[< back to index](../index.md) # 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) Preprocessor directives by default start with `#`. To avoid conflicts with C preprocessor (for users wishing to use it), it is also possible to replace `#` with `$$`. ### 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 The following features are defined based on the chosen CPU and compilation options: * `MILLFORK_VERSION` – defined since 0.3.4, contains the version of the compiler: for version x.y.z, the value is 10000x+100y+z * `ARCH_6502` – 1 if compiling for 6502, 0 otherwise * `ARCH_I80` – 1 if compiling for Intel 8080-like processor, 0 otherwise * `ARCH_X86` – 1 if compiling for Intel 8086-like processor, 0 otherwise * `CPU_65C02`, `CPU_65CE02`, `CPU_65816`, `CPU_HUC6280`, `CPU_8080`, `CPU_8085`, `CPU_GAMEBOY`, `CPU_Z80`, `CPU_8086` – 1 if compiling for the exact given processor, 0 otherwise * `CPU_6502` – 1 if compiling for any pre-65C02 6502-like processor, 0 otherwise * `CPUFEATURE_DECIMAL_MODE` – 1 if decimal mode is enabled, 0 otherwise * `CPUFEATURE_65C02`, `CPUFEATURE_65CE02`, `CPUFEATURE_HUC6280`, `CPUFEATURE_65816_EMULATION`, `CPUFEATURE_65816_NATIVE`, `CPUFEATURE_8080`, `CPUFEATURE_8085`, `CPUFEATURE_GAMEBOY`, `CPUFEATURE_Z80`, `CPUFEATURE_6502_ILLEGALS`, `CPUFEATURE_8085_ILLEGALS`, `CPUFEATURE_Z80_ILLEGALS` – 1 if given instruction subset is enabled, 0 otherwise * `INIT_RW_MEMORY` – 1 if the option `ram_init_segment` is defined, 0 otherwise. See [the ROM vs RAM guide](../api/rom-vs-ram.md) for more information. * `OPTIMIZE_FOR_SIZE`, `OPTIMIZE_FOR_SPEED`, `OPTIMIZE_INLINE`, `OPTIMIZE_IPO` – 1 if given optimization setting is enabled, 0 otherwise * `SYNTAX_INTEL`, `SYNTAX_ZILOG` – 1 if given assembly syntax is chosen, 0 otherwise; doesn't take this file's pragmas into account * `USES_ZPREG` – 1 if the zeropage pseudoregister is used, 0 otherwise * `ZPREG_SIZE` – size of the pseudoregister in bytes, or 0 on platforms that don't use it * `TINY_RW_MEMORY` – 1 if the main ram is 256 bytes or less, 0 otherwise * `USES_IX_STACK`, `USES_IY_STACK` – 1 if given index register is used as a base pointer for stack-allocated variables, 0 otherwise * `USES_SHADOW_REGISTERS` – 1 if interrupts preserve old registers in the shadow registers, 0 if they do it on stack * `USES_SOFTWARE_STACK` – 1 if using software stack for variables (6502-like targets only), 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_COMPAT` – 1 if the target is an 8-bit Commodore computer compatible with Commodore 64, 0 otherwise * `CBM_64_CRT` – 1 if the target is a cartridge for Commodore 64, 0 otherwise * `CBM_264` – 1 if the target is an 8-bit Commodore computer from the 264 line, 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 * `MOS_6510` – 1 if the target uses a MOS 6510-compatible processor (with an I/O port at $0000/$0001) * `CPM` – 1 if the target is CP/M, 0 otherwise * `IBM_PC` – 1 if the target is IBM PC, 0 otherwise * `MSX` – 1 if the target is MSX, 0 otherwise * `NTSC` – 1 if the target is NTSC, 0 otherwise * `PAL` – 1 if the target is PAL, 0 otherwise * `NULLPTR` – physical value of `nullptr`, default 0 ### 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. The `if` function returns its second parameter if the first parameter is defined and non-zero, and the third parameter otherwise: // prints 400: #infoeval if(1, 400, 500) // prints 500: #infoeval if(0, 400, 500) 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 #elseif #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. ### `#infoeval` #infoeval Evaluates an expression and emits the result as a diagnostic message. ### `#define` #define = Defines a new feature value or redefines a previous feature value. The feature value is visible only to the preprocessor, only when processing the current file, and only in lines preprocessed after this one. ### `#use` #use = #use // equivalent to #use = Exports a value to the parser. The parser will substitute every use of the given identifier as a variable or constant with the numeric value of the feature. #use CPU_MODEL = if(CPU_65816 | ARCH_X86, 16, 8) putstrz("Your CPU is "z) putword(CPU_MODEL) putstrz("-bit."z) The substitution will happen only within the current file. To use such value in other files, consider using a normal constant: #use WIDESCREEN const byte is_widescreen = WIDESCREEN ### `#pragma` Changes the behaviour of the parser for the current file. The change applies to the whole file, regardless of where the directive is located. * `#pragma intel_syntax` – interpret assembly using Intel syntax * `#pragma zilog_syntax` – interpret assembly using Zilog syntax