[LLVMdev] [cfe-dev] lsan for LLVM bootstrap; leaks in TableGen

[Kostya Serebryany]

Like this?

+extern "C" {
+// Disable LeakSanitizer, see http://llvm.org/bugs/show_bug.cgi?id=18325.
+int __lsan_is_turned_off() { return 1; }
+}  // extern "C"



On Thu, Dec 26, 2013 at 8:53 AM, Chandler Carruth <chandlerc at google.com>wrote:

> LGTM.
>
> I think it is totally reasonable to just disable LSan directly in tablegen
> at least for now.
>
> I would leave some comments on the disabling to clarify:
> 1) What it does, the reader may not have heard about LSan.
> 2) Some of the high-level information from this thread as pointers for
> anyone who wants to go and fix this some day.
>
> -Chandler
>
>
> On Wed, Dec 25, 2013 at 2:26 PM, Kostya Serebryany <kcc at google.com> wrote:
>
>>
>>
>>
>> On Wed, Dec 25, 2013 at 11:21 PM, Alexey Samsonov <samsonov at google.com>wrote:
>>
>>> On Wed, Dec 25, 2013 at 9:38 PM, dblaikie at gmail.com <dblaikie at gmail.com>
>>> wrote:
>>> > Its generally been by design that tblgen leaks. Might be nice to fix
>>> one day
>>> > but it's been that way for a while now so don't expect it to be fixed
>>> soon.
>>> >
>>> > If thats the suppression mechanism of choice (I would've expected a
>>> build
>>> > flag option) for lsan, I'd say go for it.
>>> >
>>> > (Maybe there's some existing build flag handling for valgrind so as
>>> not to
>>> > leak check tblgen, but that would be a runtime flag, not build time)
>>> >
>>> > On Wednesday, December 25, 2013 7:08:27 AM, Kostya Serebryany
>>> > <kcc at google.com> wrote:
>>> >
>>> > Hi,
>>> >
>>> > We are trying to enable LeakSanitizer on our asan/msan llvm bootstrap
>>> bot
>>> >
>>> > (http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/).
>>> >
>>> > In clang itself there are two leaks
>>> >
>>> > (http://llvm.org/bugs/show_bug.cgi?id=18318,
>>> > http://llvm-reviews.chandlerc.com/D2472)
>>> >
>>> > and one lsan-hostile feature (
>>> http://llvm.org/bugs/show_bug.cgi?id=18320),
>>> >
>>> > all of which are easy to fix.
>>> >
>>> > And there are also lots of leaks in TableGen.
>>>
>>> I think the problem with TableGen is that we call leak checking too
>>> late - after the global destructors,
>>> not before them. IIRC pointers to objects "leaked" in TableGen are
>>> stored in a set with static storage duration.
>>> If we're able to call __lsan_do_leak_check() right after main(), we
>>> will treat that objects as reachable.
>>>
>>
>> This is part of the problem. Indeed, there is code like this:
>>
>> void foo() {
>>   static Pool ThePool;
>>    ...
>>   ThePool.Insert(new Stuff);
>>   ...
>> }
>>
>> This static variable is destructed w/o deleting the contents and lsan
>> complains.
>> I've replaced some of these objects with
>>   static Pool *ThePool = new Pool
>> and those leaks were gone.
>>
>> But then there were a few other leaks of different nature, all of which I
>> did not want to investigate.
>>
>>  --kcc
>>
>>
>>
>>> I considered adding a call to __lsan_do_leak_check into
>>> llvm_shutdown() function, but that looks wrong -
>>> for instance, llvm_shutdown() may be called when a dynamic library is
>>> unloaded.
>>>
>>
>>
>>
>>>
>>> >
>>> > Would anyone be interested in fixing TableGen leaks?
>>> >
>>> > I'd guess not since TableGen is not a user-facing utility, leaks there
>>> are
>>> > not too harmful.
>>> >
>>> > If so, I'd like to disable lsan for TableGen so that
>>> >
>>> > we can enable lsan on the bootstrap bot soon. Objections?
>>> >
>>> > --kcc
>>> >
>>> > Index: utils/TableGen/TableGen.cpp
>>> >
>>> > ===================================================================
>>> >
>>> > --- utils/TableGen/TableGen.cpp (revision 198007)
>>> >
>>> > +++ utils/TableGen/TableGen.cpp (working copy)
>>> >
>>> > @@ -180,3 +180,7 @@
>>> >
>>> >
>>> >
>>> >    return TableGenMain(argv[0], &LLVMTableGenMain);
>>> >
>>> >  }
>>> >
>>> > +
>>> >
>>> > +extern "C" {
>>> >
>>> > +int __lsan_is_turned_off() { return 1; }
>>> >
>>> > +}  // extern "C"
>>> >
>>> > Index: tools/clang/utils/TableGen/TableGen.cpp
>>> >
>>> > ===================================================================
>>> >
>>> > --- tools/clang/utils/TableGen/TableGen.cpp     (revision 198007)
>>> >
>>> > +++ tools/clang/utils/TableGen/TableGen.cpp     (working copy)
>>> >
>>> > @@ -248,3 +248,7 @@
>>> >
>>> >
>>> >
>>> >    return TableGenMain(argv[0], &ClangTableGenMain);
>>> >
>>> >  }
>>> >
>>> > +
>>> >
>>> > +extern "C" {
>>> >
>>> > +int __lsan_is_turned_off() { return 1; }
>>> >
>>> > +}  // extern "C"
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > cfe-dev mailing list
>>> > cfe-dev at cs.uiuc.edu
>>> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>> >
>>>
>>>
>>>
>>> --
>>> Alexey Samsonov, MSK
>>>
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>
>>
>
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