[PATCH 1/2] libstdc++: Fix return value of vector::insert_range

[Patrick Palka]

On Fri, 31 Jan 2025, Patrick Palka wrote:

> In some cases we're wrongly returning an iterator pointing to (one past)
> the last element inserted instead of to the first element inserted.
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/bits/stl_bvector.h (vector<bool>::insert_range):
> 	Consistently return an iterator pointing to the first element
> 	inserted.
> 	* include/bits/vector.tcc (vector::insert_range): Likewise.
> 	* testsuite/23_containers/vector/bool/modifiers/insert/insert_range.cc:
> 	Verify insert_range return values.
> 	* testsuite/23_containers/vector/modifiers/insert/insert_range.cc:
> 	Likewise.
> ---
>  libstdc++-v3/include/bits/stl_bvector.h        |  8 ++++----
>  libstdc++-v3/include/bits/vector.tcc           |  3 ++-
>  .../bool/modifiers/insert/insert_range.cc      | 18 ++++++++++++------
>  .../vector/modifiers/insert/insert_range.cc    | 18 ++++++++++++------
>  4 files changed, 30 insertions(+), 17 deletions(-)
> 
> diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
> index 961e4a25299..e5e4b7db5a9 100644
> --- a/libstdc++-v3/include/bits/stl_bvector.h
> +++ b/libstdc++-v3/include/bits/stl_bvector.h
> @@ -1341,9 +1341,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  		      std::copy_backward(__pos._M_const_cast(), end(),
>  					 this->_M_impl._M_finish
>  					   + difference_type(__n));
> -		      auto __i = ranges::copy(__rg, __pos._M_const_cast()).out;
> +		      ranges::copy(__rg, __pos._M_const_cast()).out;

Oops, consider this stray '.out' removed.

>  		      this->_M_impl._M_finish += difference_type(__n);
> -		      return __i;
> +		      return __pos._M_const_cast();
>  		    }
>  		  else
>  		    {
> @@ -1355,9 +1355,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>  		      iterator __i = _M_copy_aligned(__begin,
>  						     __pos._M_const_cast(),
>  						     __start);
> -		      __i = ranges::copy(__rg, __i).out;
> +		      iterator __j = ranges::copy(__rg, __i).out;
>  		      iterator __finish = std::copy(__pos._M_const_cast(),
> -						    __end, __i);
> +						    __end, __j);
>  		      this->_M_deallocate();
>  		      this->_M_impl._M_end_of_storage = __q + _S_nword(__len);
>  		      this->_M_impl._M_start = __start;
> diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc
> index 4f4c366080b..acb2f5fca1e 100644
> --- a/libstdc++-v3/include/bits/vector.tcc
> +++ b/libstdc++-v3/include/bits/vector.tcc
> @@ -984,8 +984,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>        {
>  	if (__pos == cend())
>  	  {
> +	    const auto __ins_idx = size();
>  	    append_range(std::forward<_Rg>(__rg));
> -	    return end();
> +	    return begin() + __ins_idx;
>  	  }
>  
>  	if constexpr (ranges::forward_range<_Rg>)
> diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/modifiers/insert/insert_range.cc b/libstdc++-v3/testsuite/23_containers/vector/bool/modifiers/insert/insert_range.cc
> index 4f4835746ea..5c65610667d 100644
> --- a/libstdc++-v3/testsuite/23_containers/vector/bool/modifiers/insert/insert_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/vector/bool/modifiers/insert/insert_range.cc
> @@ -35,16 +35,22 @@ do_test()
>    VERIFY( eq(v, a) );
>    v.clear();
>    v.shrink_to_fit();
> -  v.insert_range(v.begin(), Range(a, a+3));
> -  v.insert_range(v.end(), Range(a+6, a+9));
> -  v.insert_range(v.begin()+3, Range(a+3, a+6));
> +  auto it = v.insert_range(v.begin(), Range(a, a+3));
> +  VERIFY( it == v.begin() );
> +  it = v.insert_range(v.end(), Range(a+6, a+9));
> +  VERIFY( it == v.begin()+3 );
> +  it = v.insert_range(v.begin()+3, Range(a+3, a+6));
> +  VERIFY( it == v.begin()+3 );
>    VERIFY( eq(v, a) );
>    v.resize(3);
> -  v.insert_range(v.begin()+1, Range(a+4, a+9));
> -  v.insert_range(v.begin()+1, Range(a+1, a+4));
> +  it = v.insert_range(v.begin()+1, Range(a+4, a+9));
> +  VERIFY( it == v.begin()+1 );
> +  it = v.insert_range(v.begin()+1, Range(a+1, a+4));
> +  VERIFY( it == v.begin()+1 );
>    v.resize(9);
>    VERIFY( eq(v, a) );
> -  v.insert_range(v.begin(), Range(a, a));
> +  it = v.insert_range(v.begin(), Range(a, a));
> +  VERIFY( it == v.begin() );
>    VERIFY( eq(v, a) );
>  }
>  
> diff --git a/libstdc++-v3/testsuite/23_containers/vector/modifiers/insert/insert_range.cc b/libstdc++-v3/testsuite/23_containers/vector/modifiers/insert/insert_range.cc
> index 68218e94f28..59071435126 100644
> --- a/libstdc++-v3/testsuite/23_containers/vector/modifiers/insert/insert_range.cc
> +++ b/libstdc++-v3/testsuite/23_containers/vector/modifiers/insert/insert_range.cc
> @@ -39,16 +39,22 @@ do_test()
>    VERIFY( eq(v, a) );
>    v.clear();
>    v.shrink_to_fit();
> -  v.insert_range(v.begin(), Range(a, a+3));
> -  v.insert_range(v.end(), Range(a+6, a+9));
> -  v.insert_range(v.begin()+3, Range(a+3, a+6));
> +  auto it = v.insert_range(v.begin(), Range(a, a+3));
> +  VERIFY( it == v.begin() );
> +  it = v.insert_range(v.end(), Range(a+6, a+9));
> +  VERIFY( it == v.begin()+3 );
> +  it = v.insert_range(v.begin()+3, Range(a+3, a+6));
> +  VERIFY( it == v.begin()+3 );
>    VERIFY( eq(v, a) );
>    v.resize(3);
> -  v.insert_range(v.begin()+1, Range(a+4, a+9));
> -  v.insert_range(v.begin()+1, Range(a+1, a+4));
> +  it = v.insert_range(v.begin()+1, Range(a+4, a+9));
> +  VERIFY( it == v.begin()+1 );
> +  it = v.insert_range(v.begin()+1, Range(a+1, a+4));
> +  VERIFY( it == v.begin()+1 );
>    v.resize(9);
>    VERIFY( eq(v, a) );
> -  v.insert_range(v.begin() + 6, Range(a, a));
> +  it = v.insert_range(v.begin() + 6, Range(a, a));
> +  VERIFY( it == v.begin() + 6 );
>    VERIFY( eq(v, a) );
>  }
>  
> -- 
> 2.48.1.157.g3b0d05c4a7
> 
>