Hello,
With the following code:
test.pyx
--------
cdef extern from "foo.h":
void foo() nogil except +
def bar():
with nogil:
foo()
foo.c
-----
void foo()
{
throw std::runtime_error("foo exception");
}
The following crashes:
python -c "import test; test.bar()"
Dumping at the code of bar() generated by Cython:
{ PyThreadState *_save;
Py_UNBLOCK_THREADS
/*try:*/ {
try {foo();} catch(...) {__Pyx_CppExn2PyErr(); {__pyx_filename =
__pyx_f[0]; __pyx_lineno = 6; __pyx_clineno = __LINE__; goto __pyx_L6;}}
}
/*finally:*/ {
int __pyx_why;
__pyx_why = 0; goto __pyx_L7;
__pyx_L6: __pyx_why = 4; goto __pyx_L7;
__pyx_L7:;
Py_BLOCK_THREADS
switch (__pyx_why) {
case 4: goto __pyx_L1_error;
}
}
}
The problem is that __Pyx_CppExn2PyErr() accesses Python without the GIL.
There are several ways of fixing this.
1/ The simplest, but not the most optimized one: acquire/release the GIL within
__Pyx_CppExn2PyErr().
2/ acquire/release the GIL in the catch clause only when "with nogil":
try {foo();} catch(...) {PyGILState_STATE state = PyGILState_Ensure();
__Pyx_CppExn2PyErr(); PyGILState_Release(state); {__pyx_filename = __pyx_f[0];
__pyx_lineno = 6; __pyx_clineno = __LINE__; goto __pyx_L6;}}
3/ restore the thread in the catch clause:
try {foo();} catch(...) { Py_BLOCK_THREADS __Pyx_CppExn2PyErr();
{__pyx_filename = __pyx_f[0]; __pyx_lineno = 6; __pyx_clineno = __LINE__; goto
__pyx_L6;}}
}
/*finally:*/ {
int __pyx_why;
Py_BLOCK_THREADS // <<<<<<<<<<<<<<<<
__pyx_why = 0; goto __pyx_L7;
__pyx_L6: __pyx_why = 4; goto __pyx_L7;
__pyx_L7:;
switch (__pyx_why) {
case 4: goto __pyx_L1_error;
}
}
}
Cheers,
Stephane
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