bpo-31173: Rewrite WSTOPSIG test of test_subprocess (#3055)

The current test_child_terminated_in_stopped_state() function test
creates a child process which calls ptrace(PTRACE_TRACEME, 0, 0) and
then crash (SIGSEGV). The problem is that calling os.waitpid() in the
parent process is not enough to close the process: the child process
remains alive and so the unit test leaks a child process in a
strange state. Closing the child process requires non-trivial code,
maybe platform specific.

Remove the functional test and replaces it with an unit test which
mocks os.waitpid() using a new _testcapi.W_STOPCODE() function to
test the WIFSTOPPED() path.

1 files changed, 22 insertions, 0 deletions

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 6556690..95c1018 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -18,6 +18,10 @@
 #  include <winsock2.h>         /* struct timeval */
 #endif
 
+#ifdef HAVE_SYS_WAIT_H
+#include <sys/wait.h>           /* For W_STOPCODE */
+#endif
+
 #ifdef WITH_THREAD
 #include "pythread.h"
 #endif /* WITH_THREAD */
@@ -4272,6 +4276,7 @@ test_pyobject_fastcallkeywords(PyObject *self, PyObject *args)
     return _PyObject_FastCallKeywords(func, stack, nargs, kwnames);
 }
 
+
 static PyObject*
 stack_pointer(PyObject *self, PyObject *args)
 {
@@ -4280,6 +4285,20 @@ stack_pointer(PyObject *self, PyObject *args)
 }
 
 
+#ifdef W_STOPCODE
+static PyObject*
+py_w_stopcode(PyObject *self, PyObject *args)
+{
+    int sig, status;
+    if (!PyArg_ParseTuple(args, "i", &sig)) {
+        return NULL;
+    }
+    status = W_STOPCODE(sig);
+    return PyLong_FromLong(status);
+}
+#endif
+
+
 static PyMethodDef TestMethods[] = {
     {"raise_exception",         raise_exception,                 METH_VARARGS},
     {"raise_memoryerror",   (PyCFunction)raise_memoryerror,  METH_NOARGS},
@@ -4493,6 +4512,9 @@ static PyMethodDef TestMethods[] = {
     {"pyobject_fastcalldict", test_pyobject_fastcalldict, METH_VARARGS},
     {"pyobject_fastcallkeywords", test_pyobject_fastcallkeywords, METH_VARARGS},
     {"stack_pointer", stack_pointer, METH_NOARGS},
+#ifdef W_STOPCODE
+    {"W_STOPCODE", py_w_stopcode, METH_VARARGS},
+#endif
     {NULL, NULL} /* sentinel */
 };