.so.0
* 2    Thread 0x7fffe171f700 (LWP 992) "gtk-gnash" (Exiting) 0x00007ffff5250295 in raise () from /usr/lib/libc.so.6


(gdb) thread 1
[Switching to thread 1 (Thread 0x7fffe20199c0 (LWP 988))]


(gdb) bt
#0  0x00007ffff787e6bd in pthread_join () from /usr/lib/libpthread.so.0
#1  0x00007ffff42f71e6 in SDL_WaitThread () from /usr/lib/libSDL-1.2.so.0
#2  0x00007ffff42eef8a in SDL_AudioQuit () from /usr/lib/libSDL-1.2.so.0
#3  0x00007ffff42ede65 in SDL_QuitSubSystem () from /usr/lib/libSDL-1.2.so.0
#4  0x00007ffff7fc82cf in gnash::sound::SDL_sound_handler::closeAudio (this=0x555555621ba0) at sdl/sound_handler_sdl.cpp:101
#5  gnash::sound::SDL_sound_handler::initAudio (this=0x555555621ba0) at sdl/sound_handler_sdl.cpp:63
#6  gnash::sound::SDL_sound_handler::SDL_sound_handler (this=0x555555621ba0, m=<optimized out>) at sdl/sound_handler_sdl.cpp:111
#7  0x00007ffff7fc8311 in gnash::sound::create_sound_handler_sdl (m=0x5555555cf440) at sdl/sound_handler_sdl.cpp:236
#8  0x000055555558ec37 in gnash::Player::init_sound (this=this@entry=0x7fffffffcf50) at Player.cpp:282
#9  0x000055555559160b in gnash::Player::run (this=0x7fffffffcf50, argc=2, argv=<optimized out>, infile=..., url=...) at Player.cpp:454
#10 0x00005555555700d0 in playFile (player=..., argc=2, argv=0x7fffffffe728, filename="banned from equestria daily.swf") at gnash.cpp:92
...

so... what's going on?