linux

And the other bad smell.

func(arg,arg1,arg2);

func(arg, arg1, arg2);

some function call have space after comma, but other do not have.

MySQL/MariaDB always had coding style violations for various reasons. As a rule of thumb it was agreed to enforce coding style rules only for newly written and modified code. One of good reasons was to avoid loss of "direct" RCS history. For the very same reason I'd vote to follow that rule and avoid separate coding style fixes.

I thought there should be strict rules, force coding by rules or law.

Code must clean and clear, not just ok for running.

Running is simple, continue improve and maintain code is hard.

Can we make life easier?

Now the official MySQL has it's code style guide. a big step forward.

http://dev.mysql.com/doc/internals/en/assignment.html
http://dev.mysql.com/doc/internals/en/coding-guidelines.html

The first link is for NDB coding guidelines, and even there it says clearly that

When modifying and extending existing source files or modules, the coding style already used in that code should be followed in terms of indentations, naming conventions, etc.

and

Do not do any change to NDB code purely for the sake of changing from one formatting style to another. It just causes merge annoyances and makes patches harder to read, and we do not expect the style to ever become 100% consistent across all of the source code.

I suppose that code reviews take care of the completely new code.

Based on the quotes and the earlier comment by svoj, closing for now as "Won't fix".