`<array>`: CTAD and element count limit
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enhancement
- Dominant language
- C++
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Description
The pseudo code below when compiled with clang errors out.
static constexpr const std::array arr = { 49000 items };
error:
<compiler>\lib\native\include\type_traits:40:27: error: recursive template instantiation exceeded maximum depth of 1024 [clang-diagnostic-error]
40 | using type = typename _Conjunction<static_cast<bool>(_Next::value), _Next, _Rest...>::type;
| ^
<compiler>\lib\native\include\type_traits:40:27: note: in instantiation of template class 'std::_Conjunction<true, std::is_same<unsigned int, unsigned int>, ..., std::is_same<unsigned int, unsigned int>>' requested here
584 | conjunction_v<is_same<_First, _Rest>...>, "N4950 [array.cons]/2: Mandates: (is_same_v<T, U> && ...) is true.");
| ^
<compiler>\lib\native\include\array:589:43: note: in instantiation of template class 'std::_Enforce_same<unsigned int, ..., unsigned int>' requested here
589 | array(_First, _Rest...) -> array<typename _Enforce_same<_First, _Rest...>::type, 1 + sizeof...(_Rest)>;
| ^
<file>:11:35: note: while substituting deduced template arguments into function template '<deduction guide for array>' [with _First = unsigned int, _Rest = <unsigned int, ..., unsigned int>]
11 | static constexpr const std::array arr = {
|
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Research direction
Reproduce the 49,000-element CTAD case with clang, then read the std::array deduction guide and _Enforce_same in alongside _Conjunction in <type_traits>. Determine why the recursive instantiation exceeds the depth limit and verify that the case compiles without changing the required element-type checking.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100