On Wed, 21 May 2025, Jonathan Wakely wrote:
> Because this constructor delegates to vector(a) the object has been
> fully constructed and the destructor will run if an exception happens.
> That means we need to set _M_finish == _M_start so that the destructor
> doesn't try to destroy any elements.
LGTM (and TIL!)
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/120367
> * include/bits/stl_vector.h (_M_range_initialize): Initialize
> _M_impl._M_finish.
> * testsuite/23_containers/vector/cons/from_range.cc: Check with
> a type that throws on construction.
> exceptions during construction.
> ---
>
> Tested x86_64-linux.
>
> libstdc++-v3/include/bits/stl_vector.h | 1 +
> .../23_containers/vector/cons/from_range.cc | 22 +++++++++++++++++++
> 2 files changed, 23 insertions(+)
>
> diff --git a/libstdc++-v3/include/bits/stl_vector.h
> b/libstdc++-v3/include/bits/stl_vector.h
> index 57680b7bbcf3..43b913da778d 100644
> --- a/libstdc++-v3/include/bits/stl_vector.h
> +++ b/libstdc++-v3/include/bits/stl_vector.h
> @@ -1971,6 +1971,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
> {
> pointer __start = this->_M_impl._M_start =
> this->_M_allocate(_S_check_init_len(__n, _M_get_Tp_allocator()));
> + this->_M_impl._M_finish = __start;
> this->_M_impl._M_end_of_storage = __start + __n;
> this->_M_impl._M_finish
> = std::__uninitialized_copy_a(_GLIBCXX_MOVE(__first), __last,
> diff --git a/libstdc++-v3/testsuite/23_containers/vector/cons/from_range.cc
> b/libstdc++-v3/testsuite/23_containers/vector/cons/from_range.cc
> index 7a62645283d2..3784b9cd66ad 100644
> --- a/libstdc++-v3/testsuite/23_containers/vector/cons/from_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/vector/cons/from_range.cc
> @@ -106,8 +106,30 @@ test_constexpr()
> return true;
> }
>
> +void
> +test_pr120367()
> +{
> +#ifdef __cpp_exceptions
> + struct X
> + {
> + X(int) { throw 1; } // Cannot successfully construct an X.
> + ~X() { VERIFY(false); } // So should never need to destroy one.
> + };
> +
> + try
> + {
> + int i[1]{};
> + std::vector<X> v(std::from_range, i);
> + }
> + catch (int)
> + {
> + }
> +#endif
> +}
> +
> int main()
> {
> test_ranges();
> static_assert( test_constexpr() );
> + test_pr120367();
> }
> --
> 2.49.0
>
>
