c-indent-new-comment-line is an interactive compiled Lisp function in `cc-cmds.el'.

(c-indent-new-comment-line &optional SOFT ALLOW-AUTO-FILL)

Break line at point and indent, continuing comment or macro if within one.
If inside a comment and `comment-multi-line' is non-nil, the
indentation and line prefix are preserved (see the
`c-comment-prefix-regexp' and `c-block-comment-prefix' variables for
details). If inside a single line comment and `comment-multi-line' is
nil, a new comment of the same type is started on the next line and
indented as appropriate for comments. If inside a macro, a line
continuation backslash is inserted and aligned as appropriate, and the
new line is indented according to `c-syntactic-indentation'.

If a fill prefix is specified, it overrides all the above.