Re: [PATCH v2 2/6] gdb support: add gdb::ranges::replace algorithm

[Matthieu Longo <matthieu.longo@arm.com>]

On 10/09/2026 12:08, Andrew Burgess wrote:
> Andrew Burgess <aburgess@redhat.com> writes:
> 
>> Matthieu Longo <matthieu.longo@arm.com> writes:
>>
>>> Provide a C++17-compatible replacement for the C++20 std::ranges::replace
>>> algorithm, allowing callers to use a consistent interface until GDB
>>> transitions to C++20. The helper should be removed once the C++ standard
>>> library implementation become available.
>>>
>>> https://en.cppreference.com/cpp/algorithm/ranges/replace
>>> ---
>>>  gdbsupport/array-view.h | 16 ++++++++++++++++
>>>  1 file changed, 16 insertions(+)
>>>
>>> diff --git a/gdbsupport/array-view.h b/gdbsupport/array-view.h
>>> index 8431d7f5add..f9842ecff30 100644
>>> --- a/gdbsupport/array-view.h
>>> +++ b/gdbsupport/array-view.h
>>> @@ -225,6 +225,22 @@ void copy (gdb::array_view<U> src, gdb::array_view<T> dest)
>>>      std::copy_backward (src.begin (), src.end (), dest.end ());
>>>  }
>>>  
>>> +namespace ranges {
>>> +
>>> +/* Replace all occurrences of a value in the provided range.
>>> +
>>> +   Note: this helper is a reimplementation of std::ranges::replace, only
>>> +   available from C++20 onwards, and consequently, should be replaced by
>>> +   std::ranges::replace once GDB switches to C++20.  */
>>> +
>>> +template <class Range, typename T>
>>> +void replace (Range r, const T &old_value, const T &new_value)
>>
>> Looking at the linked cppreference page, the C++20 functions take R as
>> 'Range &&r'.  Doesn't your versions create a copy of the range?  This
>> will work fine for non-owning ranges, like gdb::array_view, but will
>> mean replace operates on a copy of the range for something like
>> std::vector.  Even if what you have above is intentional, I think this
>> difference should be highlighted and explained.
>>
>> Also, as this isn't specifically tied to gdb::array_view, I wonder if
>> this would be better put into a new file gdbsupport/ranges.h ? I don't
>> think anything much is needed to create the new file other than just
>> adding the file, so that should be pretty easy to do.
> 
> Just as I hit send I realised that I should also say this would benefit
> from some unittests, see gdb/unittests/ for examples.
> 
> Thanks,
> Andrew

Added the unit tests in the next revision.

Matthieu