[Mono-dev] Possible bug when using array of unsafe pointers

Mon Apr 13 19:15:21 UTC 2015

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This bug exists on Ubuntu and I think osx too. As a workaround I
stored Intpr's of the struct in a list.

On 13.04.2015 20:44, Fabian Nagel wrote:
> Dear Devs,
> 
> I tried to port my .NET C# application to run on Linux (Fedora21)
> through Mono, but it crashes somewhere in the runtime's garbage
> collector code with segmentation fault. The minimal code to
> reproduce the problem is as follows: SomeStruct*[] ptrs = new
> SomeStruct*[1]; ptrs[0] = (SomeStruct*)Marshal.AllocHGlobal(4); 
> GC.Collect();
> 
> Here some further information:
> 
> [fabian at localhost Debug]$ mono --version Mono JIT compiler version
> 3.12.1 (tarball Fri Mar  6 18:53:33 GMT 2015) Copyright (C)
> 2002-2014 Novell, Inc, Xamarin Inc and Contributors. 
> www.mono-project.com TLS:           __thread SIGSEGV:
> altstack Notifications: epoll Architecture:  amd64 Disabled:
> none Misc:          softdebug LLVM:          supported, not
> enabled. GC:            sgen
> 
> Stacktrace:
> 
> at <unknown> <0xffffffff> at (wrapper managed-to-native)
> System.GC.InternalCollect (int) <IL 0x0000d, 0xffffffff> at
> System.GC.Collect () [0x00000] in 
> /builddir/build/BUILD/mono-3.12.1/mcs/class/corlib/System/GC.cs:51 
> at MMC.Benchmarks.MOT.TestTable (int,bool) [0x00010] in 
> /home/fabian/Documents/New 
> folder/MemoryContext/Benchmarks/MemoryOperationsTest.cs:227 at
> MMC.Program.Main (string[]) [0x0050d] in
> /home/fabian/Documents/New folder/MemoryContext/Program.cs:379 at
> (wrapper runtime-invoke) <Module>.runtime_invoke_void_object 
> (object,intptr,intptr,intptr) <IL 0x00050, 0xffffffff>
> 
> Native stacktrace:
> 
> mono() [0x4b46c2] mono() [0x50c893] mono() [0x42ab73] 
> /lib64/libpthread.so.0(+0x100d0) [0x7f9bba5050d0] 
> /lib64/libc.so.6(+0x145e42) [0x7f9bba066e42] mono() [0x5dd2f3] 
> mono() [0x5dd581] mono() [0x5ddd98] mono() [0x5d2d08] mono()
> [0x5d2f0f] mono() [0x5d4715] mono() [0x5d5212] mono() [0x5d87d0] 
> mono(mono_gc_collect+0x28) [0x5d9078] [0x40337eb2]
> 
> Debug info from gdb:
> 
> warning: File "/usr/bin/mono-sgen-gdb.py" auto-loading has been
> declined by your `auto-load safe-path' set to
> "$debugdir:$datadir/auto-load". To enable execution of this file
> add add-auto-load-safe-path /usr/bin/mono-sgen-gdb.py line to your
> configuration file "/home/fabian/.gdbinit". To completely disable
> this security protection add set auto-load safe-path / line to your
> configuration file "/home/fabian/.gdbinit". For more information
> about this security protection see the "Auto-loading safe path"
> section in the GDB manual.  E.g., run from the shell: info
> "(gdb)Auto-loading safe path" [New LWP 27513] [Thread debugging
> using libthread_db enabled] Using host libthread_db library
> "/lib64/libthread_db.so.1". 0x00007f9bba504c6b in waitpid () from
> /lib64/libpthread.so.0 Id   Target Id         Frame 2    Thread
> 0x7f9bb18ec700 (LWP 27513) "Finalizer" 0x00007f9bb9f55cc7 in 
> sigsuspend () from /lib64/libc.so.6 * 1    Thread 0x7f9bbb021780
> (LWP 27512) "mono" 0x00007f9bba504c6b in waitpid () from
> /lib64/libpthread.so.0
> 
> Thread 2 (Thread 0x7f9bb18ec700 (LWP 27513)): #0
> 0x00007f9bb9f55cc7 in sigsuspend () from /lib64/libc.so.6 #1
> 0x00000000005cf99c in suspend_handler () #2  <signal handler
> called> #3  0x00007f9bba50370e in sem_wait () from
> /lib64/libpthread.so.0 #4  0x0000000000625587 in mono_sem_wait () 
> #5  0x00000000005a7fcd in finalizer_thread () #6
> 0x000000000058c370 in start_wrapper () #7  0x000000000062a466 in
> inner_start_thread () #8  0x00007f9bba4fc52a in start_thread ()
> from /lib64/libpthread.so.0 #9  0x00007f9bba02122d in clone () from
> /lib64/libc.so.6
> 
> Thread 1 (Thread 0x7f9bbb021780 (LWP 27512)): #0
> 0x00007f9bba504c6b in waitpid () from /lib64/libpthread.so.0 #1
> 0x00000000004b474f in mono_handle_native_sigsegv () #2
> 0x000000000050c893 in mono_arch_handle_altstack_exception () #3
> 0x000000000042ab73 in mono_sigsegv_signal_handler () #4  <signal
> handler called> #5  0x00007f9bba066e42 in __memcpy_avx_unaligned ()
> from /lib64/libc.so.6 #6  0x00000000005dd2f3 in
> copy_object_no_checks () #7  0x00000000005dd581 in
> major_copy_or_mark_object () #8  0x00000000005ddd98 in
> major_scan_object () #9  0x00000000005d2d08 in
> sgen_drain_gray_stack () #10 0x00000000005d2f0f in
> job_scan_from_registered_roots () #11 0x00000000005d4715 in
> major_copy_or_mark_from_roots () #12 0x00000000005d5212 in
> major_do_collection () #13 0x00000000005d87d0 in
> sgen_perform_collection () #14 0x00000000005d9078 in
> mono_gc_collect () #15 0x0000000040337eb2 in ?? () #16
> 0x00000000014ad120 in ?? () #17 0x00007ffd488929e0 in ?? () #18
> 0x0000000000000000 in ?? ()
> 
> ================================================================= 
> Got a SIGSEGV while executing native code. This usually indicates a
> fatal error in the mono runtime or one of the native libraries used
> by your application. 
> =================================================================
> 
> Aborted (core dumped)
> 
> 
> Thanks, Fabi
> 
> 
> 
> _______________________________________________ Mono-devel-list
> mailing list Mono-devel-list at lists.ximian.com 
> http://lists.ximian.com/mailman/listinfo/mono-devel-list
> 

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