Possibly FFI bug on ARM
- From: mike <mikhaeldanilov@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Tue, 07 Aug 2012 18:38:09 +0400
Hi,
FFI can lead to unaligned access exception, when working with packed
structures on ARM ( in my case OMAP3 ( beagleBoard xm), ubuntu 12.04 )
platform. ( on x86|x64 everything works fine )
Should this be considered FFI bug, or it is up to user to take care
about alignment issues on alignment sensitive platforms?
Code to reproduce case:
ffi = require "ffi"
ffi.cdef[[
typedef __attribute__ ((packed)) struct _tst
{
int8_t _byte;
int16_t _short;
int32_t _int;
}tst;
]]
tmp = ffi.new("tst");
tmp._byte = math.random() * 0xff; -- ok
tmp._short = math.random() * 0xffff; -- ok
tmp._int = math.random() * 0xffffffff; -- got SIGBUS here (
tmp._int = const works fine ( ?gets optimized out? ) )
print(tmp._byte); -- ok
print(tmp._short); -- ok
print(tmp._int); -- ok, ?or just optimized out?
P.S.
echo 2 > /proc/cpu/alignment
(tell linux kernel to fix alignment errors, more info:
http://www.mjmwired.net/kernel/Documentation/arm/mem_alignment )
do not helps, not sure is this a FFI, or linux kernel issue here...
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