libstdc++: Avoid bogus warning in std::vector::insert [PR107852]

GCC assumes that any global variable might be modified by operator new,
and so in the testcase for this PR all data members get reloaded after
allocating new storage. By making local copies of the _M_start and
_M_finish members we avoid that, and then the compiler has enough info
to remove the dead branches that trigger bogus -Warray-bounds warnings.

libstdc++-v3/ChangeLog:

	PR libstdc++/107852
	PR libstdc++/106199
	PR libstdc++/100366
	* include/bits/vector.tcc (vector::_M_fill_insert): Copy
	_M_start and _M_finish members before allocating.
	(vector::_M_default_append): Likewise.
	(vector::_M_range_insert): Likewise.

(cherry picked from commit cca06f0d6d76b08ed4ddb7667eda93e2e9f2589e)

diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc
index 33faabf2eae572e8068838374ab8745b33a342ac..27ef1a4ee7fe59ce3a1f8d739f808ab807d4be72 100644 (file)
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -539,9 +539,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
              if (__elems_after > __n)
                {
                  _GLIBCXX_ASAN_ANNOTATE_GROW(__n);
-                 std::__uninitialized_move_a(this->_M_impl._M_finish - __n,
-                                             this->_M_impl._M_finish,
-                                             this->_M_impl._M_finish,
+                 std::__uninitialized_move_a(__old_finish - __n,
+                                             __old_finish,
+                                             __old_finish,
                                              _M_get_Tp_allocator());
                  this->_M_impl._M_finish += __n;
                  _GLIBCXX_ASAN_ANNOTATE_GREW(__n);
@@ -554,7 +554,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                {
                  _GLIBCXX_ASAN_ANNOTATE_GROW(__n);
                  this->_M_impl._M_finish =
-                   std::__uninitialized_fill_n_a(this->_M_impl._M_finish,
+                   std::__uninitialized_fill_n_a(__old_finish,
                                                  __n - __elems_after,
                                                  __x_copy,
                                                  _M_get_Tp_allocator());
@@ -569,9 +569,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
            }
          else
            {
+             // Make local copies of these members because the compiler thinks
+             // the allocator can alter them if 'this' is globally reachable.
+             pointer __old_start = this->_M_impl._M_start;
+             pointer __old_finish = this->_M_impl._M_finish;
+             const pointer __pos = __position.base();
+
              const size_type __len =
                _M_check_len(__n, "vector::_M_fill_insert");
-             const size_type __elems_before = __position - begin();
+             const size_type __elems_before = __pos - __old_start;
              pointer __new_start(this->_M_allocate(__len));
              pointer __new_finish(__new_start);
              __try
@@ -584,15 +590,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
                  __new_finish
                    = std::__uninitialized_move_if_noexcept_a
-                   (this->_M_impl._M_start, __position.base(),
-                    __new_start, _M_get_Tp_allocator());
+                   (__old_start, __pos, __new_start, _M_get_Tp_allocator());
 
                  __new_finish += __n;
 
                  __new_finish
                    = std::__uninitialized_move_if_noexcept_a
-                   (__position.base(), this->_M_impl._M_finish,
-                    __new_finish, _M_get_Tp_allocator());
+                   (__pos, __old_finish, __new_finish, _M_get_Tp_allocator());
                }
              __catch(...)
                {
@@ -606,12 +610,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                  _M_deallocate(__new_start, __len);
                  __throw_exception_again;
                }
-             std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
-                           _M_get_Tp_allocator());
+             std::_Destroy(__old_start, __old_finish, _M_get_Tp_allocator());
              _GLIBCXX_ASAN_ANNOTATE_REINIT;
-             _M_deallocate(this->_M_impl._M_start,
-                           this->_M_impl._M_end_of_storage
-                           - this->_M_impl._M_start);
+             _M_deallocate(__old_start,
+                           this->_M_impl._M_end_of_storage - __old_start);
              this->_M_impl._M_start = __new_start;
              this->_M_impl._M_finish = __new_finish;
              this->_M_impl._M_end_of_storage = __new_start + __len;
@@ -645,6 +647,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
            }
          else
            {
+             // Make local copies of these members because the compiler thinks
+             // the allocator can alter them if 'this' is globally reachable.
+             pointer __old_start = this->_M_impl._M_start;
+             pointer __old_finish = this->_M_impl._M_finish;
+
              const size_type __len =
                _M_check_len(__n, "vector::_M_default_append");
              pointer __new_start(this->_M_allocate(__len));
@@ -660,7 +667,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                      _M_deallocate(__new_start, __len);
                      __throw_exception_again;
                    }
-                 _S_relocate(this->_M_impl._M_start, this->_M_impl._M_finish,
+                 _S_relocate(__old_start, __old_finish,
                              __new_start, _M_get_Tp_allocator());
                }
              else
@@ -672,7 +679,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                              __n, _M_get_Tp_allocator());
                      __destroy_from = __new_start + __size;
                      std::__uninitialized_move_if_noexcept_a(
-                             this->_M_impl._M_start, this->_M_impl._M_finish,
+                             __old_start, __old_finish,
                              __new_start, _M_get_Tp_allocator());
                    }
                  __catch(...)
@@ -683,13 +690,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                      _M_deallocate(__new_start, __len);
                      __throw_exception_again;
                    }
-                 std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
+                 std::_Destroy(__old_start, __old_finish,
                                _M_get_Tp_allocator());
                }
              _GLIBCXX_ASAN_ANNOTATE_REINIT;
-             _M_deallocate(this->_M_impl._M_start,
-                           this->_M_impl._M_end_of_storage
-                           - this->_M_impl._M_start);
+             _M_deallocate(__old_start,
+                           this->_M_impl._M_end_of_storage - __old_start);
              this->_M_impl._M_start = __new_start;
              this->_M_impl._M_finish = __new_start + __size + __n;
              this->_M_impl._M_end_of_storage = __new_start + __len;
@@ -782,6 +788,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
              }
            else
              {
+               // Make local copies of these members because the compiler
+               // thinks the allocator can alter them if 'this' is globally
+               // reachable.
+               pointer __old_start = this->_M_impl._M_start;
+               pointer __old_finish = this->_M_impl._M_finish;
+
                const size_type __len =
                  _M_check_len(__n, "vector::_M_range_insert");
                pointer __new_start(this->_M_allocate(__len));
@@ -790,7 +802,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                  {
                    __new_finish
                      = std::__uninitialized_move_if_noexcept_a
-                     (this->_M_impl._M_start, __position.base(),
+                     (__old_start, __position.base(),
                       __new_start, _M_get_Tp_allocator());
                    __new_finish
                      = std::__uninitialized_copy_a(__first, __last,
@@ -798,7 +810,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                                                    _M_get_Tp_allocator());
                    __new_finish
                      = std::__uninitialized_move_if_noexcept_a
-                     (__position.base(), this->_M_impl._M_finish,
+                     (__position.base(), __old_finish,
                       __new_finish, _M_get_Tp_allocator());
                  }
                __catch(...)
@@ -808,12 +820,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
                    _M_deallocate(__new_start, __len);
                    __throw_exception_again;
                  }
-               std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
+               std::_Destroy(__old_start, __old_finish,
                              _M_get_Tp_allocator());
                _GLIBCXX_ASAN_ANNOTATE_REINIT;
-               _M_deallocate(this->_M_impl._M_start,
-                             this->_M_impl._M_end_of_storage
-                             - this->_M_impl._M_start);
+               _M_deallocate(__old_start,
+                             this->_M_impl._M_end_of_storage - __old_start);
                this->_M_impl._M_start = __new_start;
                this->_M_impl._M_finish = __new_finish;
                this->_M_impl._M_end_of_storage = __new_start + __len;