[libcxx] r215740 - Revert "Turn off extern templates for most uses."
Eric Fiselier
eric at efcs.ca
Sat Aug 16 02:11:25 PDT 2014
Oh jeez, I forgot a very important aspect to the reproducer. Last time I
looked into this it seemed that __attribute__ ((__always_inline__)) also
played a part in this. In the last example "get_x()" should have this
attribute.
On Sat, Aug 16, 2014 at 3:04 AM, Eric Fiselier <eric at efcs.ca> wrote:
> I could have been a lot clearer. It seems to be a bug in MSAN. I've run
> into it before.
> The code that causes it is something like:
>
> // TestClass.hpp
> template <class T>
> class TestClass
> {
> int x{0};
> int get_x() { return x; }
> };
>
> extern template class TestClass<int>;
>
> // TestClass.cpp
> template class TestClass<int>;
>
> // main.cpp
> #include "TestClass.hpp"
> int main()
> {
> TestClass<int> t;
> // MSAN fires on use of uninitialized value here.
> int x = t.get_x();te
> }
>
> That's by no means a reproducer, but it represents similar code to what
> causes the test failures in "/test/string". MSAN seems to fire *any* time a
> value is returned from a method of a class that has been instantiated
> externally. I think the shared object boundary might be important. I
> haven't had time to investigate.
>
> Unfortunately there is currently no good way to run the libc++ tests with
> sanitizers. The easiest way is to just insert "-fsanitize=memory" into the
> `compile_flags` list in `test/lit.cfg'. Then just "cd test/string ; lit
> -sv . "
>
> I hope that made it a little clearer.
>
> /Eric
>
> P.S. These failures arn't localized to "test/string". They are anywhere
> templates are instantiated externally. String is just representative.
>
>
>
> On Sat, Aug 16, 2014 at 2:42 AM, Justin Bogner <mail at justinbogner.com>
> wrote:
>
>> Eric Fiselier <eric at efcs.ca> writes:
>> > Hi Justin,
>> >
>> > I'm not quite sure we are should do that right now.
>> > If your compiling with MSAN and you call a function in an extern
>> > template MSAN will fire.
>>
>> I don't think I understand what you mean here. Which function? Why does
>> msan fire?
>>
>> > For example testing test/string with MSAN enabled causes 124 failures.
>> > Normally there are just 2.
>>
>> If there are invalid memory accesses we should fix them. I don't see how
>> explicit template instantiations would cause memory errors though.
>>
>> Are there bots that show this issue? How can I reproduce it?
>>
>> > We could probably guard the _LIBCPP_EXTERN_TEMPLATE definition to
>> > check for MSAN but for now I don't think we are ready to re-enable
>> > external template definitions.
>> >
>> > /Eric
>> >
>> > On Fri, Aug 15, 2014 at 11:58 AM, Justin Bogner <mail at justinbogner.com>
>> wrote:
>> >
>> > Author: bogner
>> > Date: Fri Aug 15 12:58:56 2014
>> > New Revision: 215740
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=215740&view=rev
>> > Log:
>> > Revert "Turn off extern templates for most uses."
>> >
>> > Turning off explicit template instantiation leads to a pretty
>> > significant build time and code size cost. We're better off dealing
>> > with ABI incompatibility issues that come up in a less heavy handed
>> > way.
>> >
>> > This reverts commit r189610.
>> >
>> > Modified:
>> > libcxx/trunk/include/__config
>> > libcxx/trunk/src/algorithm.cpp
>> > libcxx/trunk/src/ios.cpp
>> > libcxx/trunk/src/locale.cpp
>> > libcxx/trunk/src/string.cpp
>> > libcxx/trunk/src/valarray.cpp
>> >
>> > Modified: libcxx/trunk/include/__config
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__config?rev
>> > =215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/include/__config (original)
>> > +++ libcxx/trunk/include/__config Fri Aug 15 12:58:56 2014
>> > @@ -608,7 +608,7 @@ template <unsigned> struct __static_asse
>> > #endif
>> >
>> > #ifndef _LIBCPP_EXTERN_TEMPLATE
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...)
>> > +#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > #endif
>> >
>> > #ifndef _LIBCPP_EXTERN_TEMPLATE2
>> >
>> > Modified: libcxx/trunk/src/algorithm.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/algorithm.cpp?
>> > rev=215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/src/algorithm.cpp (original)
>> > +++ libcxx/trunk/src/algorithm.cpp Fri Aug 15 12:58:56 2014
>> > @@ -7,7 +7,6 @@
>> > //
>> > //===
>> >
>> ----------------------------------------------------------------------===/
>> > /
>> >
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > #include "algorithm"
>> > #include "random"
>> > #include "mutex"
>> >
>> > Modified: libcxx/trunk/src/ios.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/ios.cpp?rev=
>> > 215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/src/ios.cpp (original)
>> > +++ libcxx/trunk/src/ios.cpp Fri Aug 15 12:58:56 2014
>> > @@ -7,8 +7,6 @@
>> > //
>> > //===
>> >
>> ----------------------------------------------------------------------===/
>> > /
>> >
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > -
>> > #include "ios"
>> > #include "streambuf"
>> > #include "istream"
>> >
>> > Modified: libcxx/trunk/src/locale.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/locale.cpp?rev=
>> > 215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/src/locale.cpp (original)
>> > +++ libcxx/trunk/src/locale.cpp Fri Aug 15 12:58:56 2014
>> > @@ -7,8 +7,6 @@
>> > //
>> > //===
>> >
>> ----------------------------------------------------------------------===/
>> > /
>> >
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > -
>> > // On Solaris, we need to define something to make the C99 parts of
>> > localeconv
>> > // visible.
>> > #ifdef __sun__
>> >
>> > Modified: libcxx/trunk/src/string.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/string.cpp?rev=
>> > 215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/src/string.cpp (original)
>> > +++ libcxx/trunk/src/string.cpp Fri Aug 15 12:58:56 2014
>> > @@ -7,8 +7,6 @@
>> > //
>> > //===
>> >
>> ----------------------------------------------------------------------===/
>> > /
>> >
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > -
>> > #include "string"
>> > #include "cstdlib"
>> > #include "cwchar"
>> >
>> > Modified: libcxx/trunk/src/valarray.cpp
>> > URL:
>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/valarray.cpp?rev
>> > =215740&r1=215739&r2=215740&view=diff
>> >
>> ==========================================================================
>> > ====
>> > --- libcxx/trunk/src/valarray.cpp (original)
>> > +++ libcxx/trunk/src/valarray.cpp Fri Aug 15 12:58:56 2014
>> > @@ -7,8 +7,6 @@
>> > //
>> > //===
>> >
>> ----------------------------------------------------------------------===/
>> > /
>> >
>> > -#define _LIBCPP_EXTERN_TEMPLATE(...) extern template __VA_ARGS__;
>> > -
>> > #include "valarray"
>> >
>> > _LIBCPP_BEGIN_NAMESPACE_STD
>> >
>> > _______________________________________________
>> > cfe-commits mailing list
>> > cfe-commits at cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140816/3c9355ca/attachment.html>
More information about the cfe-commits
mailing list