> > diff --git a/libstdc++-v3/include/bits/deque.tcc
> > b/libstdc++-v3/include/bits/deque.tcc
> > index deb010a0ebb..e56cd0b9319 100644
> > --- a/libstdc++-v3/include/bits/deque.tcc
> > +++ b/libstdc++-v3/include/bits/deque.tcc
> > @@ -955,6 +955,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
> > size_type __new_map_size = this->_M_impl._M_map_size
> > + std::max(this->_M_impl._M_map_size,
> > __nodes_to_add) + 2;
> > + if (__new_map_size > ((max_size() + __deque_buf_size(sizeof(_Tp)) - 1)
> > + / __deque_buf_size(sizeof(_Tp))) * 2)
> > + __builtin_unreachable ();
>
> I think it's worth avoiding the duplicate call, for -O0 -std=c++98.
> It makes the line shorter too:
>
> const size_t __bufsz = __deque_buf_size(sizeof(_Tp));
> if (__new_map_size > ((max_size() + __bufsz - 1) / __bufsz) * 2)
> __builtin_unreachable();
This looks better, in fact that what I inteded with that forgotten
veriable. I think __deque_buf_size is a constexpr and gets replaced by
constant.
I wonder why "const" is useful here. Also I wonder if there is any
difference between size_type and size_t, or it can be used
interchangeably?
For -O0 we do keep the cmp instruction around, but "optimize away" the
conditonal jump to unreachable, which is bit odd. An option would be to
add ifdef __OPTIMIZE__ guards.
This is updated patch I am testing
diff --git a/libstdc++-v3/include/bits/deque.tcc
b/libstdc++-v3/include/bits/deque.tcc
index deb010a0ebb..ee03c917a29 100644
--- a/libstdc++-v3/include/bits/deque.tcc
+++ b/libstdc++-v3/include/bits/deque.tcc
@@ -956,6 +956,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
+ std::max(this->_M_impl._M_map_size,
__nodes_to_add) + 2;
+ const size_t __bufsz = __deque_buf_size(sizeof(_Tp));
+ if (__new_map_size > ((max_size() + __bufsz - 1) / __bufsz) * 2)
+ __builtin_unreachable();
+
_Map_pointer __new_map = this->_M_allocate_map(__new_map_size);
__new_nstart = __new_map + (__new_map_size - __new_num_nodes) / 2
+ (__add_at_front ? __nodes_to_add : 0);
diff --git a/libstdc++-v3/include/bits/stl_deque.h
b/libstdc++-v3/include/bits/stl_deque.h
index c617933bd81..dd1212793de 100644
--- a/libstdc++-v3/include/bits/stl_deque.h
+++ b/libstdc++-v3/include/bits/stl_deque.h
@@ -1266,7 +1266,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_GLIBCXX_NODISCARD
size_type
size() const _GLIBCXX_NOEXCEPT
- { return this->_M_impl._M_finish - this->_M_impl._M_start; }
+ {
+ size_type __sz = this->_M_impl._M_finish - this->_M_impl._M_start;
+ if (__sz > max_size ())
+ __builtin_unreachable ();
+ return __sz;
+ }
/** Returns the size() of the largest possible %deque. */
_GLIBCXX_NODISCARD
