Hi,
When I compile the attached code, I find that one instantiation of
vector::_M_fill_insert is double the size of the other even though the
semantics should be the same:
$ clang++ -O3 -g -c insert.cpp
$ nm insert.o --size-sort -Ctd
0000000000000079 W std::vector<A, std::allocator<A> > f<A>()
0000000000000079 W std::vector<long, std::allocator<long> > f<long>()
0000000000001765 W std::vector<long, std::allocator<long>
>::_M_fill_insert(__gnu_cxx::__normal_iterator<long*, std::vector<long,
std::allocator<long> > >, unsigned long, long const&)
0000000000003638 W std::vector<A, std::allocator<A>
>::_M_fill_insert(__gnu_cxx::__normal_iterator<A*, std::vector<A,
std::allocator<A> > >, unsigned long, A const&)
What is the reason for this? I would expect that a class trivially
containing one member would be treated the same as just the member.
I'm using clang 10 on Ubuntu 20.04.
Best regards,
Marcel
#include <vector>
template<class T>
std::vector<T> f()
{
std::vector<T> a;
a.resize(10000, 1);
return a;
}
class A
{
public:
long a;
A(long a) : a(a) {}
};
template std::vector<long> f();
template std::vector<A> f();
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