1:27 p.m.
Following Eric's suggestions from v2, this adds .string, .errno and
.__str__ properties. The .string property returns the error string.
The .errno property returns the errno (from the errno module), or
None. The __str__ property makes the exception nicely printable.
Rich.
1:27 p.m.
Previously errors caused a RuntimeException to be raised. This commit
defines a custom exception (nbd.Error) which has two parameters, the
required error string, and the optional errno (which may be 0 if
unavailable).
For example:
$ ./run nbdsh -c 'h.pread(0, 0)'
Traceback (most recent call last):
File "/usr/lib64/python3.7/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/usr/lib64/python3.7/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/home/rjones/d/libnbd/python/nbd.py", line 1163, in <module>
nbdsh.shell()
File "/home/rjones/d/libnbd/python/nbdsh.py", line 62, in shell
exec (c)
File "<string>", line 1, in <module>
File "/home/rjones/d/libnbd/python/nbd.py", line 483, in pread
return libnbdmod.pread (self._o, count, offset, flags)
nbd.Error: nbd_pread: invalid state: START: the handle must be connected and finished
handshaking with the server: Transport endpoint is not connected (ENOTCONN)
---
generator/generator | 53 ++++++++++++++++++++++++++++++++++++++-
python/t/610-exception.py | 32 +++++++++++++++++++++++
2 files changed, 84 insertions(+), 1 deletion(-)
diff --git a/generator/generator b/generator/generator
index 157a9cb..7c2fb59 100755
--- a/generator/generator
+++ b/generator/generator
@@ -3337,6 +3337,19 @@ get_handle (PyObject *obj)
return (struct nbd_handle *) PyCapsule_GetPointer(obj, \"nbd_handle\");
}
+/* nbd.Error exception. */
+extern PyObject *nbd_internal_py_Error;
+
+static inline void
+raise_exception ()
+{
+ PyObject *args = PyTuple_New (2);
+
+ PyTuple_SetItem (args, 0, PyUnicode_FromString (nbd_get_error ()));
+ PyTuple_SetItem (args, 1, PyLong_FromLong (nbd_get_errno ()));
+ PyErr_SetObject (nbd_internal_py_Error, args);
+}
+
";
List.iter (
@@ -3390,6 +3403,9 @@ static struct PyModuleDef moduledef = {
NULL, /* m_free */
};
+/* nbd.Error exception. */
+PyObject *nbd_internal_py_Error;
+
extern PyMODINIT_FUNC PyInit_libnbdmod (void);
PyMODINIT_FUNC
@@ -3401,6 +3417,11 @@ PyInit_libnbdmod (void)
if (mod == NULL)
return NULL;
+ nbd_internal_py_Error = PyErr_NewException (\"nbd.Error\", NULL, NULL);
+ if (nbd_internal_py_Error == NULL)
+ return NULL;
+ PyModule_AddObject (mod, \"Error\", nbd_internal_py_Error);
+
return mod;
}
"
@@ -3796,7 +3817,7 @@ let print_python_binding name { args; ret } =
| RBool | RErr | RFd | RInt | RInt64 -> pr " if (ret == -1) {\n";
| RConstString | RString -> pr " if (ret == NULL) {\n";
);
- pr " PyErr_SetString (PyExc_RuntimeError, nbd_get_error ());\n";
+ pr " raise_exception ();\n";
pr " py_ret = NULL;\n";
pr " goto out;\n";
pr " }\n";
@@ -3917,6 +3938,36 @@ Read the libnbd(3) man page to find out how to use the API.
import libnbdmod
+# Re-export Error exception as nbd.Error, adding some methods.
+from libnbdmod import Error
+
+Error.__doc__ = '''
+Exception thrown when the underlying libnbd call fails.
+
+This exception has two properties to query the error. Use
+the .string property to return a printable string containing
+the error message. Use the .errno property to return a
+Python errno (which may be None in some cases if the error
+did not correspond to a system call failure).
+'''
+
+Error.string = property (lambda self: self.args[0])
+
+def _errno (self):
+ import errno
+ try:
+ return errno.errorcode[self.args[1]]
+ except KeyError:
+ return None
+Error.errno = property (_errno)
+
+def _str (self):
+ if self.errno:
+ return (\"%%s (%%s)\" %% (self.string, self.errno))
+ else:
+ return (\"%%s\" %% self.string)
+Error.__str__ = _str
+
";
List.iter (fun (n, i) -> pr "%-30s = %d\n" n i) constants;
diff --git a/python/t/610-exception.py b/python/t/610-exception.py
new file mode 100644
index 0000000..847dfac
--- /dev/null
+++ b/python/t/610-exception.py
@@ -0,0 +1,32 @@
+# libnbd Python bindings
+# Copyright (C) 2010-2019 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+import nbd
+
+h = nbd.NBD ()
+
+try:
+ # This will always throw an exception because the handle is not
+ # connected.
+ h.pread (0, 0)
+except nbd.Error as ex:
+ print ("string = %s" % ex.string)
+ print ("errno = %s" % ex.errno)
+ exit (0)
+
+# If we reach here then we didn't catch the exception above.
+exit (1)
--
2.22.0
1:53 p.m.
On 6/28/19 1:27 PM, Richard W.M. Jones wrote:
Previously errors caused a RuntimeException to be raised. This
commit
defines a custom exception (nbd.Error) which has two parameters, the
required error string, and the optional errno (which may be 0 if
unavailable).
For example:
$ ./run nbdsh -c 'h.pread(0, 0)'
Traceback (most recent call last):
File "/usr/lib64/python3.7/runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "/usr/lib64/python3.7/runpy.py", line 85, in _run_code
exec(code, run_globals)
File "/home/rjones/d/libnbd/python/nbd.py", line 1163, in <module>
nbdsh.shell()
File "/home/rjones/d/libnbd/python/nbdsh.py", line 62, in shell
exec (c)
File "<string>", line 1, in <module>
File "/home/rjones/d/libnbd/python/nbd.py", line 483, in pread
return libnbdmod.pread (self._o, count, offset, flags)
nbd.Error: nbd_pread: invalid state: START: the handle must be connected and finished
handshaking with the server: Transport endpoint is not connected (ENOTCONN)
Cool - in the time I spent writing my reply to v2 1/1, your reaction to
my reply on 0/1 figured out the way to get what we want:
@@ -3917,6 +3938,36 @@ Read the libnbd(3) man page to find out how to
use the API.
import libnbdmod
+# Re-export Error exception as nbd.Error, adding some methods.
+from libnbdmod import Error
Implement all the cool stuff in pure Python on top of the bare-bones
minimum :) Lots less hassle than writing it in C code. I like it!
+
+Error.__doc__ = '''
+Exception thrown when the underlying libnbd call fails.
+
+This exception has two properties to query the error. Use
+the .string property to return a printable string containing
+the error message. Use the .errno property to return a
+Python errno (which may be None in some cases if the error
+did not correspond to a system call failure).
+'''
+
+Error.string = property (lambda self: self.args[0])
+
+def _errno (self):
+ import errno
+ try:
+ return errno.errorcode[self.args[1]]
+ except KeyError:
+ return None
+Error.errno = property (_errno)
+
+def _str (self):
+ if self.errno:
+ return (\"%%s (%%s)\" %% (self.string, self.errno))
+ else:
+ return (\"%%s\" %% self.string)
+Error.__str__ = _str
Looks good to me now! Thanks for figuring this out while I was
struggling with reading lots of documentation on C bindings.
ACK
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
2:17 p.m.
On Fri, Jun 28, 2019 at 01:53:11PM -0500, Eric Blake wrote:
On 6/28/19 1:27 PM, Richard W.M. Jones wrote:
> Previously errors caused a RuntimeException to be raised. This commit
> defines a custom exception (nbd.Error) which has two parameters, the
> required error string, and the optional errno (which may be 0 if
> unavailable).
>
> For example:
>
> $ ./run nbdsh -c 'h.pread(0, 0)'
> Traceback (most recent call last):
> File "/usr/lib64/python3.7/runpy.py", line 193, in _run_module_as_main
> "__main__", mod_spec)
> File "/usr/lib64/python3.7/runpy.py", line 85, in _run_code
> exec(code, run_globals)
> File "/home/rjones/d/libnbd/python/nbd.py", line 1163, in
<module>
> nbdsh.shell()
> File "/home/rjones/d/libnbd/python/nbdsh.py", line 62, in shell
> exec (c)
> File "<string>", line 1, in <module>
> File "/home/rjones/d/libnbd/python/nbd.py", line 483, in pread
> return libnbdmod.pread (self._o, count, offset, flags)
> nbd.Error: nbd_pread: invalid state: START: the handle must be connected and
finished handshaking with the server: Transport endpoint is not connected (ENOTCONN)
Cool - in the time I spent writing my reply to v2 1/1, your reaction to
my reply on 0/1 figured out the way to get what we want:
> @@ -3917,6 +3938,36 @@ Read the libnbd(3) man page to find out how to use the API.
>
> import libnbdmod
>
> +# Re-export Error exception as nbd.Error, adding some methods.
> +from libnbdmod import Error
Implement all the cool stuff in pure Python on top of the bare-bones
minimum :) Lots less hassle than writing it in C code. I like it!
> +
> +Error.__doc__ = '''
> +Exception thrown when the underlying libnbd call fails.
> +
> +This exception has two properties to query the error. Use
> +the .string property to return a printable string containing
> +the error message. Use the .errno property to return a
> +Python errno (which may be None in some cases if the error
> +did not correspond to a system call failure).
> +'''
> +
> +Error.string = property (lambda self: self.args[0])
> +
> +def _errno (self):
> + import errno
> + try:
> + return errno.errorcode[self.args[1]]
> + except KeyError:
> + return None
> +Error.errno = property (_errno)
> +
> +def _str (self):
> + if self.errno:
> + return (\"%%s (%%s)\" %% (self.string, self.errno))
> + else:
> + return (\"%%s\" %% self.string)
> +Error.__str__ = _str
Looks good to me now! Thanks for figuring this out while I was
struggling with reading lots of documentation on C bindings.
ACK
I pushed it, but there may be a few issues still:
- Still no error checking in raise_exception(). We're on an error
path already here so it's hard to do anything useful, although
perhaps we should not segfault.
- The .errno attribute returns a (Python module) errno value, not a
number, so the number is effectively lost, should that really be an
issue.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html
2:43 p.m.
On 6/28/19 2:17 PM, Richard W.M. Jones wrote:
>
> Looks good to me now! Thanks for figuring this out while I was
> struggling with reading lots of documentation on C bindings.
>
> ACK
I pushed it, but there may be a few issues still:
- Still no error checking in raise_exception(). We're on an error
path already here so it's hard to do anything useful, although
perhaps we should not segfault.
Yeah, avoiding the segfault is still worthwhile - but our lack of
PyFOO_BAR() error checking is more pervasive than just in
raise_exception(), so a patch to audit all of our generated code will
pick that up along with the rest.
- The .errno attribute returns a (Python module) errno value, not a
number, so the number is effectively lost, should that really be an
issue.
Maybe we want two fields, both .errno (string name, or None if Python
errno.errorcode couldn't map it to a name), and .errnum (raw numeric
value, accessible no matter what).
Maybe as simple as this (or with one further tweak to __str__ to at
least output .errnum when .errno is None):
diff --git i/generator/generator w/generator/generator
index 7c2fb59..9192988 100755
--- i/generator/generator
+++ w/generator/generator
@@ -3944,11 +3944,14 @@ from libnbdmod import Error
Error.__doc__ = '''
Exception thrown when the underlying libnbd call fails.
-This exception has two properties to query the error. Use
+This exception has three properties to query the error. Use
the .string property to return a printable string containing
-the error message. Use the .errno property to return a
-Python errno (which may be None in some cases if the error
-did not correspond to a system call failure).
+the error message. Use the .errnum property for the associated
+numeric error value (which may be 0 if the error did not
+correspond to a system call failure), or the .errno property to
+return a string containing the Python errno name if one is known
+(which may be None if the numeric value does not correspond to
+a known errno name).
'''
Error.string = property (lambda self: self.args[0])
@@ -3961,6 +3964,8 @@ def _errno (self):
return None
Error.errno = property (_errno)
+Error.errnum = property (lambda self: self.args[1])
+
def _str (self):
if self.errno:
return (\"%%s (%%s)\" %% (self.string, self.errno))
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
2:45 p.m.
On Fri, Jun 28, 2019 at 02:43:48PM -0500, Eric Blake wrote:
On 6/28/19 2:17 PM, Richard W.M. Jones wrote:
>>
>> Looks good to me now! Thanks for figuring this out while I was
>> struggling with reading lots of documentation on C bindings.
>>
>> ACK
>
> I pushed it, but there may be a few issues still:
>
> - Still no error checking in raise_exception(). We're on an error
> path already here so it's hard to do anything useful, although
> perhaps we should not segfault.
Yeah, avoiding the segfault is still worthwhile - but our lack of
PyFOO_BAR() error checking is more pervasive than just in
raise_exception(), so a patch to audit all of our generated code will
pick that up along with the rest.
>
> - The .errno attribute returns a (Python module) errno value, not a
> number, so the number is effectively lost, should that really be an
> issue.
Maybe we want two fields, both .errno (string name, or None if Python
errno.errorcode couldn't map it to a name), and .errnum (raw numeric
value, accessible no matter what).
Maybe as simple as this (or with one further tweak to __str__ to at
least output .errnum when .errno is None):
diff --git i/generator/generator w/generator/generator
index 7c2fb59..9192988 100755
--- i/generator/generator
+++ w/generator/generator
@@ -3944,11 +3944,14 @@ from libnbdmod import Error
Error.__doc__ = '''
Exception thrown when the underlying libnbd call fails.
-This exception has two properties to query the error. Use
+This exception has three properties to query the error. Use
the .string property to return a printable string containing
-the error message. Use the .errno property to return a
-Python errno (which may be None in some cases if the error
-did not correspond to a system call failure).
+the error message. Use the .errnum property for the associated
+numeric error value (which may be 0 if the error did not
+correspond to a system call failure), or the .errno property to
+return a string containing the Python errno name if one is known
+(which may be None if the numeric value does not correspond to
+a known errno name).
'''
Error.string = property (lambda self: self.args[0])
@@ -3961,6 +3964,8 @@ def _errno (self):
return None
Error.errno = property (_errno)
+Error.errnum = property (lambda self: self.args[1])
+
def _str (self):
if self.errno:
return (\"%%s (%%s)\" %% (self.string, self.errno))
Yes this works, ACK.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW
3:01 p.m.
On 6/28/19 1:27 PM, Richard W.M. Jones wrote:
Previously errors caused a RuntimeException to be raised. This
commit
defines a custom exception (nbd.Error) which has two parameters, the
required error string, and the optional errno (which may be 0 if
unavailable).
+static inline void
+raise_exception ()
+{
+ PyObject *args = PyTuple_New (2);
+
+ PyTuple_SetItem (args, 0, PyUnicode_FromString (nbd_get_error ()));
+ PyTuple_SetItem (args, 1, PyLong_FromLong (nbd_get_errno ()));
These three lines could probably be compressed into:
Py_BuildValue("si", nbd_get_error(), nbd_get_errno ());
I'll look for other shortcuts like that while auditing for proper error
checking.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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