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

[Alexey Samsonov]

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.

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"
>
>
>
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-- 
Alexey Samsonov, MSK