Hi all,
I’m running into a strange problem when trying to use Mono 4.4.1.0 on an ARM
architecture.
When I try to execute a Mono application or simply run mcs, I get the following
output:
# mcs
* Assertion at unwind.c:385, condition `read16 (p) == (guint32)(op->when -
loc)' not met
Stacktrace:
Native stacktrace:
Debug info from gdb:
=================================================================
Got a SIGABRT 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
The same application and mcs work fine with Mono 4.0.2, I used a while ago.
Looking at the source code in mono/mini/unwind.c in function
mono_unwind_ops_encode_full, I can see that the code tries to cast a pointer to
a guint16 or guint32 pointer, which will fail on (my) ARM when the address is
not aligned (lines 378 and 384).
} else if (op->when - loc > 256) {
*p ++ = DW_CFA_advance_loc2;
*(guint16*)p = (guint16)(op->when - loc);
g_assert (read16 (p) == (guint32)(op->when - loc));
What is interesting, is that the g_assert is using the read16 macro, which
deals with alignment issues and also endianness. But with this, I can’t really
see how the code would work successfully with big endianness either.
The code in question hasn’t changed between 4.0 and 4.4 but the pointer casting
is only executed when “op->when - loc > 256” is true. So I wonder why this
changed for me between 4.0 and 4.4 and if I’m even supposed to run into these
cases on an ARM architecture? When I fix the two problems, everything seems to
run fine.
Because I don’t think that I’m the first to try to execute “mcs” or run a Mono
application on an ARM architecture, I kind of blame my build system. I use
buildroot and run my system on an ARM 926 device. Unfortunately, I have no idea
what the code in mono_unwind_ops_encode_full actually does and when op->when -
loc would actually be greater than 256.
I hope that someone here could give me some pointers on why the if condition
could be true and never was before or in fact is not true for any ARM device,
so I can check my build system.
Thanks,
Henry_______________________________________________
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