Add drgn_error_catch() - take 2 #456
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Looks good to me conceptually, although there's a build error (which apparently makes the CI action get stuck. Oops.) |
brenns10
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How embarrassing, I swear I built and ran this, but I must not have had the |
osandov
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Dec 18, 2024
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Nope, I don't need a public API (we don't currently even release |
Catching errors is a relatively common practice. But to do it correctly,
users should actually look at the error code and may need to use
drgn_error_destroy(). For some kinds of errors, (e.g. lookup errors,
which commonly use &drgn_not_found), it feels more convenient to
directly compare error pointers, but that may leave some errors
unhandled.
Introduce drgn_error_catch(), which makes it more convenient to catch
errors correctly. Its intended use is to convert constructs like (1)
and (2) below, to (3):
// (1)
err = some_function();
if (err->code == DRGN_ERROR_LOOKUP) {
drgn_error_destroy(err);
err = NULL;
// do something else
}
// (2)
err = some_function();
if (err == &drgn_not_found) {
err = NULL;
// do something else
}
// (3)
err = some_function();
if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
// do something else
}
Signed-off-by: Stephen Brennan <[email protected]>
As an example of the functionality, refactor the lookup error handling here to use drgn_error_catch(). Signed-off-by: Stephen Brennan <[email protected]>
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I had opened a PR a while back for a new static inline,
drgn_error_catch(), that makes it easier to catch all errors of a specific code, and destroy them. I tried to convert a bunch of users in that PR which made it go stale super quick. I don't really think that it's necessary to convert a bunch all in one go. So this PR just adds the helper, and does an example conversion inlibdrgn/linux_kernel_helpers.c. That ensures that we can see how it's used and catch any errors, but it also won't conflict with the module API branch (I double-checked), and shouldn't go stale so quickly.I think this would be a nice thing to have in general. It's also related to some of the preparatory commits I have for the CTF branch, and I figured it would be nice to keep closer to upstream by adding this now.