libvirt-utils: Clear error when guessing typed param typev8.6.0

Our APIs which accept typed parameters are usually exposed in
python as accepting dictionary, for instance:

  virDomainSetIOThreadParams(..., virTypedParameterPtr params, ...) ->
  virDomain.setIOThreadParams(..., {}, ...)

Now, before calling the C API, the dictionary is processed by
virPyDictToTypedParams() which accepts an additional argument:
array that hints types for each typed parameter. However, if a
key is not in the array we guess what the correct type might be.
This is done by attempting conversion from python into string, if
that fails then into boolean, then into long, only to fall back
to double. Now, for the long type we can have two cases: the
value is non-negative (ULL) or it is negative (LL). Therefore, we
firstly attempt ULL case and if that fails we stick with the
latter.

However, after we attempted the ULL conversion, python records an
error internally (which is then queried via PyErr_Occurred()),
but the error is never cleared out. This leads to spurious paths
taken afterwards: e.g. when libvirt_longlongUnwrap() is trying to
convert -1, it fails. But not rightfully - the PyErr_Occurred()
check it performs has nothing to do with any of its actions,
rather than our guessing work done before.

Therefore, clear the error after we've guessed the type.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/libvirt-utils.c b/libvirt-utils.c
index d8ff11d..a964779 100644
--- a/libvirt-utils.c
+++ b/libvirt-utils.c
@@ -408,10 +408,12 @@ virPyDictToTypedParamOne(virTypedParameterPtr *params,
             type = VIR_TYPED_PARAM_BOOLEAN;
         } else if (PyLong_Check(value)) {
             unsigned long long ull = PyLong_AsUnsignedLongLong(value);
-            if (ull == (unsigned long long) -1 && PyErr_Occurred())
+            if (ull == (unsigned long long) -1 && PyErr_Occurred()) {
                 type = VIR_TYPED_PARAM_LLONG;
-            else
+                PyErr_Clear();
+            } else {
                 type = VIR_TYPED_PARAM_ULLONG;
+            }
         } else if (PyFloat_Check(value)) {
             type = VIR_TYPED_PARAM_DOUBLE;
         }