[Lldb-commits] [lldb] r319516 - ClangASTContext::ParseClassTemplateDecl doesn't always succeed.

[Davide Italiano via lldb-commits]

yes, that should work, and we should give it at least a shot :)

On Fri, Dec 1, 2017 at 11:01 AM, Zachary Turner <zturner at google.com> wrote:
> As you said a smaller repro is needed, but I'm imagining a case where we can
> write a file containing some C++ code that uses a template that LLDB doesn't
> understand, compile it with clang to generate some DWARF, and then run
> `lldb-test clang-ast a.out`, where the clang-ast subcommand loads the file,
> builds an AST out of it, and then dumps the contents of the AST into some
> human readable format to stdout.
>
> If clang won't generate this kind of DWARF, we could always use yaml2obj to
> write the dwarf ourselves.
>
> On Fri, Dec 1, 2017 at 10:49 AM Jim Ingham via lldb-commits
> <lldb-commits at lists.llvm.org> wrote:
>>
>> The immediate failure - not checking for NULL from an API that can return
>> NULL - is more the sort of thing you should enforce in code not by testing,
>> either by having the API return some kind of empty object that clients can
>> deal with in a regular way, or by using something like llvm's forced check
>> errors.  You wouldn't want to use an assert here because it will be a while
>> before lldb can claim to handle every kind of template C++ can produce, so
>> you really just want to fail gracefully.  However, this API is used in only
>> one place in lldb, and is really a subroutine for code comprehension and is
>> unlikely to get other uses.  So I'm fine with just checking for null at its
>> one usage site.
>>
>> The failure shows that we don't yet support all template kinds in lldb,
>> and that we don't have enough testing for a wide variety of C++ template
>> types.  Adrian found one instance of this failure, but it is in the Swift
>> compiler so I need to make a smaller repro case first, then add a test for
>> that type.  The longer term plan for this was supposed to be getting lldb &
>> the llvm dwarf parser unified, writing a test harness independent of lldb
>> that you could just cons up and push a wide variety of DWARF at, fuzz test,
>> etc.  That effort seems to have stalled, however.  For the nonce, when we
>> find failures like this, we add them to the lldb testsuite.
>>
>> But the test that we could ingest this one type - once we fix it so we can
>> - wouldn't tickle this failure anyway, so that effort is really orthogonal
>> to this patch.
>>
>> Jim
>>
>>
>> > On Nov 30, 2017, at 9:45 PM, Davide Italiano <dccitaliano at gmail.com>
>> > wrote:
>> >
>> > On Thu, Nov 30, 2017 at 7:41 PM, Jim Ingham via lldb-commits
>> > <lldb-commits at lists.llvm.org> wrote:
>> >> Author: jingham
>> >> Date: Thu Nov 30 19:41:30 2017
>> >> New Revision: 319516
>> >>
>> >> URL: http://llvm.org/viewvc/llvm-project?rev=319516&view=rev
>> >> Log:
>> >> ClangASTContext::ParseClassTemplateDecl doesn't always succeed.
>> >> When it does, it returns a NULL ClassTemplateDecl.  Don't use
>> >> it if it is NULL...
>> >>
>> >> <rdar://problem/35672107>
>> >>
>> >
>> > Is there a way to test this? There should be one.
>> > Not an expert in the ASTContext, so please feel free to correct me if
>> > I'm wrong.
>>
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