1.7.4 #line

The #line directive allows the current line number and the apparent name of the current sourcecode filename to be changed.

Syntax:

#line line-number filename

Note that if the filename is not given, then it stays the same. The line number on the current line is one greater than the number of new-line characters (so the first line number is 1).
Examples:

#line 50 user.c

#line 23