[cfe-dev] ASTImporter patches and improvements, please help

Alexey Sidorin via cfe-dev cfe-dev at lists.llvm.org
Sat Dec 1 11:28:21 PST 2018

Hi Gabor,

Thank you for taking care of this issue!
I completely agree with what you said. In my opinion, there are also two 
more things we have to care about.

1. We need to involve LLDB developers into ASTImporter reviews. While we 
are familiar with the ASTImporter usage in CSA, LLDB developers are much 
more familiar with the usage of this component in LLDB so their opinion 
is always appreciated. If there is anybody who can participate in the 
reviews - please let us know.
2. We have to get more familiar with LLDB ourself. The code related to 
the ASTImporter looks pretty well isolated so I think there will be no 
too much problems with it. The build bots breakage already made us take 
a look on the related components.

01.12.2018 19:00, Gábor Márton via cfe-dev пишет:
> Dear LLDB Developers,
> There is an ongoing activity to improve ASTImporter in Clang to make 
> it support
> C++ (and C) completely and correctly.  Our team works on cross 
> translation unit
> (CTU) static analysis where we use the in-tree Clang static analyzer in
> combination with the ASTImporter (via the scan-build.py script or 
> CodeChecker).
> In the past 18 months we have committed more than 70 patches to make the
> ASTImporter better.  Our primary target is Linux and we do run the 
> LLDB tests
> on Linux before we commit.  Unfortunately, quite recently 3 of these 
> patches
> broke the LLDB macOS buildbots (green.lab.llvm.org/green/view/LLDB 
> <http://green.lab.llvm.org/green/view/LLDB>) and this
> caused some turmoil.  We are very sorry about this and we are making 
> actions to
> avoid such inconveniences in the future: We ordered a Mac Mini, until it
> arrives we are using a borrowed Mac Book. We are going to create a CI 
> job which
> will execute the macOS LLDB test suite for a specific patch. Besides 
> this, for
> every patch we are going to monitor the macOS buildbots once they are
> committed.
> However, we are experiencing problems both with the buildbots and with 
> the LLDB
> tests, therefore we are asking help from the LLDB community in the 
> following:
> (1) Apparently, the green lab macOS buildbots are not displayed in the 
> build
> bot console (http://lab.llvm.org:8011/console). More importantly they 
> are not
> capable of sending emails to the authors of the commit in case of failure.
> Would it be possible to setup the these buildbots to send out the 
> emails for
> the authors?
> (2) We are facing difficulties with the LLDB lit tests both on macOS 
> and on
> Linux. E.g. on a fresh macOS mojave install, checking out master LLVM, 
> Clang,
> LLDB and then executing ninja check-lldb fails immediately.  On Linux we
> experienced that some tests fail because they try to read a non-existent
> register. Some tests fail non-deterministically because they can't kill a
> process or a timeout is not long enough. Some tests fail because of a 
> linker
> error of libcxx. We would like to address all these issues. Would you 
> like to
> discuss these issues on lldb-dev or should we create a bugzilla ticket for
> each?
> (3) ASTImporter unit tests and lit tests in Clang for the LLDB 
> specific usage
> are very-very limited.  LLDB uses the so called "minimal" import, but 
> none of
> the unit tests exercises that (CTU uses the full import).  We should 
> have a
> unit test suite where the LLDB use cases are covered, e.g. after a minimal
> import an `importDefinition` is called. Also, a test double which 
> implements
> the ExternalASTSource could be used.  I believe it would be possible 
> to cover
> with the unit tests all LLDB/macOS related scenarios and these tests 
> could run
> on Linux too.  We do something similar in case of windows: we execute 
> all unit
> tests with "-fdelayed-template-parsing" and with "-fms-compatibility" 
> too. I
> think, the more unit tests we have in Clang the sooner we catch the LLDB
> specific importer errors.  I am asking the LLDB community's help here, 
> because
> we lack the domain knowledge in LLDB so we don't know what 
> expectations should
> we write in each unit test cases.  (About lit tests, there is 
> clang-import-test
> but its coverage seems pretty low and I don't know if that really 
> exercises all
> LLDB use cases.)
> I think that from a better ASTImporter the LLDB debugger can benefit 
> too: the
> `expr` command might give better experience by supporting more C++ 
> constructs
> and by giving better diagnostics.
> Thank you,
> Gabor
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