[Libguestfs] [PATCH libnbd v3] python: Raise a custom exception containing error string and errno.
Eric Blake
eblake at redhat.com
Fri Jun 28 19:43:48 UTC 2019
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
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