https://gcc.gnu.org/g:bfe05fbb30594b9f1fdfba32f3fc7b317e5158e0
commit r12-10231-gbfe05fbb30594b9f1fdfba32f3fc7b317e5158e0
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date: Fri Sep 29 10:30:41 2023 +0100
libstdc++: Ensure active union member is correctly set
This patch ensures that the union members for std::string and
std::variant are always properly set when a change occurs.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h: (basic_string(basic_string&&)):
Activate _M_local_buf when needed.
(basic_string(basic_string&&, const _Alloc&)): Likewise.
* include/bits/basic_string.tcc: (basic_string::swap): Likewise.
* include/std/variant: (__detail::__variant::__construct_n): New.
(__detail::__variant::__emplace): Use __construct_n.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
(cherry picked from commit 28adad7a32ed92a3c0906b38411c4ed686bbacc5)
Diff:
---
libstdc++-v3/include/bits/basic_string.h | 6 ++++--
libstdc++-v3/include/bits/basic_string.tcc | 4 ++++
libstdc++-v3/include/std/variant | 32 ++++++++++++++++++++++++++++--
3 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/bits/basic_string.h
b/libstdc++-v3/include/bits/basic_string.h
index 9a6fe883b6c..3f38f20dd18 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -680,6 +680,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{
if (__str._M_is_local())
{
+ (void)_M_use_local_data();
traits_type::copy(_M_local_buf, __str._M_local_buf,
__str.length() + 1);
}
@@ -693,7 +694,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
// basic_stringbuf relies on writing into unallocated capacity so
// we mess up the contents if we put a '\0' in the string.
_M_length(__str.length());
- __str._M_data(__str._M_local_data());
+ __str._M_data(__str._M_use_local_data());
__str._M_set_length(0);
}
@@ -719,6 +720,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{
if (__str._M_is_local())
{
+ (void)_M_use_local_data();
traits_type::copy(_M_local_buf, __str._M_local_buf,
__str.length() + 1);
_M_length(__str.length());
@@ -730,7 +732,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_M_data(__str._M_data());
_M_length(__str.length());
_M_capacity(__str._M_allocated_capacity);
- __str._M_data(__str._M_local_buf);
+ __str._M_data(__str._M_use_local_data());
__str._M_set_length(0);
}
else
diff --git a/libstdc++-v3/include/bits/basic_string.tcc
b/libstdc++-v3/include/bits/basic_string.tcc
index 48fa28e6466..24465dab102 100644
--- a/libstdc++-v3/include/bits/basic_string.tcc
+++ b/libstdc++-v3/include/bits/basic_string.tcc
@@ -79,6 +79,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
else if (__s.length())
{
+ (void)_M_use_local_data();
traits_type::copy(_M_local_buf, __s._M_local_buf,
__s.length() + 1);
_M_length(__s.length());
@@ -87,6 +88,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
else if (length())
{
+ (void)__s._M_use_local_data();
traits_type::copy(__s._M_local_buf, _M_local_buf,
length() + 1);
__s._M_length(length());
@@ -97,6 +99,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
else
{
const size_type __tmp_capacity = __s._M_allocated_capacity;
+ (void)__s._M_use_local_data();
traits_type::copy(__s._M_local_buf, _M_local_buf,
length() + 1);
_M_data(__s._M_data());
@@ -108,6 +111,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
const size_type __tmp_capacity = _M_allocated_capacity;
if (__s._M_is_local())
{
+ (void)_M_use_local_data();
traits_type::copy(_M_local_buf, __s._M_local_buf,
__s.length() + 1);
__s._M_data(_M_data());
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 2e784c744d3..64145da12bb 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -321,6 +321,33 @@ namespace __variant
__get(_Variant&& __v) noexcept
{ return __variant::__get_n<_Np>(std::forward<_Variant>(__v)._M_u); }
+ // Gets the _Uninitialized to construct into for __u.
+ template<size_t _Np, typename _Union>
+ constexpr decltype(auto)
+ __construct_n(_Union& __u) noexcept
+ {
+ if constexpr (_Np == 0)
+ return &__u._M_first;
+ else if constexpr (_Np == 1)
+ {
+ std::_Construct(&__u._M_rest);
+ return &__u._M_rest._M_first;
+ }
+ else if constexpr (_Np == 2)
+ {
+ std::_Construct(&__u._M_rest);
+ std::_Construct(&__u._M_rest._M_rest);
+ return &__u._M_rest._M_rest._M_first;
+ }
+ else
+ {
+ std::_Construct(&__u._M_rest);
+ std::_Construct(&__u._M_rest._M_rest);
+ std::_Construct(&__u._M_rest._M_rest._M_rest);
+ return __variant::__construct_n<_Np - 3>(__u._M_rest._M_rest._M_rest);
+ }
+ }
+
template<typename... _Types>
struct _Traits
{
@@ -537,8 +564,9 @@ namespace __variant
__emplace(_Variant_storage<_Triv, _Types...>& __v, _Args&&... __args)
{
__v._M_reset();
- auto* __addr = std::__addressof(__variant::__get_n<_Np>(__v._M_u));
- std::_Construct(__addr, std::forward<_Args>(__args)...);
+ auto* __addr = __variant::__construct_n<_Np>(__v._M_u);
+ std::_Construct(__addr, in_place_index<0>,
+ std::forward<_Args>(__args)...);
// Construction didn't throw, so can set the new index now:
__v._M_index = _Np;
}
