[Lldb-commits] [PATCH] D49202: Restructure the minidump loading path and add early & explicit consistency checks

Leonard Mosescu via lldb-commits lldb-commits at lists.llvm.org
Mon Jul 16 10:16:47 PDT 2018

The problem is not returning an error from Minidump::Create() - if that was
the case this could easily be improved indeed. The two-phase initialization
is a consequence of the LLDB plugin lookup:

1. Target::CreateProcess() calls Process::FindPlugin()
2. ProcessMinidump::CreateInstance() then has to inspect the core file to
see if it's a minidump
2b. ... if it is a minidump, we need to create a ProcessMinidump (which
calls MinidumpParser::Create())
3. once the plugin is selected, Process::LoadCore() is finally called and
this the earliest we can do minidump-specific error checking

Note that at step 2b. we don't have a way to propagate the error since
we're just doing the plugin lookup (the most we can pass on the lookup to
the rest of the plugins). We can't easily defer the
MinidumpParser::Create() as step 2b either since that only morphs into a
different kind of two-stage initialization (having a ProcessMinidump w/o a

I agree that it would be nicer with a one step initialization but overall
changing the LLDB plugin lookup is too intrusive for the relatively small
benefit. If you have any suggestions I'd love to hear them.

On Mon, Jul 16, 2018 at 9:04 AM, Pavel Labath via Phabricator <
reviews at reviews.llvm.org> wrote:

> labath added a comment.
> I don't agree with the two-stage initialization of the MinidumpParser
> class being introduced here. We deliberately introduced the `Create` static
> function to avoid this. If this `Initialize` function in checking
> invariants which are assumed to be hold by other parser methods, then it
> should be done by the `Create` function. Ideally this would be done before
> even constructing the parser object, but if this is impractical for some
> reason then you can make the `Initialize` function private and call it
> directly from `Create`. This way a user will never be able to see an
> malformed parser object. To make sure you propagate the error, you can
> change the return type of `Create` to `llvm::Expected<MinidumpParser`
> (the only reason we did not do this back then was that there was no
> precedent for using `Expected` in LLDB, but this is no longer the case).
> Repository:
>   rL LLVM
> https://reviews.llvm.org/D49202
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