[Bug c++/53954] New: [C++11] Undefined reference to non-odr-used static const member variable of variadic class template in DSO with -flto and -Wl,--export-dynamic
ai.azuma at gmail dot com
gcc-bugzilla@gcc.gnu.org
Fri Jul 13 14:20:00 GMT 2012
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53954
Bug #: 53954
Summary: [C++11] Undefined reference to non-odr-used static
const member variable of variadic class template in
DSO with -flto and -Wl,--export-dynamic
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: ai.azuma@gmail.com
Created attachment 27785
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27785
Command-line log
The following code shows the problem with GCC 4.7.2 20120707 on
x86_64-unknown-linux-gnu.
//////////////////////////////////
// foo.cpp
template<typename...>
struct S
{
static const bool value = false;
};
void f() {
typedef decltype(S<>::value) B;
}
//////////////////////////////////
Obviously, `S<>::value' is not odr-used. Therefore, the program should not
require its definition. However, when a DSO is created from the above code with
GCC 4.7.2 20120707, `-flto' and `-Wl,--export-dynamic' options, it requires the
definition of `S<>::value'.
For example, the following command lines result in a link error.
$ g++ -std=c++11 -fPIC -flto -Wl,--export-dynamic -o libfoo.so -shared foo.cpp
$ g++ -std=c++11 -fPIC main.cpp -L. -lfoo
./libfoo.so: undefined reference to `S<>::value'
./libfoo.so: undefined reference to `S<>::value'
collect2: error: ld returned 1 exit status
where main.cpp is a trivial C++ source file like "int main(){}".
Note that neither GCC 4.6.4 20120706 nor 4.8.0 20120708 reproduces the problem.
Note also that the above reproducer originally comes from a likely C++ code
using `std::vector' and `-std=c++11' option, like the following;
/////////////////////
#include <vector>
void f()
{
std::vector<int> v;
v.push_back(0);
}
/////////////////////
When a DSO is created from this code with `-std=c++11', `-lfto' and
`-Wl,--export-dynamic' options, it requires the definition of
`std::allocator_traits<std::allocator<int> >::__construct_helper<int,
int>::value'.
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