The following program:

------
#include <functional>

struct Foo {
    std::function <void(double &)> f;
    Foo (
        std::function <void(double &)> const & f_ 
    ) : f(f_) {}
};

struct Bar {
    Foo foo;
    Bar() :
        foo([](auto & num) {})
    {}
};

int main() {
    Bar bar;
}
------

segfaults gdb on startup:

$ gdb test19
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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Reading symbols from test19...Segmentation fault

However, when changing the line

        foo([](auto & num) {})

to

        foo([](double & num) {})

gdb works as normal.  In case it helps:

GNU gdb (Gentoo 7.7.1 p1) 7.7.1
gcc version 4.9.2 (Gentoo 4.9.2 p1.0, pie-0.6.1)