The recent libsigc++-2.5.1 refuses to compile without -std=c++11 and it affects inkscape too:
shlomif@telaviv1:~$ g++ `pkg-config --cflags sigc++-2.0` sigcpp_test.cpp
In file included from /usr/include/sigc++-2.0/sigc++/adaptors/adaptor_trait.h:7:0,
from /usr/include/sigc++-2.0/sigc++/functors/slot.h:7,
from /usr/include/sigc++-2.0/sigc++/signal_base.h:27,
from /usr/include/sigc++-2.0/sigc++/signal.h:8,
from sigcpp_test.cpp:14:
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:91:36: error: ‘decltype’ has not been declared
static int check(X_functor* obj, decltype(&X_functor::operator()) p = nullptr
^
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:91:46: error: expected ‘)’
static int check(X_functor* obj, decltype(&X_functor::operator()) p = nullptr
^
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:91:46: error: expected ‘)’
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:91:46: error: expected initializer
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:96:44: error: ‘nullptr’ was not declared in this scope
= sizeof(check(static_cast<T_functor*>(nullptr))) == sizeof(int)
^
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:134:64: error: ‘&’ cannot appear in a constant-expression
typedef typename functor_trait<decltype(&T_functor::operator()), false, false
^
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:134:65: error: a function call cannot appear in a constant-expression
typedef typename functor_trait<decltype(&T_functor::operator()), false, false
^
/usr/include/sigc++-2.0/sigc++/functors/functor_trait.h:134:80: error: template argument 1 is invalid
ypename functor_trait<decltype(&T_functor::operator()), false, false>::result_t
^
shlomif@telaviv1:~$ g++ -std=c++11 `pkg-config --cflags sigc++-2.0` sigcpp_test.cpp
shlomif@telaviv1:~$ cat sigcpp_test.cpp
/*
* Building this using:
g++ `pkg-config --cflags sigc++-2.0` sigcpp_test.cpp
Results in an error.
* */
#include <stddef.h>
#include <string>
#if 0
#include <sigc++/sigc++.h>
#else
#include <sigc++/signal.h>
#endif
int main()
{
return 0;
}
=====================
The attached tentative patch fixes this problem.
Wow... this is actually a much bigger issue, because we deliberately haven't yet used any C++11 features directly in Inkscape.
We could, as you suggest, only enforce C++11 builds for people with new versions of libsigc++, but it makes me pretty nervous having to support two different C++ standards.
A proper fix would enforce C++11 builds for everyone, but this is problematic, because AFAIK older OS X releases don't provide compiler support for C++11.
I think this needs further discussion! :/