millfork/docs/lang/preprocessor.md

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Preprocessor

The Millfork preprocessor does 2 things:

• filters lines in the input file according to current target's features

• injects the target's feature values as constants into the current file

Despite its similarity to the C preprocessor, it's much more restricted in its power:

• no file inclusion

• no macros

• separate namespaces for the preprocessor and the language (you need to use #use to use a preprocessor constant in the code)

Defining feature values

Feature values are defined in the [define] section of the platform definition file.
Each value is a signed 64-bit integer number.

Example:

[define]
WIDESCREEN=1

You can also define feature values using the -D command line option.

Built-in features

• ARCH_6502 – 1 if compiling for 6502, 0 otherwise

• ARCH_Z80 – 1 if compiling for Z80, 0 otherwise

Commonly used features

• WIDESCREEN – 1 if the horizontal screen resolution, ignoring borders, is greater than 256, 0 otherwise

• CBM – 1 if the target is an 8-bit Commodore computer, 0 otherwise

• CBM_64 – 1 if the target is an 8-bit Commodore computer compatible with Commodore 64, 0 otherwise

• KEYBOARD – 1 if the target has a keyboard, 0 otherwise

• JOYSTICKS – the maximum number of joysticks using standard hardware configurations, may be 0

• HAS_BITMAP_MODE – 1 if the target has a display mode with every pixel addressable, 0 otherwise

Built-in preprocessor functions and operators

The defined function returns 1 if the feature is defined, 0 otherwise.
All the other functions and operators treat undefined features as if they were defined as 0.

TODO not, lo, hi, +, -, *, |, &, ^, ||, &&, <<, >>,==, !=, >, >=, <, <=

The following Millfork operators and functions are not available in the preprocessor:
+', -', *', <<', >>', :, >>>>, nonet, all the assignment operators

#if/#elseif/#else/#endif

#if <expr>
#elseif <expr>
#else
#endif

TODO

#fatal/#error/#warn/#info

#error fatal error message
#error error message
#warn warning message
#info informational message

Emits a diagnostic message.

#fatal interrupts the compilation immediately.
#error causes an error, but the compilation will continue.
#warn emits a warning. It may be treated as an error depending on compilation options.
#info emits a benign diagnostic message.

#use

Exports a feature value under its name to the parser. The parser will substitute every use of that name as a variable or constant with the numeric value of the feature. The substitution will happen only within the current file. To use such value in other files, consider this:

#use WIDESCREEN
const byte is_widescreen = WIDESCREEN