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Merge pull request #119 from cmazakas/laundry

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Fix `-Wmaybe-unitialized` warning in gcc-12
This commit is contained in:
Peter Dimov
2022-06-07 20:55:32 +03:00
committed by GitHub
parent e690e8910c 613a997694
commit 4b56bfac05
1 changed files with 21 additions and 4 deletions
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25
include/boost/unordered/detail/implementation.hpp
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@ -1548,6 +1548,21 @@ namespace boost {
// If an exception is thrown between these two calls, use
// 'cleanup_spare_functions' to destroy the unused constructed functions.
#if defined(_GLIBCXX_HAVE_BUILTIN_LAUNDER)
// gcc-12 warns when accessing the `current_functions` of our `functions`
// class below with `-Wmaybe-unitialized`. By laundering the pointer, we
// silence the warning and assure the compiler that a valid object exists
// in that region of storage. This warning is also generated in C++03
// which does not have `std::launder`. The compiler builtin is always
// available, regardless of the C++ standard used when compiling.
template <class T> T* launder(T* p) BOOST_NOEXCEPT
{
return __builtin_launder(p);
}
#else
template <class T> T* launder(T* p) BOOST_NOEXCEPT { return p; }
#endif
template <class H, class P> class functions
{
public:
@ -1604,14 +1619,16 @@ namespace boost {
function_pair const& current_functions() const
{
return *static_cast<function_pair const*>(
static_cast<void const*>(funcs_[current_ & 1].address()));
return *::boost::unordered::detail::launder(
static_cast<function_pair const*>(
static_cast<void const*>(funcs_[current_ & 1].address())));
}
function_pair& current_functions()
{
return *static_cast<function_pair*>(
static_cast<void*>(funcs_[current_ & 1].address()));
return *::boost::unordered::detail::launder(
static_cast<function_pair*>(
static_cast<void*>(funcs_[current_ & 1].address())));
}
void construct_spare_functions(function_pair const& f)