Python exception from negative shift

[davidmalcolm]

cpychecker fails with the appended Python stack trace when compiling gdb.

I think that the user should never see a Python exception. However, in this case I also think that the underlying error is erroneous. {{{ ../../archer/gdb/arm-tdep.c: In function ‘cleanup_block_load_all’: ../../archer/gdb/arm-tdep.c:6586:22: error: Unhandled Python exception raised calling 'execute' method Traceback (most recent call last): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/init.py", line 64, in execute self._check_refcounts(fun) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/init.py", line 68, in _check_refcounts self.show_possible_null_derefs) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/refcounts.py", line 2838, in check_refcounts limits=limits) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2716, in iter_traces depth + 1): File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2680, in iter_traces transitions = curstate.get_transitions() File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 1828, in get_transitions return self._get_transitions_for_stmt(stmt) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 1855, in _get_transitions_for_stmt return self._get_transitions_for_GimpleAssign(stmt) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2308, in _get_transitions_for_GimpleAssign value = self.eval_rhs(stmt) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 2251, in eval_rhs c = a.eval_binop(stmt.exprcode, b, stmt.lhs.type, stmt.loc) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 453, in eval_binop newvalue = eval_binop(exprcode, self.value, rhs.value) File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 365, in eval_binop result = inner() File "/home/tromey/Space/Trunk/gcc-python-plugin/libcpychecker/absinterp.py", line 354, in inner return a << b ValueError: negative shift count }}}

[davidmalcolm]

Imported from trac issue 14. Created by tromey on 2012-01-04T15:53:22, last modified: 2012-01-06T17:21:27

[davidmalcolm]

Trac comment by dmalcolm on 2012-01-05 14:40:03:

The root cause is similar to that of ticket #25

Minimal reproducer: {{{ int test(int i, int j) { return i << j; } }}}

j is WithinRange(-INT_MAX, INT_MAX), and this leads to the << barfing.

The fix would seem to be to split the range up into valid and non-valid ranges before doing the shift, analogous to how we do NULL vs non-NULL pointer-handling, I think.

[davidmalcolm]

Trac comment by dmalcolm on 2012-01-06 17:21:27:

Fixed in 3c6e7c7a33e3fb026ee1206ef8ebc9e1a5301062