[Python-Dev] troubling math bug under IRIX 6.5

[Flying Cougar Burnette]

Tim Peters writes:
|
| > now neither does.  shall I turn opts back on and try a few more
| > cases?
| 
| Yes, please, one more:
| 
|     4.0 * 3.1
| 
| Or, if that works, go back to the failing
| 
|     4.0 * math.exp(-0.5)

both of these work, but changing the 4.0 to an integer 4 produces the
bus error.  so it is definitely a conversion to double/float thats
the problem.

| 
| In any failing case, can you jump into a debubber and get a stack trace?

sure.  I've included an entire dbx session at the end of this mail.

| 
| Do you happen to have
| 
|     WANT_SIGFPE_HANDLER
| 
| #define'd when you compile Python on this platform?  If so, it complicates
| the code a lot.  I wonder about that because you got a "bus error", and when
| WANT_SIGFPE_HANDLER is #defined we get a whole pile of ugly setjmp/longjmp
| code that doesn't show up on my box.

a peek at config.h shows the WANT_SIGFPE_HANDLER define commented
out.  should I turn it on and see what happens?


| 
| Another tack, as a temporary workaround:  try disabling optimization only
| for Objects/floatobject.c.  That will probably fix the problem, and if so
| that's enough of a workaround to get you unstuck while pursuing these other
| irritations.

this one works just fine.  workarounds aren't a problem for me right
now since I'm in no hurry to get this version in use here.  I'm just
trying to help debug this version for irix users in general.


------------%< snip %<----------------------%< snip %<------------

(tommy@mace)/u0/tommy/pycvs/python/dist/src$ dbx python
dbx version 7.3 65959_Jul11 patchSG0003841 Jul 11 2000 02:29:30
Executable /usr/u0/tommy/pycvs/python/dist/src/python
(dbx) run
Process 563746 (python) started
Python 2.1a2 (#6, Feb 13 2001, 17:43:32) [C] on irix6
Type "copyright", "credits" or "license" for more information.
>>> 3 * 4.0
12.0
>>> import math
>>> 4 * math.exp(-.5)
Process 563746 (python) stopped on signal SIGBUS: Bus error (default) at [float_mul:383 +0x4,0x1004c158]
 383  CONVERT_TO_DOUBLE(v, a);
(dbx) l
>* 383          CONVERT_TO_DOUBLE(v, a);
   384          CONVERT_TO_DOUBLE(w, b);
   385          PyFPE_START_PROTECT("multiply", return 0)
   386          a = a * b;
   387          PyFPE_END_PROTECT(a)
   388          return PyFloat_FromDouble(a);
   389  }
   390  
   391  static PyObject *
   392  float_div(PyObject *v, PyObject *w)
(dbx) t
>  0 float_mul(0x100b69fc, 0x10116788, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Objects/floatobject.c":383, 0x1004c158]
   1 binary_op1(0x100b69fc, 0x10116788, 0x0, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Objects/abstract.c":337, 0x1003ac5c]
   2 binary_op(0x100b69fc, 0x10116788, 0x8, 0x0, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Objects/abstract.c":373, 0x1003ae70]
   3 PyNumber_Multiply(0x100b69fc, 0x10116788, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Objects/abstract.c":544, 0x1003b5a4]
   4 eval_code2(0x1012c688, 0x0, 0xffffffec, 0x0, 0x0, 0x0, 0x0, 0x0) ["/usr/u0/tommy/pycvs/python/dist/src/Python/ceval.c":896, 0x10034a54]
   5 PyEval_EvalCode(0x100b69fc, 0x10116788, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Python/ceval.c":336, 0x10031768]
   6 run_node(0x100f88c0, 0x10116788, 0x0, 0x0, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Python/pythonrun.c":931, 0x10040444]
   7 PyRun_InteractiveOne(0x0, 0x100b1878, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Python/pythonrun.c":540, 0x1003f1f0]
   8 PyRun_InteractiveLoop(0xfb4a398, 0x100b1878, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Python/pythonrun.c":486, 0x1003ef84]
   9 PyRun_AnyFileEx(0xfb4a398, 0x100b1878, 0x0, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Python/pythonrun.c":461, 0x1003eeac]
   10 Py_Main(0x1, 0x0, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Modules/main.c":292, 0x1000bba4]
   11 main(0x100b69fc, 0x10116788, 0x8, 0x100a1318, 0x10050000, 0x10116788, 0x100a1318, 0x100a1290) ["/usr/u0/tommy/pycvs/python/dist/src/Modules/python.c":10, 0x1000b7bc]
More (n if no)?y
   12 __start() ["/xlv55/kudzu-apr12/work/irix/lib/libc/libc_n32_M4/csu/crt1text.s":177, 0x1000b558]
(dbx)