[Gc] Collection from unknown thread with iOS simulator

Joa Ebert joaebert at gmail.com
Tue Mar 12 12:03:20 PST 2013


I am running into some issues with the iPhone simulator when using the GC
7.2 and 7.2d. Basically the issue is that I get a "Collecting from unknown
thread" error.

First of all the GC is configured with

LDFLAGS="-arch i386 -isysroot $SDK_LIB -Wl,-syslibroot $SDK_LIB"

./configure --disable-dependency-tracking --host=arm-apple-darwin
--enable-cplusplus --enable-static --disable-shared
--enable-thread-local-alloc --enable-parallel-mark
--enable-threads=pthreads --prefix=/Users/joa/Development/libgc

I am also running into the issue when I specify --enable-threads=posix.
This is how I include the header files:

#define GC_THREADS
#define GC_NOT_DLL

#include <gc/gc.h>
#include <gc/gc_cpp.h>

When the program starts I do call GC_INIT(). So from this perspective
everything should be fine. But unfortunately the simulator spawns a thread
that is not tracked by the GC causing this error.

I have tried several solutions like GC_use_threads_discovery before GC_INIT
without success. This ends in SIGABRT with "Darwin task-threads-based stop
and push unsupported".

The operating system is Mac OS X 10.6 and the simulator uses SDK version
4.3 in case that matters for you.

This is the trace of the offending thread as it seems:

#0  0x90aa20ee in __semwait_signal_nocancel ()
#1  0x90aa1fd2 in nanosleep$NOCANCEL$UNIX2003 ()
#2  0x90b1cfb2 in usleep$NOCANCEL$UNIX2003 ()
#3  0x90b3e6f0 in abort ()
#4  0x00268f64 in GC_abort ()
#5  0x0026f9ee in GC_push_all_stacks ()
#6  0x0026a78b in GC_default_push_other_roots ()
#7  0x002678c9 in GC_push_roots ()
#8  0x00263d32 in GC_mark_some ()
#9  0x0025990a in GC_stopped_mark ()
#10 0x00259726 in GC_try_to_collect_inner ()
#11 0x0025ac48 in GC_collect_or_expand ()
#12 0x00261351 in GC_alloc_large ()
#13 0x00261896 in GC_generic_malloc ()
#14 0x00261e2e in GC_malloc_uncollectable ()
#25 0x90a62259 in _pthread_start ()
#26 0x90a620de in thread_start ()

I remember that I already had the collector working on an actual device a
while ago so I am a little bit confused about what is going on here.
Any help is greatly appreciated!


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