pix_share_read crashes on render()

[avilleret]

here is a gdb backtrace :

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff3a6b164 in pix_share_read::render (this=0xb9d4d0, state=0x7fffffffb840) at pix_share_read.cpp:38
38        int csize=pix.image.setCsizeByFormat(h->format);
bt
#0  0x00007ffff3a6b164 in pix_share_read::render (this=0xb9d4d0, state=0x7fffffffb840) at pix_share_read.cpp:38
#1  0x00007ffff38b1dfa in GemBase::gem_renderMess (this=0xb9d4d0, cache=<optimized out>, state=0x7fffffffb840) at GemBase.cpp:154
#2  0x0000000000465c29 in pd_typedmess ()
#3  0x000000000046767a in outlet_anything ()
#4  0x00000000004af713 in trigger_anything ()
#5  0x0000000000465b5b in pd_typedmess ()
#6  0x000000000046767a in outlet_anything ()
#7  0x0000000000465b5b in pd_typedmess ()
#8  0x000000000046767a in outlet_anything ()
#9  0x0000000000465b5b in pd_typedmess ()
#10 0x0000000000465b5b in pd_typedmess ()
#11 0x000000000046767a in outlet_anything ()
#12 0x0000000000465b5b in pd_typedmess ()
#13 0x0000000000465b5b in pd_typedmess ()
#14 0x000000000046767a in outlet_anything ()
#15 0x00007ffff38b1d35 in GemBase::continueRender (this=0xb9b5d0, state=<optimized out>) at GemBase.cpp:167
#16 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0xb9b5d0, cache=<optimized out>, state=0x7fffffffb840) at GemBase.cpp:155
#17 0x0000000000465c29 in pd_typedmess ()
#18 0x000000000046767a in outlet_anything ()
#19 0x00007ffff38b1d35 in GemBase::continueRender (this=0xb5ee90, state=<optimized out>) at GemBase.cpp:167
#20 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0xb5ee90, cache=<optimized out>, state=0x7fffffffb840) at GemBase.cpp:155
#21 0x0000000000465c29 in pd_typedmess ()
#22 0x000000000046767a in outlet_anything ()
#23 0x00007ffff38b1d35 in GemBase::continueRender (this=0xb5ebe0, state=<optimized out>) at GemBase.cpp:167
#24 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0xb5ebe0, cache=<optimized out>, state=0x7fffffffb840) at GemBase.cpp:155
#25 0x0000000000465c29 in pd_typedmess ()
#26 0x000000000046767a in outlet_anything ()
#27 0x0000000000465b5b in pd_typedmess ()
#28 0x000000000046767a in outlet_anything ()
#29 0x0000000000465b5b in pd_typedmess ()
#30 0x0000000000465b5b in pd_typedmess ()
#31 0x000000000046767a in outlet_anything ()
#32 0x00007ffff3916936 in gemhead::renderGL (this=0xb9c220, state=0x7fffffffb840) at gemhead.cpp:160
#33 0x00007ffff3916c79 in gemhead::bangMess (this=0xb9c220) at gemhead.cpp:185
#34 0x0000000000467399 in outlet_bang ()
#35 0x0000000000467399 in outlet_bang ()
#36 0x0000000000463e39 in bindlist_bang ()
#37 0x0000000000467399 in outlet_bang ()
#38 0x00000000004af6c8 in trigger_anything ()
#39 0x0000000000465b5b in pd_typedmess ()
#40 0x000000000046767a in outlet_anything ()
#41 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7012cb0, state=<optimized out>) at GemBase.cpp:167
#42 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7012cb0, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#43 0x0000000000465c29 in pd_typedmess ()
#44 0x000000000046767a in outlet_anything ()
#45 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7013aa0, state=<optimized out>) at GemBase.cpp:167
#46 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7013aa0, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#47 0x0000000000465c29 in pd_typedmess ()
#48 0x000000000046767a in outlet_anything ()
#49 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7013c20, state=<optimized out>) at GemBase.cpp:167
#50 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7013c20, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#51 0x0000000000465c29 in pd_typedmess ()
#52 0x000000000046767a in outlet_anything ()
#53 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7013e70, state=<optimized out>) at GemBase.cpp:167
#54 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7013e70, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#55 0x0000000000465c29 in pd_typedmess ()
#56 0x000000000046767a in outlet_anything ()
#57 0x00007ffff38b1d35 in GemBase::continueRender (this=0x70140c0, state=<optimized out>) at GemBase.cpp:167
#58 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x70140c0, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#59 0x0000000000465c29 in pd_typedmess ()
#60 0x000000000046767a in outlet_anything ()
#61 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7012470, state=<optimized out>) at GemBase.cpp:167
#62 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7012470, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#63 0x0000000000465c29 in pd_typedmess ()
#64 0x000000000046767a in outlet_anything ()
#65 0x00007ffff38b1d35 in GemBase::continueRender (this=0x7012fd0, state=<optimized out>) at GemBase.cpp:167
#66 0x00007ffff38b1e05 in GemBase::gem_renderMess (this=0x7012fd0, cache=<optimized out>, state=0x7fffffffc200) at GemBase.cpp:155
#67 0x0000000000465c29 in pd_typedmess ()
#68 0x000000000046767a in outlet_anything ()
#69 0x00007ffff3916936 in gemhead::renderGL (this=0x70120d0, state=0x7fffffffc200) at gemhead.cpp:160
#70 0x00007ffff3916c79 in gemhead::bangMess (this=0x70120d0) at gemhead.cpp:185
#71 0x0000000000467399 in outlet_bang ()
#72 0x0000000000467399 in outlet_bang ()
#73 0x0000000000467399 in outlet_bang ()
#74 0x00000000004af6c8 in trigger_anything ()
#75 0x0000000000465b5b in pd_typedmess ()
#76 0x000000000046767a in outlet_anything ()
#77 0x0000000000465b5b in pd_typedmess ()
#78 0x0000000000465b5b in pd_typedmess ()
#79 0x000000000046767a in outlet_anything ()
#80 0x00000000004af713 in trigger_anything ()
#81 0x0000000000465b5b in pd_typedmess ()
#82 0x000000000046767a in outlet_anything ()
#83 0x0000000000465b5b in pd_typedmess ()
#84 0x000000000046767a in outlet_anything ()
#85 0x00000000004af713 in trigger_anything ()
#86 0x0000000000465b5b in pd_typedmess ()
#87 0x000000000046767a in outlet_anything ()
#88 0x0000000000465b5b in pd_typedmess ()
#89 0x0000000000465b5b in pd_typedmess ()
#90 0x000000000046767a in outlet_anything ()
#91 0x00007fffdd8301ad in routeOSC_doanything (x=0x7998670, s=0xca5bd0, argc=0, argv=0x7887980) at routeOSC.c:380
#92 0x0000000000465b5b in pd_typedmess ()
#93 0x000000000046767a in outlet_anything ()
#94 0x00007fffda735d2f in unpackOSC_list (x=0x7887930, s=<optimized out>, argc=<optimized out>, argv=<optimized out>) at unpackOSC.c:277
#95 0x00000000004675ea in outlet_list ()
#96 0x00007fffd9d212aa in iemnet__receiver_tick (x=0x7875fd0) at iemnet_receiver.c:148
#97 0x00007fffd9d21c7d in pollfun (z=<optimized out>, fd=<optimized out>) at iemnet_notify.c:126
#98 0x00000000004792ea in sys_domicrosleep.constprop.3 ()
#99 0x000000000047b0ea in sys_pollgui ()
#100 0x000000000047477a in m_mainloop ()
#101 0x00007ffff6e0476d in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#102 0x00000000004114d1 in _start ()
(gdb) 

is it possible that shm_addr is invalid but not NULL ?
Could a call of shmat(shm_id,NULL,0666); at each render cycle fix this ?
Does it make sense ? Is it efficienet ?
I'll give it a try (but double check this time before sending a pull request :-) )

A

[avilleret]

a call to shmat(shm_id,NULL,0666) on each render cycle doesn't seem to solve this issue
see my commit [1] in my branch fix_pix_share_read

[1} : https://github.com/avilleret/Gem/commit/e5821dab3f2a1127678d8d1cd8abdae8a29570ae

[umlaeute]

calling shmat() in each render cycle is almost certainly a bad idea esp if you don't call shmdt() as well: as i understand it shmat() will increment the reference counter, thus leaving you with un-freeable chunks of shared memory.