Compiler error in output serializer due to 'incompatible initializer'

[Neumann-A]

What is the issue you have?

Code does not compile in GA (windows-2019 using clang-cl 13.0.0). I see the following compiler error:

D:\a\AllProjects\AllProjects\b\vcpkg_installed\x64-windows-llvm-release\include\nlohmann/detail/output/serializer.hpp(814,25): error: variable 'end' with type 'auto *const' has incompatible initializer of type 'std::_Array_iterator<char, 64>'
            auto* const end = std::remove(number_buffer.begin(),
                        ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
D:\a\AllProjects\AllProjects\b\vcpkg_installed\x64-windows-llvm-release\include\nlohmann/detail/output/serializer.hpp(824,25): error: variable 'dec_pos' with type 'auto *const' has incompatible initializer of type 'std::_Array_iterator<char, 64>'
            auto* const dec_pos = std::find(number_buffer.begin(), number_buffer.end(), decimal_point);
                        ^         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning and 2 errors generated.

Which compiler and operating system are you using?

Current GA windows-2019
https://github.com/actions/virtual-environments/blob/main/images/win/Windows2019-Readme.md

• Compiler: clang-cl 13.0.0
• Operating system: Windows

Which version of the library did you use?

• latest release version 3.10.3
• other release - please state the version: 3.10.2
• the develop branch

I couldn't reproduce it locally but my setup does not completely match GA. Simply changing the auto* const to auto only will probably solve the problem.

[nlohmann]

• What did you try to compile?
• Please describe the steps to reproduce the issue. Can you provide a small but working code example?

[Neumann-A]

I deleted those points because I cannot give a satisfying answer to those.

I'll can give you a stackoverflow link with a similar problem though:
https://stackoverflow.com/questions/68643140/auto-const-has-incompatible-initializer-of-type-std-array-iteratorchar-48

From that it should be clear that the current code has an invalid assumption baked in.

[nlohmann]

The problem was introduced in #2561 and was the result of "fixing" Clang-Tidy warnings.

The code has to be changed back to

const auto end = std::remove(number_buffer.begin(),
                             number_buffer.begin() + len, thousands_sep);

and

const auto dec_pos = std::find(number_buffer.begin(), number_buffer.end(), decimal_point);

[nlohmann]

I @Neumann-A I created a fix in #3082. Can you please verify this works for you?

[Neumann-A]

I can verify that const auto works because I already applied that patch/change.