as: Preprocessing

1 
1 3.1 Preprocessing
1 =================
1 
1 The 'as' internal preprocessor:
1    * adjusts and removes extra whitespace.  It leaves one space or tab
1      before the keywords on a line, and turns any other whitespace on
1      the line into a single space.
1 
1    * removes all comments, replacing them with a single space, or an
1      appropriate number of newlines.
1 
1    * converts character constants into the appropriate numeric values.
1 
1    It does not do macro processing, include file handling, or anything
1 else you may get from your C compiler's preprocessor.  You can do
11 include file processing with the '.include' directive (⇒(as))).  You can use the GNU C compiler driver to get other "CPP"
11 style preprocessing by giving the input file a '.S' suffix.  ⇒
 Options Controlling the Kind of Output (gcc info)Overall Options.
1 
1    Excess whitespace, comments, and character constants cannot be used
1 in the portions of the input text that are not preprocessed.
1 
1    If the first line of an input file is '#NO_APP' or if you use the
1 '-f' option, whitespace and comments are not removed from the input
1 file.  Within an input file, you can ask for whitespace and comment
1 removal in specific portions of the by putting a line that says '#APP'
1 before the text that may contain whitespace or comments, and putting a
1 line that says '#NO_APP' after this text.  This feature is mainly intend
1 to support 'asm' statements in compilers whose output is otherwise free
1 of comments and whitespace.
1