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libstdc++: Use RAII in _Hashtable

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Use scoped guard types to clean up if an exception is thrown. This
allows some try-catch blocks to be removed.

libstdc++-v3/ChangeLog:

	* include/bits/hashtable.h (operator=(const _Hashtable&)): Use
	RAII instead of try-catch.
	(_M_assign(_Ht&&, _NodeGenerator&)): Likewise.

Reviewed-by: François Dumont <fdumont@gcc.gnu.org>
This commit is contained in:
Jonathan Wakely 2024-11-01 22:20:22 +00:00 committed by Jonathan Wakely
parent e717c322c6
commit d2970e86c4
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1 changed files with 56 additions and 45 deletions
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101
libstdc++-v3/include/bits/hashtable.h
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@ -1307,17 +1307,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_bucket_count = __ht._M_bucket_count;
_M_element_count = __ht._M_element_count;
_M_rehash_policy = __ht._M_rehash_policy;
__try
{
_M_assign(__ht);
}
__catch(...)
{
// _M_assign took care of deallocating all memory. Now we
// must make sure this instance remains in a usable state.
_M_reset();
__throw_exception_again;
}
struct _Guard
{
~_Guard() { if (_M_ht) _M_ht->_M_reset(); }
_Hashtable* _M_ht;
};
// If _M_assign exits via an exception it will have deallocated
// all memory. This guard will ensure *this is in a usable state.
_Guard __guard{this};
_M_assign(__ht);
__guard._M_ht = nullptr;
return *this;
}
std::__alloc_on_copy(__this_alloc, __that_alloc);
@ -1390,46 +1390,57 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::
_M_assign(_Ht&& __ht, _NodeGenerator& __node_gen)
{
__buckets_ptr __buckets = nullptr;
if (!_M_buckets)
_M_buckets = __buckets = _M_allocate_buckets(_M_bucket_count);
__try
struct _Guard
{
~_Guard()
{
if (!__ht._M_before_begin._M_nxt)
return;
using _FromVal = __conditional_t<is_lvalue_reference<_Ht>::value,
const value_type&, value_type&&>;
// First deal with the special first node pointed to by
// _M_before_begin.
__node_ptr __ht_n = __ht._M_begin();
__node_ptr __this_n
= __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));
this->_M_copy_code(*__this_n, *__ht_n);
_M_update_bbegin(__this_n);
// Then deal with other nodes.
__node_ptr __prev_n = __this_n;
for (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())
if (_M_ht)
{
__this_n = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));
__prev_n->_M_nxt = __this_n;
this->_M_copy_code(*__this_n, *__ht_n);
size_type __bkt = _M_bucket_index(*__this_n);
if (!_M_buckets[__bkt])
_M_buckets[__bkt] = __prev_n;
__prev_n = __this_n;
_M_ht->clear();
if (_M_dealloc_buckets)
_M_ht->_M_deallocate_buckets();
}
}
__catch(...)
_Hashtable* _M_ht = nullptr;
bool _M_dealloc_buckets = false;
};
_Guard __guard;
if (!_M_buckets)
{
clear();
if (__buckets)
_M_deallocate_buckets();
__throw_exception_again;
_M_buckets = _M_allocate_buckets(_M_bucket_count);
__guard._M_dealloc_buckets = true;
}
if (!__ht._M_before_begin._M_nxt)
return;
__guard._M_ht = this;
using _FromVal = __conditional_t<is_lvalue_reference<_Ht>::value,
const value_type&, value_type&&>;
// First deal with the special first node pointed to by
// _M_before_begin.
__node_ptr __ht_n = __ht._M_begin();
__node_ptr __this_n
= __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));
this->_M_copy_code(*__this_n, *__ht_n);
_M_update_bbegin(__this_n);
// Then deal with other nodes.
__node_ptr __prev_n = __this_n;
for (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())
{
__this_n = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));
__prev_n->_M_nxt = __this_n;
this->_M_copy_code(*__this_n, *__ht_n);
size_type __bkt = _M_bucket_index(*__this_n);
if (!_M_buckets[__bkt])
_M_buckets[__bkt] = __prev_n;
__prev_n = __this_n;
}
__guard._M_ht = nullptr;
}
template<typename _Key, typename _Value, typename _Alloc,