Ignores some cppcheck warnings

[Xav83]

This Pull Request adds comments made so that, when using inline-suppr option, cppcheck will ignore the warnings about not using explicit keyword when a constructor has one parameter.

It addresses some of the warnings in #1759

---

Pull request checklist

Read the Contribution Guidelines for detailed information.

• Changes are described in the pull request, or an existing issue is referenced.
• The test suite compiles and runs without error.
• Code coverage is 100%. Test cases can be added by editing the test suite.
• The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header file single_include/nlohmann/json.hpp. The whole process is described here.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
• Specifically, I am aware of compilation problems with Microsoft Visual Studio (there even is an issue label for these kind of bugs). I understand that even in 2016, complete C++11 support isn't there yet. But please also understand that I do not want to drop features or uglify the code just to make Microsoft's sub-standard compiler happy. The past has shown that there are ways to express the functionality such that the code compiles with the most recent MSVC - unfortunately, this is not the main objective of the project.
• Please refrain from proposing changes that would break JSON conformance. If you propose a conformant extension of JSON to be supported by the library, please motivate this extension.
• Please do not open pull requests that address multiple issues.

[coveralls]

Coverage remained the same at 100.0% when pulling e8678d3 on Xav83:ignoreCppcheckWarnings into bde5712 on nlohmann:develop.

[nlohmann]

I honestly do not really like these changes. Instead of marking every single constructor, I would rather set the respective command-line argument to the make cppcheck target.

[Xav83]

Hi @nlohmann 😃

First of all, thanks for your interest in this Pull Request. 👍

I agree with you that this is not something really elegant.
But if someone uses cppcheck on a project including the json library, he should not have those warnings too (which is my personal objective, with the issue #1759).

There are other ways to suppress warnings in cppcheck, detailed in the manual.

We can suppress each warnings in the command line and given this line to the cppcheck users.
But the more warnings will be ignored, the less this command line will be easy to read, or to integrate in a project using the json library and cppcheck.

We can create a text file, or a xml file in which the ignored warning will be detailed and given to cppchek, so that it won't trigger them. If this solution is used, then, it should be well described in the README, to make it easy for the cppcheck users to integrate this file in their workflow(since they can integrate it from conan, or as a cmake external project, for example).

I would happily modify this PR to use another solution. 😃
But I will need you, @nlohmann , or someone else to validate which solution to integrate.

Thank you in advance 🙂

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ghost]

@Xav83 I went ahead and reviewed it

[ghost]

you may have to fix line 386

[ghost]

this is the reason why