4.1 Internal Preprocessor
The assembler has an internal preprocessor. The internal processor performs the following actions.
- Adjusts and removes extra white space. It leaves one space or tab before the keywords on a line, and turns any other white space on the line into a single space.
- Removes all comments, replacing them with a single space, or an appropriate number of new lines.
- Converts character constants into the appropriate numeric value.
If you have a single character (e.g., '
b') in your source code, it will be changed to the appropriate numeric value. If you have a syntax error that occurs at the single character, the assembler will not display 'b', but instead display the first digit of the decimal equivalent.For example, if you had
.global mybuf, 'b' in your source code, the error message would say “Error: Rest of line ignored. First ignored character is '9'.” Notice the error message says '9'. This is because the 'b' was converted to its decimal equivalent 98. The assembler is actually parsing.global mybuf,98
The internal processor does not perform the following actions.
- macro preprocessing
- include file handling
- anything else you may get from your C compiler’s preprocessor
You can do include file preprocessing with the .include directive. See 5 Assembler Directives.
You can use the C compiler driver to perform other C-style preprocessing
by ensuring the input file uses a .S extension. For
additional information on the compilation driver, see the compiler user's guide relevant
for your target device.
If the first line of an input file is #NO_APP or if you use the -f option, white space and comments are not removed from the input file. Within an input file, you can ask for white space and comment removal in certain portions by putting a line that says #APP before the text that may contain white space or comments, and putting a line that says #NO_APP after this text. This feature is mainly intended to support assembly statements in compilers whose output is otherwise free of comments and white space.