Boost C++ Libraries: Ticket #11897: Compile failure in type_traits_detail::mp_valid_impl with CUDA 7.0

Fri, 08 Jan 2016 14:50:20 GMT

This bug was introduced in 1.60. 1.59 is working fine. As the following code shows, the problem is related to variadic templates:

#include <type_traits>
template<template<class...> class F, class... T>
struct mp_valid_impl
{
    template<template<class...> class G, class = G<T...>>
    static int check(int);
    template<template<class...> class>
    static bool check(...);
    using type = decltype(check<F>(0));
};
template<template<class...> class F, class T>
struct mp_valid_impl2
{
    template<template<class...> class G, class = G<T>>
    static int check(int);
    template<template<class...> class>
    static bool check(...);
    using type = decltype(check<F>(0));
};
template<template<class> class F, class T>
struct mp_valid_impl3
{
    template<template<class> class G, class = G<T>>
    static int check(int);
    template<template<class> class>
    static bool check(...);
    using type = decltype(check<F>(0));
};
template<typename T>
struct MetaFunc{};
int main(){
    typename mp_valid_impl<MetaFunc, int>::type i;
    typename mp_valid_impl2<MetaFunc, int>::type i2;
    typename mp_valid_impl3<MetaFunc, int>::type i3;
}

Output:

BoostMpValid.cu(12): error: no instance of overloaded function "mp_valid_impl<F, T...>::check [with F=MetaFunc, T=<int>]" matches the argument list
            argument types are: (int)
          detected during instantiation of class "mp_valid_impl<F, T...> [with F=MetaFunc, T=<int>]"
(44): here
BoostMpValid.cu(24): error: no instance of overloaded function "mp_valid_impl2<F, T>::check [with F=MetaFunc, T=int]" matches the argument list
            argument types are: (int)
          detected during instantiation of class "mp_valid_impl2<F, T> [with F=MetaFunc, T=int]"
(45): here
BoostMpValid.cu(46): warning: variable "i3" was declared but never referenced

So only the non-variadic version works. A simple workaround is probably to deactivate variadic templates by defining BOOST_NO_CXX11_VARIADIC_TEMPLATES for nvcc < 7.5. 7.5 is working so this can be used there.

Fri, 08 Jan 2016 15:05:34 GMT

Possible workaround: Add the following to the end of config/compiler/nvcc.hpp;

// A bug in version 7.0 of CUDA prevents use of variadic templates in some occasions
// https://svn.boost.org/trac/boost/ticket/11897
// This is fixed in 7.5. As the following version macro was introduced in 7.5 an existance
// check is enough to detect versions < 7.5
#ifndef __CUDACC_VER__
#   define BOOST_NO_CXX11_VARIADIC_TEMPLATES
#endif

John Maddock — Sun, 10 Jan 2016 12:14:50 GMT

Many thanks for investigating this so thoroughly. My only worry about setting BOOST_NO_CXX11_VARIADIC_TEMPLATES as a workaround, is that it may disable otherwise working code in other library interfaces. Does the patch below fix things?

index 5c4303b..4a26d92 100644
--- a/include/boost/type_traits/common_type.hpp
+++ b/include/boost/type_traits/common_type.hpp
@@ -12,12 +12,13 @@
 #include <boost/config.hpp>
 #include <boost/type_traits/decay.hpp>
 #include <boost/type_traits/declval.hpp>
+#include <boost/detail/workaround.hpp>
 #if defined(BOOST_NO_CXX11_DECLTYPE)
 #include <boost/type_traits/detail/common_type_impl.hpp>
 #endif
-#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !BOOST_WORKAROUND(__CUDACC_VER__,  < 70500)
 #include <boost/type_traits/detail/mp_defer.hpp>
 #endif
@@ -26,7 +27,7 @@ namespace boost
 // variadic common_type
-#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !BOOST_WORKAROUND(__CUDACC_VER__,  < 70500)
 template<class... T> struct common_type
 {

Mon, 11 Jan 2016 12:38:28 GMT

I was proposing to disable this as this is 1 case where variadic templates fail in NVCC 7.0 so I would not rely on its correctness and avoid it.

The proposed patch of yours does not work for 2 reasons: 1) You forgot one #if on line 89 2) The symbol is undefined in 7.0 and prior. Due to the check in BOOST_WORKAROUND for the existance and !=0 of the symbol it will always yield false. I don't see a good way to use that macro here. Using the plain defined(...) or ...>=70500 works.

Mon, 11 Jan 2016 12:39:49 GMT

Note that there is already a check in that form: #if !defined(BOOST_MSVC)

BOOST_MSVC > 1800

So using the >= would probably be ok

a.huebl@… — Mon, 11 Jan 2016 13:15:03 GMT

Careful with BOOST_WORKAROUND(__CUDACC_VER__, < 70500) please, __CUDACC_VER__ is first defined in CUDA 7.5 and will evaluate to undefined in previous versions. I guess BOOST_WORKAROUND will not evaluate to true in such a case.

anonymous — Mon, 11 Jan 2016 13:50:37 GMT

Careful with BOOST_WORKAROUND(CUDACC_VER, < 70500) please, CUDACC_VER is first defined in CUDA 7.5 and will evaluate to undefined in previous versions. I guess BOOST_WORKAROUND will not evaluate to true in such a case.

That's what we want - when CUDACC_VER is not defined it evaluates as 0 when used in a conditional (std mandated behaviour). So if CUDACC_VER is either undefined or less than the specified version then !BOOST_WORKAROUND(CUDACC_VER, < 70500) is false and the variadic template branch is not taken.

So 2 questions:

1) Is there any evidence that variadic template support is causing issues elsewhere in Boost?

2) If I update the patch as below, can someone please test it it?

index c887a89..2b85a39 100644
--- a/include/boost/type_traits/common_type.hpp
+++ b/include/boost/type_traits/common_type.hpp
@@ -18,7 +18,7 @@
 #include <boost/type_traits/detail/common_type_impl.hpp>
 #endif
-#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !BOOST_WORKAROUND(__CUDACC_VER__,  < 70500)
 #include <boost/type_traits/detail/mp_defer.hpp>
 #endif
@@ -27,7 +27,7 @@ namespace boost
 // variadic common_type
-#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !BOOST_WORKAROUND(__CUDACC_VER__,  < 70500)
 template<class... T> struct common_type
 {
@@ -86,7 +86,7 @@ namespace type_traits_detail
 #if !defined(BOOST_NO_CXX11_DECLTYPE)
-#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
+#if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES) && !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !BOOST_WORKAROUND(__CUDACC_VER__,  < 70500)
 #if !defined(BOOST_MSVC) || BOOST_MSVC > 1800

Mon, 11 Jan 2016 14:57:23 GMT

Yes, but the implementation of BOOST_WORKAROUND is:

#  define BOOST_WORKAROUND(symbol, test)                \
         ((symbol ## _WORKAROUND_GUARD + 0 == 0) &&     \
         (symbol != 0) && (1 % (( (symbol test) ) + 1)))

There is a check if that symbol evaluates to 0 causing the failure I described above. This is why BOOST_WORKAROUND cannot be used for this!

So:
1) Currently not. But similar uses of variadic templates will probably fail. Currently nothing else uses mp_defer (1.60) but other code in future versions may use that as well and run into the same bug.
2) No because BOOST_WORKAROUND always evaluates to false for this. Prior to 7.5 the symbol is undefined causing the (symbol != 0) check to fail, and in >=7.5 the 2nd part of the check will fail.

status changed; resolution set

John Maddock — Tue, 12 Jan 2016 16:43:40 GMT

status new → closed
resolution → fixed

OK, I've changed Boost.Config.

Please see https://github.com/boostorg/config/commit/2090da494ebe0bd79997234a9733191eac425564 and verify that this works for you.

Wed, 13 Jan 2016 08:25:28 GMT

Tested with CUDA 7.0 and 7.5 and verified that this works

Thanks for including the fix

sharvil — Tue, 19 Jan 2016 09:57:48 GMT

Apple LLVM version 7.0.2 (clang-700.1.81) is also affected by this.

John Maddock — Tue, 19 Jan 2016 10:06:28 GMT

Apple LLVM version 7.0.2 (clang-700.1.81) is also affected by this.

Can you be more specific? Do you mean nvcc on top of clang or just regular clang as shipped by Apple?

sharvil — Tue, 19 Jan 2016 19:05:08 GMT

Replying to johnmaddock:

Apple LLVM version 7.0.2 (clang-700.1.81) is also affected by this.

Can you be more specific? Do you mean nvcc on top of clang or just regular clang as shipped by Apple?

Just regular clang as shipped by Apple.

Michel Morin — Wed, 20 Jan 2016 10:28:14 GMT

Just regular clang as shipped by Apple.

With OP's test case, I was not able to reproduce the error on Apple Clang. Do you have a test case?

Thanks.

$ clang++ --version
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.2.0
Thread model: posix
$ clang++ -std=c++11 -I boost_1_60_0/ -xc++ -
#include <boost/type_traits/common_type.hpp>
#include <cstdint>
int main(){
    boost::common_type<int_least64_t, int_least64_t, intmax_t>::type i;
}
$ echo $?
0

anonymous — Wed, 20 Jan 2016 10:35:08 GMT

Regression tests for Clang version 7.0.2 (clang-700.1.81) all seem to be passing as well...

sharvil — Fri, 22 Jan 2016 02:44:13 GMT

Yeah, that test case does work. I'll try to extract the minimum piece of code that triggers this from our project over the weekend. But, we did manage to unblock our builds by disabling variadic templates.

antar1nd — Mon, 01 Feb 2016 09:11:59 GMT

On OSX, it can be reproduced if you compile it for objective-c++ .

#import <Foundation/Foundation.h>
#include <boost/type_traits/common_type.hpp>
int main(int argc, const char * argv[]) {
    boost::common_type<int_least64_t, int_least64_t, intmax_t>::type i;
    return 0;
}

Compiling the above results in :

$ clang++ -std=c++11 -I boost_1_60_0/ -ObjC++ test.mm
In file included from test.mm:2:
In file included from boost_1_60_0/boost/type_traits/common_type.hpp:21:
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:28:5: warning: declaration does not declare anything [-Wmissing-declarations]
    static boost::true_type check(int);
    ^~~~~~~~~~~~~~~~~~~~~~~
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:31:5: warning: declaration does not declare anything [-Wmissing-declarations]
    static boost::false_type check(...);
    ^~~~~~~~~~~~~~~~~~~~~~~~
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:33:27: error: use of undeclared identifier 'check'
    using type = decltype(check<F>(0));
                          ^
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:33:33: error: cannot refer to class template 'F' without a template argument list
    using type = decltype(check<F>(0));
                                ^
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:24:35: note: template is declared here
template<template<class...> class F, class... T>
                                  ^
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:37:1: error: no type named 'type' in 'boost::type_traits_detail::mp_valid_impl<common_type_fold, long long, long long, long>'
using mp_valid = typename mp_valid_impl<F, T...>::type;
^~~~~
boost_1_60_0/boost/type_traits/detail/mp_defer.hpp:50:95: note: in instantiation of template type alias 'mp_valid' requested here
template<template<class...> class F, class... T> using mp_defer = typename boost::conditional<mp_valid<F, T...>::value, mp_defer_impl<F, T...>, mp_empty>::type;
                                                                                              ^
boost_1_60_0/boost/type_traits/common_type.hpp:47:55: note: in instantiation of template type alias 'mp_defer' requested here
struct common_type<T1, T2, T...>: type_traits_detail::mp_defer<type_traits_detail::common_type_fold, T1, T2, T...>
                                                      ^
test.mm:5:9: note: in instantiation of template class 'boost::common_type<long long, long long, long>' requested here
        boost::common_type<int_least64_t, int_least64_t, intmax_t>::type i;
               ^
2 warnings and 3 errors generated.

The root cause is the expansion of a macro "check" defined in the OSX_SDK_10.11's AssertMacros.h . Defining either BOOST_NO_CXX11_TEMPLATE_ALIASES or BOOST_NO_CXX11_VARIADIC_TEMPLATES excludes mp_defer.hpp therefore that works as a workaround. What also works is #undef check before this inclusion.

antar1nd — Mon, 01 Feb 2016 09:28:33 GMT

Seems to be fixed in develop : https://github.com/boostorg/type_traits/commit/f80cbb0dad16f974815a4ad8208f056ec58c9efc

John Maddock — Mon, 01 Feb 2016 18:29:37 GMT

The check macro issue is presumably a whole different issue, but if not then yes, this should be fixed in the next release.

bchretien — Wed, 05 Oct 2016 15:49:12 GMT

Apparently the bug is back with CUDA 8.0 (tested with Boost 1.61.0). With the original repro code:

$ /usr/local/cuda-7.5/bin/nvcc bug.cu -std=c++11
// No issue
$ /usr/local/cuda-8.0/bin/nvcc bug.cu -std=c++11
error: class "boost::common_type<int_least64_t, int_least64_t, intmax_t>" has no member "type"

milestone changed

John Maddock — Sat, 29 Oct 2016 08:45:34 GMT

milestone To Be Determined → Boost 1.63.0

You're right - CUDA 8 has the same issue! I've just pushed some changes to Boost.Config develop to fix this.

bchretien — Tue, 29 Nov 2016 07:44:41 GMT

I forwarded the issue to the NVIDIA developers, they fixed the problem for the next CUDA release.