Re: [libvirt-python PATCH 18/23] improve usage of cleanup paths

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On 09/24/2015 10:01 AM, Pavel Hrdina wrote:
> This removes several code duplicates and also some unusual code structures.
> 
> Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
> ---
>  libvirt-override.c | 159 +++++++++++++++++++++++------------------------------
>  1 file changed, 68 insertions(+), 91 deletions(-)
> 
> diff --git a/libvirt-override.c b/libvirt-override.c
> index 8afe7d7..205f0dd 100644
> --- a/libvirt-override.c
> +++ b/libvirt-override.c
> @@ -439,13 +439,13 @@ libvirt_virDomainGetSchedulerType(PyObject *self ATTRIBUTE_UNUSED,
>          return VIR_PY_NONE;
>  
>      /* convert to a Python tuple of long objects */
> -    if ((info = PyTuple_New(2)) == NULL) {
> -        VIR_FREE(c_retval);
> -        return NULL;
> -    }
> +    if ((info = PyTuple_New(2)) == NULL)
> +        goto cleanup;
>  
>      PyTuple_SetItem(info, 0, libvirt_constcharPtrWrap(c_retval));
>      PyTuple_SetItem(info, 1, libvirt_intWrap((long)nparams));
> +
> + cleanup:
>      VIR_FREE(c_retval);
>      return info;
>  }
> @@ -2401,7 +2401,6 @@ libvirt_virDomainSnapshotListNames(PyObject *self ATTRIBUTE_UNUSED,
>              Py_CLEAR(py_retval);
>              goto cleanup;
>          }
> -        VIR_FREE(names[i]);
>      }
>  
>   cleanup:
> @@ -3245,8 +3244,8 @@ libvirt_virNodeGetCellsFreeMemory(PyObject *self ATTRIBUTE_UNUSED,
>      LIBVIRT_END_ALLOW_THREADS;
>  
>      if (c_retval < 0) {
> -        VIR_FREE(freeMems);
> -        return VIR_PY_NONE;
> +        py_retval = VIR_PY_NONE;
> +        goto cleanup;
>      }
>  
>      if ((py_retval = PyList_New(c_retval)) == NULL)
> @@ -3425,24 +3424,19 @@ libvirt_virConnectListStoragePools(PyObject *self ATTRIBUTE_UNUSED,
>              return VIR_PY_NONE;
>          }
>      }
> -    py_retval = PyList_New(c_retval);
> -    if (py_retval == NULL) {
> -        if (names) {
> -            for (i = 0; i < c_retval; i++)
> -                VIR_FREE(names[i]);
> -            VIR_FREE(names);
> -        }
> -        return NULL;
> -    }
> +
> +    if ((py_retval = PyList_New(c_retval)) == NULL)
> +        goto cleanup;
>  
>      if (names) {
> -        for (i = 0; i < c_retval; i++) {
> +        for (i = 0; i < c_retval; i++)
>              PyList_SetItem(py_retval, i, libvirt_constcharPtrWrap(names[i]));
> -            VIR_FREE(names[i]);
> -        }
> -        VIR_FREE(names);
>      }
>  
> + cleanup:
> +    for (i = 0; i < c_retval; i++)
> +        VIR_FREE(names[i]);
> +    VIR_FREE(names);
>      return py_retval;
>  }
>  
> @@ -3480,24 +3474,20 @@ libvirt_virConnectListDefinedStoragePools(PyObject *self ATTRIBUTE_UNUSED,
>              return VIR_PY_NONE;
>          }
>      }
> -    py_retval = PyList_New(c_retval);
> -    if (py_retval == NULL) {
> -        if (names) {
> -            for (i = 0; i < c_retval; i++)
> -                VIR_FREE(names[i]);
> -            VIR_FREE(names);
> -        }
> -        return NULL;
> -    }
> +
> +    if ((py_retval = PyList_New(c_retval)) == NULL)
> +        goto cleanup;
>  
>      if (names) {
> -        for (i = 0; i < c_retval; i++) {
> +        for (i = 0; i < c_retval; i++)
>              PyList_SetItem(py_retval, i, libvirt_constcharPtrWrap(names[i]));
> -            VIR_FREE(names[i]);
> -        }
> -        VIR_FREE(names);
>      }
>  
> + cleanup:
> +    for (i = 0; i < c_retval; i++)
> +        VIR_FREE(names[i]);
> +    VIR_FREE(names);
> +
>      return py_retval;
>  }
>  
> @@ -3579,28 +3569,24 @@ libvirt_virStoragePoolListVolumes(PyObject *self ATTRIBUTE_UNUSED,
>          c_retval = virStoragePoolListVolumes(pool, names, c_retval);
>          LIBVIRT_END_ALLOW_THREADS;
>          if (c_retval < 0) {
> -            VIR_FREE(names);
> -            return VIR_PY_NONE;
> +            py_retval = VIR_PY_NONE;
> +            goto cleanup;

We're going to cleanup with c_retval == -1, right... and then doing the
for loop to free names - could be a long time to complete.

I do note that this differs from other prior uses in this patch - that
is other functions will keep the VIR_FREE(names); return VIR_PY_NONE; if
c_retval < 0

At this point it may be worthwhile for you to check *all* such goto's
for c_retval && loops to free memory...

>          }
>      }
> -    py_retval = PyList_New(c_retval);
> -    if (py_retval == NULL) {
> -        if (names) {
> -            for (i = 0; i < c_retval; i++)
> -                VIR_FREE(names[i]);
> -            VIR_FREE(names);
> -        }
> -        return NULL;
> -    }
> +
> +    if ((py_retval = PyList_New(c_retval)) == NULL)
> +        goto cleanup;
>  
>      if (names) {
> -        for (i = 0; i < c_retval; i++) {
> +        for (i = 0; i < c_retval; i++)
>              PyList_SetItem(py_retval, i, libvirt_constcharPtrWrap(names[i]));
> -            VIR_FREE(names[i]);
> -        }
> -        VIR_FREE(names);
>      }
>  
> + cleanup:
> +    for (i = 0; i < c_retval; i++)
> +        VIR_FREE(names[i]);
> +    VIR_FREE(names);
> +
>      return py_retval;
>  }
>  
> @@ -3850,9 +3836,10 @@ libvirt_virNodeListDevices(PyObject *self ATTRIBUTE_UNUSED,
>          LIBVIRT_BEGIN_ALLOW_THREADS;
>          c_retval = virNodeListDevices(conn, cap, names, c_retval, flags);
>          LIBVIRT_END_ALLOW_THREADS;
> +
>          if (c_retval < 0) {
> -            VIR_FREE(names);
> -            return VIR_PY_NONE;
> +            py_retval = VIR_PY_NONE;
> +            goto cleanup;

oh - look at that... here's a similar comment regarding c_retval as above.

>          }
>      }
>  
> @@ -3947,8 +3934,8 @@ libvirt_virNodeDeviceListCaps(PyObject *self ATTRIBUTE_UNUSED,
>          c_retval = virNodeDeviceListCaps(dev, names, c_retval);
>          LIBVIRT_END_ALLOW_THREADS;
>          if (c_retval < 0) {
> -            VIR_FREE(names);
> -            return VIR_PY_NONE;
> +            py_retval = VIR_PY_NONE;
> +            goto cleanup;

again

>          }
>      }
>  
> @@ -4072,8 +4059,8 @@ libvirt_virConnectListSecrets(PyObject *self ATTRIBUTE_UNUSED,
>          c_retval = virConnectListSecrets(conn, uuids, c_retval);
>          LIBVIRT_END_ALLOW_THREADS;
>          if (c_retval < 0) {
> -            VIR_FREE(uuids);
> -            return VIR_PY_NONE;
> +            py_retval = VIR_PY_NONE;
> +            goto cleanup;

again

>          }
>      }
>  
> @@ -4404,24 +4391,19 @@ libvirt_virConnectListInterfaces(PyObject *self ATTRIBUTE_UNUSED,
>              return VIR_PY_NONE;
>          }
>      }

This one doesn't...

> -    py_retval = PyList_New(c_retval);
> -    if (py_retval == NULL) {
> -        if (names) {
> -            for (i = 0; i < c_retval; i++)
> -                VIR_FREE(names[i]);
> -            VIR_FREE(names);
> -        }
> -        return NULL;
> -    }
> +
> +    if ((py_retval = PyList_New(c_retval)) == NULL)
> +        goto cleanup;
>  
>      if (names) {
> -        for (i = 0; i < c_retval; i++) {
> +        for (i = 0; i < c_retval; i++)
>              PyList_SetItem(py_retval, i, libvirt_constcharPtrWrap(names[i]));
> -            VIR_FREE(names[i]);
> -        }
> -        VIR_FREE(names);
>      }
>  
> + cleanup:
> +    for (i = 0; i < c_retval; i++)
> +        VIR_FREE(names[i]);
> +    VIR_FREE(names);
>      return py_retval;
>  }
>  
> @@ -4461,24 +4443,19 @@ libvirt_virConnectListDefinedInterfaces(PyObject *self ATTRIBUTE_UNUSED,
>              return VIR_PY_NONE;
>          }
>      }
> -    py_retval = PyList_New(c_retval);
> -    if (py_retval == NULL) {
> -        if (names) {
> -            for (i = 0; i < c_retval; i++)
> -                VIR_FREE(names[i]);
> -            VIR_FREE(names);
> -        }
> -        return NULL;
> -    }
> +
> +    if ((py_retval = PyList_New(c_retval)) == NULL)
> +        goto cleanup;
>  
>      if (names) {
> -        for (i = 0; i < c_retval; i++) {
> +        for (i = 0; i < c_retval; i++)
>              PyList_SetItem(py_retval, i, libvirt_constcharPtrWrap(names[i]));
> -            VIR_FREE(names[i]);
> -        }
> -        VIR_FREE(names);
>      }
>  
> + cleanup:
> +    for (i = 0; i < c_retval; i++)
> +        VIR_FREE(names[i]);
> +    VIR_FREE(names);
>      return py_retval;
>  }
>  
> @@ -8459,17 +8436,19 @@ libvirt_virDomainGetFSInfo(PyObject *self ATTRIBUTE_UNUSED,
>  
>      /* convert to a Python list */
>      if ((py_retval = PyList_New(c_retval)) == NULL)
> -        goto cleanup;
> +        goto error;
>  
>      for (i = 0; i < c_retval; i++) {
>          virDomainFSInfoPtr fs = fsinfo[i];
>          PyObject *info, *alias;
>  
>          if (fs == NULL)
> -            goto cleanup;
> +            goto error;
> +
>          info = PyTuple_New(4);
>          if (info == NULL)
> -            goto cleanup;
> +            goto error;
> +
>          PyList_SetItem(py_retval, i, info);
>  
>          PyTuple_SetItem(info, 0, libvirt_constcharPtrWrap(fs->mountpoint));
> @@ -8478,27 +8457,25 @@ libvirt_virDomainGetFSInfo(PyObject *self ATTRIBUTE_UNUSED,
>  
>          alias = PyList_New(0);
>          if (alias == NULL)
> -            goto cleanup;
> +            goto error;
>  
>          PyTuple_SetItem(info, 3, alias);
>  
>          for (j = 0; j < fs->ndevAlias; j++)
>              if (PyList_Append(alias,
>                                libvirt_constcharPtrWrap(fs->devAlias[j])) < 0)
> -                goto cleanup;
> +                goto error;
>      }
>  

Perhaps this one was pre-existing, but if c_retval < 0, this isn't going
to go well... or it won't be quick!


John
> + cleanup:
>      for (i = 0; i < c_retval; i++)
>          virDomainFSInfoFree(fsinfo[i]);
>      VIR_FREE(fsinfo);
>      return py_retval;
>  
> - cleanup:
> -    for (i = 0; i < c_retval; i++)
> -        virDomainFSInfoFree(fsinfo[i]);
> -    VIR_FREE(fsinfo);
> -    Py_XDECREF(py_retval);
> -    return NULL;
> + error:
> +    Py_CLEAR(py_retval);
> +    goto cleanup;
>  }
>  
>  #endif /* LIBVIR_CHECK_VERSION(1, 2, 11) */
> 

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