boostorg/container
1
0
Fork 1
mirror of https://github.com/boostorg/container.git synced 2025-08-01 13:34:30 +02:00
Code Issues Packages Projects Releases Wiki Activity

Improve short/long representation to avoid aliasing problems and disable "-Wmaybe-uninitialized" for compilers that have false positives.

Browse Source
This commit is contained in:
Ion Gaztañaga
2018-09-15 01:10:50 +02:00
parent f28fe5d33e
commit cce2ef763a
1 changed files with 105 additions and 69 deletions
Download Patch File Download Diff File Expand all files Collapse all files

174
include/boost/container/string.hpp
View File

@@ -98,27 +98,25 @@ class basic_string_base
basic_string_base()
: members_()
{ init(); }
{}
explicit basic_string_base(const allocator_type& a)
: members_(a)
{ init(); }
{}
explicit basic_string_base(BOOST_RV_REF(allocator_type) a)
: members_(boost::move(a))
{ this->init(); }
{}
basic_string_base(const allocator_type& a, size_type n)
: members_(a)
{
this->init();
this->allocate_initial_block(n);
}
explicit basic_string_base(size_type n)
: members_()
{
this->init();
this->allocate_initial_block(n);
}
@@ -140,6 +138,11 @@ class basic_string_base
pointer start;
long_t()
: is_short(0)
{}
long_t(size_type len, size_type stor, pointer ptr)
: is_short(0), length(len), storage(stor), start(ptr)
{}
long_t(const long_t &other)
@@ -190,35 +193,49 @@ class basic_string_base
value_type data[UnalignedFinalInternalBufferChars];
};
union repr_t
union repr_t_size_t
{
long_raw_t r;
short_t s;
};
const short_t &short_repr() const
{ return s; }
const long_t &long_repr() const
{ return *static_cast<const long_t*>(static_cast<const void*>(r.data)); }
short_t &short_repr()
{ return s; }
long_t &long_repr()
{ return *static_cast<long_t*>(static_cast<void*>(&r)); }
union repr_t
{
long_raw_t r_aligner;
short_t s_aligner;
unsigned char data[sizeof(repr_t_size_t)];
};
struct members_holder
: public Allocator
{
void init()
{
short_t &s = *::new(this->m_repr.data) short_t;
s.h.is_short = 1;
s.h.length = 0;
}
members_holder()
: Allocator()
{}
{ this->init(); }
template<class AllocatorConvertible>
explicit members_holder(BOOST_FWD_REF(AllocatorConvertible) a)
: Allocator(boost::forward<AllocatorConvertible>(a))
{}
{ this->init(); }
const short_t *pshort_repr() const
{ return reinterpret_cast<const short_t*>(m_repr.data); }
const long_t *plong_repr() const
{ return reinterpret_cast<const long_t*>(m_repr.data); }
short_t *pshort_repr()
{ return reinterpret_cast<short_t*>(m_repr.data); }
long_t *plong_repr()
{ return reinterpret_cast<long_t*>(m_repr.data); }
repr_t m_repr;
} members_;
@@ -246,32 +263,43 @@ class basic_string_base
return hdr.is_short != 0;
}
void is_short(bool yes)
short_t *make_short()
{
const bool was_short = this->is_short();
if(yes && !was_short){
allocator_traits_type::destroy
( this->alloc()
, static_cast<long_t*>(static_cast<void*>(&this->members_.m_repr.r))
);
this->members_.m_repr.s.h.is_short = true;
}
else if(!yes && was_short){
allocator_traits_type::construct
( this->alloc()
, static_cast<long_t*>(static_cast<void*>(&this->members_.m_repr.r))
);
this->members_.m_repr.s.h.is_short = false;
}
BOOST_ASSERT(!this->is_short());
allocator_traits_type::destroy
( this->alloc()
, reinterpret_cast<long_t*>(this->members_.m_repr.data)
);
short_t *ps = ::new(this->members_.m_repr.data) short_t;
ps->h.is_short = 1;
return ps;
}
private:
void init()
long_t *make_long()
{
this->members_.m_repr.s.h.is_short = 1;
this->members_.m_repr.s.h.length = 0;
BOOST_ASSERT(this->is_short());
long_t *pl = reinterpret_cast<long_t*>(this->members_.m_repr.data);
allocator_traits_type::construct(this->alloc(), pl);
//is_short flag is written in the constructor
return pl;
}
long_t *make_long_if_needed()
{
if (this->is_short()){
this->members_.pshort_repr()->~short_t();
}
return this->make_long();
}
short_t *make_short_if_needed()
{
if (!this->is_short()){
this->members_.plong_repr()->~long_t();
}
return this->make_short();
}
protected:
typedef dtl::integral_constant<unsigned,
@@ -334,7 +362,7 @@ class basic_string_base
size_type new_cap = this->next_capacity(n);
pointer reuse = 0;
pointer p = this->allocation_command(allocate_new, n, new_cap, reuse);
this->is_short(false);
this->make_long();
this->priv_long_addr(p);
this->priv_long_size(0);
this->priv_storage(new_cap);
@@ -356,10 +384,16 @@ class basic_string_base
{ return this->priv_storage() - 1; }
pointer priv_short_addr() const
{ return pointer_traits::pointer_to(const_cast<value_type&>(this->members_.m_repr.short_repr().data[0])); }
{ return pointer_traits::pointer_to(const_cast<value_type&>(this->members_.pshort_repr()->data[0])); }
//GCC seems a bit confused about uninitialized accesses
#if defined(BOOST_GCC) && (BOOST_GCC >= 40700)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
pointer priv_long_addr() const
{ return this->members_.m_repr.long_repr().start; }
{ return this->members_.plong_repr()->start; }
pointer priv_addr() const
{
@@ -378,7 +412,7 @@ class basic_string_base
}
void priv_long_addr(pointer addr)
{ this->members_.m_repr.long_repr().start = addr; }
{ this->members_.plong_repr()->start = addr; }
size_type priv_storage() const
{ return this->is_short() ? priv_short_storage() : priv_long_storage(); }
@@ -387,7 +421,7 @@ class basic_string_base
{ return InternalBufferChars; }
size_type priv_long_storage() const
{ return this->members_.m_repr.long_repr().storage; }
{ return this->members_.plong_repr()->storage; }
void priv_storage(size_type storage)
{
@@ -397,17 +431,17 @@ class basic_string_base
void priv_long_storage(size_type storage)
{
this->members_.m_repr.long_repr().storage = storage;
this->members_.plong_repr()->storage = storage;
}
size_type priv_size() const
{ return this->is_short() ? this->priv_short_size() : this->priv_long_size(); }
size_type priv_short_size() const
{ return this->members_.m_repr.short_repr().h.length; }
{ return this->members_.pshort_repr()->h.length; }
size_type priv_long_size() const
{ return this->members_.m_repr.long_repr().length; }
{ return this->members_.plong_repr()->length; }
void priv_size(size_type sz)
{
@@ -418,14 +452,14 @@ class basic_string_base
}
void priv_short_size(size_type sz)
{
this->members_.m_repr.s.h.length = (unsigned char)sz;
}
{ this->members_.pshort_repr()->h.length = (unsigned char)sz; }
void priv_long_size(size_type sz)
{
this->members_.m_repr.long_repr().length = sz;
}
{ this->members_.plong_repr()->length = sz; }
#if defined(BOOST_GCC) && (BOOST_GCC >= 40700)
#pragma GCC diagnostic pop
#endif
void swap_data(basic_string_base& other)
{
@@ -436,23 +470,23 @@ class basic_string_base
other.members_.m_repr = tmp;
}
else{
short_t short_backup(this->members_.m_repr.short_repr());
this->members_.m_repr.short_repr().~short_t();
::new(&this->members_.m_repr.long_repr()) long_t(other.members_.m_repr.long_repr());
other.members_.m_repr.long_repr().~long_t();
::new(&other.members_.m_repr.short_repr()) short_t(short_backup);
short_t short_backup(*this->members_.pshort_repr());
this->members_.pshort_repr()->~short_t();
::new(this->members_.plong_repr()) long_t(*other.members_.plong_repr());
other.members_.plong_repr()->~long_t();
::new(other.members_.pshort_repr()) short_t(short_backup);
}
}
else{
if(other.is_short()){
short_t short_backup(other.members_.m_repr.short_repr());
other.members_.m_repr.short_repr().~short_t();
::new(&other.members_.m_repr.long_repr()) long_t(this->members_.m_repr.long_repr());
this->members_.m_repr.long_repr().~long_t();
::new(&this->members_.m_repr.short_repr()) short_t(short_backup);
short_t short_backup(*other.members_.pshort_repr());
other.members_.pshort_repr()->~short_t();
::new(other.members_.plong_repr()) long_t(*this->members_.plong_repr());
this->members_.plong_repr()->~long_t();
::new(this->members_.pshort_repr()) short_t(short_backup);
}
else{
boost::adl_move_swap(this->members_.m_repr.long_repr(), other.members_.m_repr.long_repr());
boost::adl_move_swap(*this->members_.plong_repr(), *other.members_.plong_repr());
}
}
}
@@ -830,7 +864,7 @@ class basic_string
if(flag && this_alloc != x_alloc){
if(!this->is_short()){
this->deallocate_block();
this->is_short(true);
this->make_short();
Traits::assign(*this->priv_addr(), CharT(0));
this->priv_short_size(0);
}
@@ -1159,7 +1193,7 @@ class basic_string
Traits::copy( boost::movelib::to_raw_pointer(this->priv_short_addr())
, boost::movelib::to_raw_pointer(long_addr)
, long_size+1);
this->is_short(true);
this->make_short();
this->alloc().deallocate(long_addr, long_storage);
}
else{
@@ -1763,7 +1797,7 @@ class basic_string
this->priv_construct_null(new_start + new_length);
this->deallocate_block();
this->is_short(false);
this->make_long_if_needed();
this->priv_long_addr(new_start);
this->priv_long_size(new_length);
this->priv_long_storage(new_cap);
@@ -1782,7 +1816,9 @@ class basic_string
//Now initialize the new data
priv_uninitialized_copy(first, last, new_start + before);
this->priv_construct_null(new_start + (old_size + n));
this->is_short(false);
if(this->is_short())
this->members_.pshort_repr()->~short_t();
this->make_long_if_needed();
this->priv_long_addr(new_start);
this->priv_long_size(old_size + n);
this->priv_long_storage(new_cap);
@@ -2790,7 +2826,7 @@ class basic_string
this->priv_construct_null(new_start + new_length);
}
this->deallocate_block();
this->is_short(false);
this->make_long_if_needed();
this->priv_long_addr(new_start);
this->priv_long_size(new_length);
this->priv_storage(new_cap);