Fix error: "C++ style comments are not allowed in ISO C90" make compilation on MSYS2 MinGW64

[Astha47]

libxlsxwriter: Submitting Pull Requests

Pull Requests and Contributing to Libxlsxwriter

All patches and pull requests are welcome but in general you should start with
an issue tracker to describe what you intend to do before you do it.

Getting Started

1. Pull requests and new feature proposals must start with an [issue
   tracker][issues]. This serves as the focal point for the design discussion.
2. Describe what you plan to do. If there are API changes add some code
   example to demonstrate them.
3. Fork the repository.
4. Run all the tests to make sure the current code works on your system using
   make test. See the Running the Test Suite section of the docs
   for instructions.
5. Create a feature branch for your new feature.

Code Style

The code style is mainly K&R style with 4 space indents.

The author uses GNU indent (gindent) 2.2.10 with the following options:

    --braces-on-if-line
    --braces-on-struct-decl-line
    --case-indentation 4
    --continue-at-parentheses
    --declaration-comment-column 0
    --format-first-column-comments
    --honour-newlines
    --ignore-profile
    --indent-label 0
    --indent-level 4
    --no-space-after-function-call-names
    --no-tabs
    --swallow-optional-blank-lines

The indent configuration file is available in the repo. The code
can be indented automatically if the same version of gindent is used with
the following make command:

    make indent

Note, make sure you have backed up your files or added them to the index
before running this command.

In general follow the existing style in the code.

Writing and Running Tests

Any significant features should be accompanied by a test. See the test
directory and the Running the Test Suite section of the docs for
details of the test setup.

The tests can be run as follows:

    make test

Same as:

    make test_unit
    make test_functional

The functional tests require the Python module pytest as a test runner.

If you have valgrind installed you can use the test suite to check for memory leaks:

    make test_valgrind

When you push your changes they will also be tested automatically using
GitHub Actions.

Documentation

The libxlsxwriter documentation is written in Doxygen format in the header
files and in additional .dox files in the docs/src directory of the
repo. The documentation can be built as follows:

    make docs
    open docs/html/index.html

Example programs

If applicable add an example program to the examples directory. Example
files can be built using:

   make docs

Copyright and License

Copyright remains with the original author. Do not include additional
copyright claims or Licensing requirements. GitHub and the git repository
will record your contribution and it will be acknowledged it in the Changes
file.

Submitting the Pull Request

If your change involves several incremental git commits then rebase or
squash them onto another branch so that the Pull Request is a single commit
or a small number of logical commits.

Push your changes to GitHub and submit the Pull Request with a hash link to
the to the Issue tracker that was opened above.

[jmcnamara]

Thanks for that. I flagged that this might be an issue when the the zlib files were updated recently but I couldn't reproduce it as the time:

#432 (comment)

Just to note that if you wish to submit the PR then the // comments should be change to single line /* */ comments and the changes need to be made in 2 sets of files:

./include/xlsxwriter/third_party/
./third_party/minizip/

Otherwise I can make the changes myself if you prefer.

[jmcnamara]

Fixed on main. Thanks.