https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393
Bug ID: 65393
Summary: std::thread shared_ptr inefficiency
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: klemensbaum at gmail dot com
The std::thread implementation passes around shared_ptr instances by value in
multiple places where they could be moved:
1)
in the function
void
thread::_M_start_thread(__shared_base_type __b)
the line
_M_start_thread(__b, nullptr);
could be changed to
_M_start_thread(std::move(__b), nullptr);
or alternatively take __shared_base_type by "universal reference" and forward
it into the other _M_start_thread overload.
2)
in the function
void
thread::_M_start_thread(__shared_base_type __b, void (*)())
the lines
__b->_M_this_ptr = __b;
int __e = __gthread_create(&_M_id._M_thread,
&execute_native_thread_routine, __b.get());
could be changed to
auto __p = __b.get();
__b->_M_this_ptr = std::move(__b);
int __e = __gthread_create(&_M_id._M_thread,
&execute_native_thread_routine, __p);
3) Finally, the use of shared_ptr seems wholly unnecessarily. This can likely
be implemented more cleanly with unique_ptr, and more efficiently, since it
avoids the extra heap space for the reference count and all of the atomic ops.
