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[1.1.2] Demonstrate that C++ exception thrown in one greenlet, can pr…
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…opagate to another greenlet and corrupt memory

Hello up there. While working on Pygolang I've faced the following
problem: a C++ exception thrown in one greenlet, without any try/catch
block on that greenlet, might become propagated and "handled" by
try/catch block established at another greenlet that happened to switch to
the greenlet in question. "Handled" comes in quotes because the program
usually segfaults after that.

I've also observed segfaults before exception reaches user-level
try/catch block - internally in __cxa_throw. Both this issues are likely
of the same origin - due to the fact that C-level stack of a greenlet
does not start from scratch and starts from C-level stack of the program
state when the greenlet is switched to the first time.

We already have one test for C++ exception handling in test_cpp that
@snaury initially added in d9cb12a. However in that test all greenlets
that throw C++ exceptions also put try/catch at the top of their
C-stack.

In the problem, that I describe, and that added test reproduces, there is
no intended top-level try/catch block in C-stack of the greenlet in
question that throws. As the test shows the exception becomes propagated
to switcher's greenlet context and the program then dies with SIGSEGV:

    test_exception_switch_and_throw (greenlet.tests.test_cpp.CPPTests) ... terminate called after throwing an instance of 'exception_t'
    C++ exception unexpectedly caught in g1		<-- NOTE
    FAIL

    ======================================================================
    FAIL: test_exception_switch_and_throw (greenlet.tests.test_cpp.CPPTests)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "/home/kirr/src/tools/py/gevent/greenlet/src/greenlet/tests/test_cpp.py", line 62, in test_exception_switch_and_throw
        (ret, sig, " (core dumped)" if core else ""))
    AssertionError: failed with ret=0 sig=11 (core dumped)

The C-level backtrace from the dumped core is attached in Appendix I. There the
program dies somehow after running the code from _test_extension_cpp.cpp
module. However with the following dirty-patch the situation becomes more clear:

    --- a/src/greenlet/tests/_test_extension_cpp.cpp
    +++ b/src/greenlet/tests/_test_extension_cpp.cpp
    @@ -70,6 +70,7 @@ test_exception_switch(PyObject* self, PyObject* args)
     static PyObject*
     py_test_exception_throw(PyObject* self, PyObject* args)
     {
    +    abort();
         if (!PyArg_ParseTuple(args, ""))
             return NULL;
         p_test_exception_throw(0);

The C-level backtrace of this abort when, run from under g2, shows that g2
C-stack starts from what was there before for first greenlet with try/catch block:

    #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
    python-greenlet#1  0x00007f8be31e9537 in __GI_abort () at abort.c:79
    python-greenlet#2  0x00007f8be3529423 in py_test_exception_throw (self=0x0, args=0x7f8be317f050)
        at src/greenlet/tests/_test_extension_cpp.cpp:73
    python-greenlet#3  0x00005584d0389903 in PyObject_Call (func=0x7f8be2cdd690, arg=<optimized out>, kw=<optimized out>)
        at ../Objects/abstract.c:2544
    python-greenlet#4  0x00007f8be3530d63 in g_initialstub (mark=0x7ffe6d1b1c88) at src/greenlet/greenlet.c:931
    python-greenlet#5  0x00007f8be3530290 in g_switch (target=0x7f8be2cd6230, args=0x7f8be317f050, kwargs=0x0) at src/greenlet/greenlet.c:692
    python-greenlet#6  0x00007f8be35329e2 in PyGreenlet_Switch (g=0x7f8be2cd6230, args=0x7f8be317f050, kwargs=0x0) at src/greenlet/greenlet.c:1806     <- first switch to G2
    python-greenlet#7  0x00007f8be35294da in test_exception_switch_and_do_in_g2 (self=0x0, args=0x7f8be2ce33d0)                                        <- this code runs in G1
        at src/greenlet/tests/_test_extension_cpp.cpp:105
    python-greenlet#8  0x00005584d039de7a in call_function (oparg=<optimized out>, pp_stack=0x7ffe6d1b1e28) at ../Python/ceval.c:4376
    python-greenlet#9  PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
    python-greenlet#10 0x00005584d039c3cc in PyEval_EvalCodeEx (co=0x7f8be2cd9cb0, globals=<optimized out>, locals=<optimized out>,
        args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
        at ../Python/ceval.c:3608
    python-greenlet#11 0x00005584d03b6b9b in function_call (func=func@entry=0x7f8be2cde650, arg=0x7f8be317f050, kw=0x0)
        at ../Objects/funcobject.c:523
    python-greenlet#12 0x00005584d0389903 in PyObject_Call (func=0x7f8be2cde650, arg=<optimized out>, kw=<optimized out>)
        at ../Objects/abstract.c:2544
    python-greenlet#13 0x00007f8be3530d63 in g_initialstub (mark=0x7ffe6d1b20b8) at src/greenlet/greenlet.c:931
    python-greenlet#14 0x00007f8be3530290 in g_switch (target=0x7f8be2cd6410, args=0x7f8be317f050, kwargs=0x0) at src/greenlet/greenlet.c:692
    python-greenlet#15 0x00007f8be3531c4c in green_switch (self=0x7f8be2cd6410, args=0x7f8be317f050, kwargs=0x0) at src/greenlet/greenlet.c:1321       <- switch to G1
    ...

The problem might be worked-around with putting try/catch on C-stack for
every greenlet, but a more proper fix would be to unlink return address
and C-stack-frame of created greenlet from other greenlets completely
(i.e. rewrite first frame of C-stack for created greenlet to return to NULL).

Thanks beforehand,
Kirill

P.S. The problem described at
  python-greenlet#197 (comment) and
  python-greenlet#205 might be related
  to hereby issue (/cc @ThePrez, @kadler, @jamadden).

P.P.S. The test does not fail on master. I see there @jamadden switched
  the codebase to C++ almost completely and there is some explicit
  attempts to save/restore exception state added in
  python-greenlet@87edf955. However
  that exception save/restore is specific to Win32 and the test succeeds
  for me on Linux. I still see the following comment in
  UserGreenlet::inner_bootstrap

    // C++ exceptions cannot propagate to the parent greenlet from
    // here. (TODO: Do we need a catch(...) clause, perhaps on the
    // function itself? ALl we could do is terminate the program.)

    ( https://github.com/python-greenlet/greenlet/blob/3e534d6b/src/greenlet/greenlet.cpp#L1085-L1104 )

  probably this indeed works only by luck, or due to G_NOEXCEPT modifier
  of UserGreenlet::inner_bootstrap upon seeing which __cxa_throw stops
  unwinding C-stack and just calls std::terminate.

--------

Appendix I. C-level backtrace after the test died with SIGSEGV

  #0  0x0000556bdc30d394 in PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3351
  python-greenlet#1  0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a03acb0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#2  0x0000556bdc325b9b in function_call (func=func@entry=0x7f0b8a03f650, arg=0x7f0b8a4e0050, kw=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#3  0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a03f650, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#4  0x00007f0b8a891d63 in g_initialstub (mark=0x7ffc3ef97988) at src/greenlet/greenlet.c:931
  python-greenlet#5  0x00007f0b8a891290 in g_switch (target=0x7f0b8a037410, args=0x7f0b8a4e0050, kwargs=0x0) at src/greenlet/greenlet.c:692
  python-greenlet#6  0x00007f0b8a892c4c in green_switch (self=0x7f0b8a037410, args=0x7f0b8a4e0050, kwargs=0x0) at src/greenlet/greenlet.c:1321
  python-greenlet#7  0x0000556bdc30ce7a in call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef97ac8) at ../Python/ceval.c:4376
  python-greenlet#8  PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#9  0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a03ad30, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#10 0x0000556bdc312953 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef97ca8,
      func=0x7f0b8a03aed0) at ../Python/ceval.c:4471
  python-greenlet#11 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef97ca8) at ../Python/ceval.c:4396
  python-greenlet#12 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#13 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a03ac30, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#14 0x0000556bdc312953 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef97e88,
      func=0x7f0b8a03af50) at ../Python/ceval.c:4471
  python-greenlet#15 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef97e88) at ../Python/ceval.c:4396
  python-greenlet#16 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#17 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a03adb0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#18 0x0000556bdc312953 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef98068,
      func=0x7f0b8a03f250) at ../Python/ceval.c:4471
  python-greenlet#19 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef98068) at ../Python/ceval.c:4396
  python-greenlet#20 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#21 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a04bd30, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a0752a8, defcount=1,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#22 0x0000556bdc325cc2 in function_call (func=0x7f0b8a0771d0, arg=0x7f0b8a3bd5a0, kw=0x7f0b8a042dd0)
      at ../Objects/funcobject.c:523
  python-greenlet#23 0x0000556bdc30fa96 in PyObject_Call (kw=0x7f0b8a042dd0, arg=0x7f0b8a3bd5a0, func=0x7f0b8a0771d0)
      at ../Objects/abstract.c:2544
  python-greenlet#24 ext_do_call (nk=<optimized out>, na=1, flags=<optimized out>, pp_stack=0x7ffc3ef982a0, func=0x7f0b8a0771d0)
      at ../Python/ceval.c:4690
  python-greenlet#25 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3052
  python-greenlet#26 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a04bf30, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#27 0x0000556bdc325b9b in function_call (func=0x7f0b8a0772d0, arg=arg@entry=0x7f0b8a3bd550, kw=kw@entry=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#28 0x0000556bdc33f553 in PyObject_Call (kw=0x0, arg=0x7f0b8a3bd550, func=<optimized out>) at ../Objects/abstract.c:2544
  python-greenlet#29 instancemethod_call (func=<optimized out>, func@entry=0x7f0b8a3c6a00, arg=0x7f0b8a3bd550, kw=0x0)
      at ../Objects/classobject.c:2600
  python-greenlet#30 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a3c6a00, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#31 0x0000556bdc37eff8 in slot_tp_call (self=self@entry=0x7f0b8a03cfd0, args=0x7f0b8a044210, kwds=0x0)
      at ../Objects/typeobject.c:5609
  python-greenlet#32 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a03cfd0, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#33 0x0000556bdc3128dd in do_call (nk=<optimized out>, na=<optimized out>, pp_stack=0x7ffc3ef98798, func=0x7f0b8a03cfd0)
      at ../Python/ceval.c:4593
  python-greenlet#34 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef98798) at ../Python/ceval.c:4398
  python-greenlet#35 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#36 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d530, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a076ee8, defcount=1,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#37 0x0000556bdc325cc2 in function_call (func=0x7f0b8a07f950, arg=0x7f0b8a3bd780, kw=0x7f0b8a042cb0)
      at ../Objects/funcobject.c:523
  python-greenlet#38 0x0000556bdc30fa96 in PyObject_Call (kw=0x7f0b8a042cb0, arg=0x7f0b8a3bd780, func=0x7f0b8a07f950)
      at ../Objects/abstract.c:2544
  python-greenlet#39 ext_do_call (nk=<optimized out>, na=1, flags=<optimized out>, pp_stack=0x7ffc3ef989d0, func=0x7f0b8a07f950)
      at ../Python/ceval.c:4690
  python-greenlet#40 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3052
  python-greenlet#41 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d2b0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#42 0x0000556bdc325b9b in function_call (func=0x7f0b8a07f850, arg=arg@entry=0x7f0b8a3bd730, kw=kw@entry=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#43 0x0000556bdc33f553 in PyObject_Call (kw=0x0, arg=0x7f0b8a3bd730, func=<optimized out>) at ../Objects/abstract.c:2544
  python-greenlet#44 instancemethod_call (func=<optimized out>, func@entry=0x7f0b8a427190, arg=0x7f0b8a3bd730, kw=0x0)
      at ../Objects/classobject.c:2600
  python-greenlet#45 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a427190, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#46 0x0000556bdc37eff8 in slot_tp_call (self=self@entry=0x7f0b8a03cf90, args=0x7f0b8a044150, kwds=0x0)
      at ../Objects/typeobject.c:5609
  python-greenlet#47 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a03cf90, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#48 0x0000556bdc3128dd in do_call (nk=<optimized out>, na=<optimized out>, pp_stack=0x7ffc3ef98ec8, func=0x7f0b8a03cf90)
      at ../Python/ceval.c:4593
  python-greenlet#49 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef98ec8) at ../Python/ceval.c:4398
  python-greenlet#50 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#51 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d530, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a076ee8, defcount=1,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#52 0x0000556bdc325cc2 in function_call (func=0x7f0b8a07f950, arg=0x7f0b8a3bdaf0, kw=0x7f0b8a042b90)
      at ../Objects/funcobject.c:523
  python-greenlet#53 0x0000556bdc30fa96 in PyObject_Call (kw=0x7f0b8a042b90, arg=0x7f0b8a3bdaf0, func=0x7f0b8a07f950)
      at ../Objects/abstract.c:2544
  python-greenlet#54 ext_do_call (nk=<optimized out>, na=1, flags=<optimized out>, pp_stack=0x7ffc3ef99100, func=0x7f0b8a07f950)
      at ../Python/ceval.c:4690
  python-greenlet#55 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3052
  python-greenlet#56 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d2b0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#57 0x0000556bdc325b9b in function_call (func=0x7f0b8a07f850, arg=arg@entry=0x7f0b8a3bdb40, kw=kw@entry=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#58 0x0000556bdc33f553 in PyObject_Call (kw=0x0, arg=0x7f0b8a3bdb40, func=<optimized out>) at ../Objects/abstract.c:2544
  python-greenlet#59 instancemethod_call (func=<optimized out>, func@entry=0x7f0b8a3c6820, arg=0x7f0b8a3bdb40, kw=0x0)
      at ../Objects/classobject.c:2600
  python-greenlet#60 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a3c6820, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#61 0x0000556bdc37eff8 in slot_tp_call (self=self@entry=0x7f0b8a033c50, args=0x7f0b8a03c0d0, kwds=0x0)
      at ../Objects/typeobject.c:5609
  python-greenlet#62 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a033c50, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#63 0x0000556bdc3128dd in do_call (nk=<optimized out>, na=<optimized out>, pp_stack=0x7ffc3ef995f8, func=0x7f0b8a033c50)
      at ../Python/ceval.c:4593
  python-greenlet#64 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef995f8) at ../Python/ceval.c:4398
  python-greenlet#65 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#66 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d530, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a076ee8, defcount=1,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#67 0x0000556bdc325cc2 in function_call (func=0x7f0b8a07f950, arg=0x7f0b8a3bd500, kw=0x7f0b8a042a70)
      at ../Objects/funcobject.c:523
  python-greenlet#68 0x0000556bdc30fa96 in PyObject_Call (kw=0x7f0b8a042a70, arg=0x7f0b8a3bd500, func=0x7f0b8a07f950)
      at ../Objects/abstract.c:2544
  python-greenlet#69 ext_do_call (nk=<optimized out>, na=1, flags=<optimized out>, pp_stack=0x7ffc3ef99830, func=0x7f0b8a07f950)
      at ../Python/ceval.c:4690
  python-greenlet#70 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3052
  python-greenlet#71 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a07d2b0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#72 0x0000556bdc325b9b in function_call (func=0x7f0b8a07f850, arg=arg@entry=0x7f0b8a3bd9b0, kw=kw@entry=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#73 0x0000556bdc33f553 in PyObject_Call (kw=0x0, arg=0x7f0b8a3bd9b0, func=<optimized out>) at ../Objects/abstract.c:2544
  python-greenlet#74 instancemethod_call (func=<optimized out>, func@entry=0x7f0b8a4310a0, arg=0x7f0b8a3bd9b0, kw=0x0)
      at ../Objects/classobject.c:2600
  python-greenlet#75 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a4310a0, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#76 0x0000556bdc37eff8 in slot_tp_call (self=self@entry=0x7f0b8a033c10, args=0x7f0b8a033fd0, kwds=0x0)
      at ../Objects/typeobject.c:5609
  python-greenlet#77 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a033c10, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#78 0x0000556bdc3128dd in do_call (nk=<optimized out>, na=<optimized out>, pp_stack=0x7ffc3ef99d28, func=0x7f0b8a033c10)
      at ../Python/ceval.c:4593
  python-greenlet#79 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef99d28) at ../Python/ceval.c:4398
  python-greenlet#80 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#81 0x0000556bdc3125fe in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef99e38,
      func=0x7f0b8a01ecd0) at ../Python/ceval.c:4461
  python-greenlet#82 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef99e38) at ../Python/ceval.c:4396
  python-greenlet#83 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#84 0x0000556bdc3125fe in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef99f48,
      func=0x7f0b8a01edd0) at ../Python/ceval.c:4461
  python-greenlet#85 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef99f48) at ../Python/ceval.c:4396
  python-greenlet#86 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#87 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a081d30, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=1, defs=0x7f0b8a008ba8, defcount=10,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#88 0x0000556bdc325cc2 in function_call (func=0x7f0b8a00ddd0, arg=arg@entry=0x7f0b8a033610, kw=kw@entry=0x7f0b8a014a70)
      at ../Objects/funcobject.c:523
  python-greenlet#89 0x0000556bdc33f553 in PyObject_Call (kw=0x7f0b8a014a70, arg=0x7f0b8a033610, func=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#90 instancemethod_call (func=<optimized out>, func@entry=0x7f0b8a427140, arg=0x7f0b8a033610, arg@entry=0x7f0b8a4e0050,
      kw=kw@entry=0x7f0b8a014a70) at ../Objects/classobject.c:2600
  python-greenlet#91 0x0000556bdc33f10f in PyObject_Call (kw=0x7f0b8a014a70, arg=0x7f0b8a4e0050, func=0x7f0b8a427140)
      at ../Objects/abstract.c:2544
  python-greenlet#92 slot_tp_init (self=self@entry=0x7f0b8a3ebb10, args=args@entry=0x7f0b8a4e0050, kwds=kwds@entry=0x7f0b8a014a70)
      at ../Objects/typeobject.c:5869
  python-greenlet#93 0x0000556bdc2feb87 in type_call (type=<optimized out>, type@entry=0x556bdd2a85c0, args=0x7f0b8a4e0050, kwds=0x7f0b8a014a70)
      at ../Objects/typeobject.c:765
  python-greenlet#94 0x0000556bdc2f8903 in PyObject_Call (func=0x556bdd2a85c0, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#95 0x0000556bdc3128dd in do_call (nk=<optimized out>, na=<optimized out>, pp_stack=0x7ffc3ef9a458, func=0x556bdd2a85c0)
      at ../Python/ceval.c:4593
  python-greenlet#96 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef9a458) at ../Python/ceval.c:4398
  python-greenlet#97 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#98 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a37d830, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x0, defcount=0, closure=0x0)
      at ../Python/ceval.c:3608
  python-greenlet#99 0x0000556bdc311886 in PyEval_EvalCode (locals=0x7f0b8a4ae170, globals=0x7f0b8a4ae170, co=<optimized out>)
      at ../Python/ceval.c:669
  python-greenlet#100 exec_statement (locals=0x7f0b8a4ae170, globals=0x7f0b8a4ae170, prog=<optimized out>, f=<optimized out>)
      at ../Python/ceval.c:5093
  python-greenlet#101 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:2122
  python-greenlet#102 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a3ea4b0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a381068, defcount=5,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#103 0x0000556bdc312953 in fast_function (nk=<optimized out>, na=<optimized out>, n=<optimized out>, pp_stack=0x7ffc3ef9a818,
      func=0x7f0b8a37d8d0) at ../Python/ceval.c:4471
  python-greenlet#104 call_function (oparg=<optimized out>, pp_stack=0x7ffc3ef9a818) at ../Python/ceval.c:4396
  python-greenlet#105 PyEval_EvalFrameEx (f=<optimized out>, throwflag=<optimized out>) at ../Python/ceval.c:3013
  python-greenlet#106 0x0000556bdc30b3cc in PyEval_EvalCodeEx (co=0x7f0b8a37d4b0, globals=<optimized out>, locals=<optimized out>,
      args=<optimized out>, argcount=<optimized out>, kws=<optimized out>, kwcount=0, defs=0x7f0b8a379ce8, defcount=1,
      closure=0x0) at ../Python/ceval.c:3608
  python-greenlet#107 0x0000556bdc325b9b in function_call (func=func@entry=0x7f0b8a37de50, arg=0x7f0b8a3b5be0, kw=0x0)
      at ../Objects/funcobject.c:523
  python-greenlet#108 0x0000556bdc2f8903 in PyObject_Call (func=0x7f0b8a37de50, arg=<optimized out>, kw=<optimized out>)
      at ../Objects/abstract.c:2544
  python-greenlet#109 0x0000556bdc3b87e1 in RunModule (module=<optimized out>, set_argv0=1) at ../Modules/main.c:197
  python-greenlet#110 0x0000556bdc3a68ed in Py_Main (argc=<optimized out>, argv=<optimized out>) at ../Modules/main.c:592#111 0x00007f0b8a54bd0a in __libc_start_main (main=0x556bdc3a6530 <main>, argc=5, argv=0x7ffc3ef9ac08, init=<optimized out>,
      fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffc3ef9abf8) at ../csu/libc-start.c:308
  python-greenlet#112 0x0000556bdc3a646a in _start ()
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@navytux
navytux committed Jan 10, 2022
1 parent ea9ad9c commit a2985f0
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64 changes: 64 additions & 0 deletions src/greenlet/tests/_test_extension_cpp.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,12 +66,76 @@ test_exception_switch(PyObject* self, PyObject* args)
return p_test_exception_switch_recurse(depth, depth);
}


static PyObject*
py_test_exception_throw(PyObject* self, PyObject* args)
{
if (!PyArg_ParseTuple(args, ""))
return NULL;
p_test_exception_throw(0);
PyErr_SetString(PyExc_AssertionError, "unreachable code running after throw");
return NULL;
}


/* test_exception_switch_and_do_in_g2(g2func)
* - creates new greenlet g2 to run g2func
* - switches to g2 inside try/catch block
* - verifies that no exception has been caught
*
* it is used together with test_exception_throw to verify that unhandled
* exceptions thrown in one greenlet do not propagate to other greenlet nor
* segfault the process.
*/
static PyObject*
test_exception_switch_and_do_in_g2(PyObject* self, PyObject* args)
{
PyObject* g2func = NULL;
PyObject* result = NULL;

if (!PyArg_ParseTuple(args, "O", &g2func))
return NULL;
PyGreenlet* g2 = PyGreenlet_New(g2func, NULL);
if (!g2) {
return NULL;
}

try {
result = PyGreenlet_Switch(g2, NULL, NULL);
if (!result) {
return NULL;
}
}
catch (...) {
/* if we are here the memory can be already corrupted and the program
* might crash before below py-level exception might become printed.
* -> print something to stderr to make it clear that we had entered
* this catch block.
*/
fprintf(stderr, "C++ exception unexpectedly caught in g1\n");
PyErr_SetString(PyExc_AssertionError, "C++ exception unexpectedly caught in g1");
}

Py_XDECREF(result);
Py_RETURN_NONE;
}

static PyMethodDef test_methods[] = {
{"test_exception_switch",
(PyCFunction)&test_exception_switch,
METH_VARARGS,
"Switches to parent twice, to test exception handling and greenlet "
"switching."},
{"test_exception_switch_and_do_in_g2",
(PyCFunction)&test_exception_switch_and_do_in_g2,
METH_VARARGS,
"Creates new greenlet g2 to run g2func and switches to it inside try/catch "
"block. Used together with test_exception_throw to verify that unhandled "
"C++ exceptions thrown in a greenlet doe not corrupt memory."},
{"test_exception_throw",
(PyCFunction)&py_test_exception_throw,
METH_VARARGS,
"Throws C++ exception. Calling this function directly should abort the process."},
{NULL, NULL, 0, NULL}};

#if PY_MAJOR_VERSION >= 3
Expand Down
44 changes: 44 additions & 0 deletions src/greenlet/tests/test_cpp.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,8 @@
from __future__ import absolute_import

import unittest
import os
import signal

import greenlet
from . import _test_extension_cpp
Expand All @@ -16,3 +18,45 @@ def test_exception_switch(self):
greenlets.append(g)
for i, g in enumerate(greenlets):
self.assertEqual(g.switch(), i)

@unittest.skipIf(not hasattr(os, 'fork'),
"test should abort when run -> need to run it in separate process")
def test_exception_switch_and_throw(self):
# procrun runs f in separate process
def procrun(f): # -> (ret, sig, coredumped)
pid = os.fork()

# child
if pid == 0:
f()
os.exit(0)

# parent
_, st = os.waitpid(pid, 0)
ret = st >> 8
sig = st & 0x7f
coredumped = ((st & 0x80) != 0)
return (ret, sig, coredumped)


# verify that plain unhandled throw aborts
# (unhandled throw -> std::terminate -> abort)
ret, sig, _ = procrun(_test_extension_cpp.test_exception_throw)
if not (ret == 0 and sig == signal.SIGABRT):
self.fail("unhandled throw -> ret=%d sig=%d ; expected 0/SIGABRT" % (ret, sig))


# verify that unhandled throw called in greenlet aborts too
# (does not segfaults nor is handled by try/catch on preceeding greenlet C stack)
def _():
def _():
_test_extension_cpp.test_exception_switch_and_do_in_g2(
_test_extension_cpp.test_exception_throw
)
g1 = greenlet.greenlet(_)
g1.switch()

ret, sig, core = procrun(_)
if not (ret == 0 and sig == signal.SIGABRT):
self.fail("failed with ret=%d sig=%d%s" %
(ret, sig, " (core dumped)" if core else ""))

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