proc main(): void {
// A comment. The whole line, and nothing of the next.
x := 1 // ...or the tail of one.
echo x
}A comment runs from // to the end of the line, and nothing more. There is no block comment in Hive itself — inside a query body, which is SQL rather than Hive, SQL's own -- and /* */ are recognised instead.
A source file is UTF-8, and its line endings may be \n or \r\n. A byte-order mark at the start of a file is refused: save it as "UTF-8", not "UTF-8 with BOM".