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Command-line options

General options

• --version – Display the version number and quit.

• --help – Displays help the command line option.

• -- – End of the options, all the following parameters will be treated as input files, even if they look like options.

I/O options

• -o <file> – Output filename, without extension. Extension will be added automatically, .prg for Commodore (including LUnix/LNG), .crt for Commodore cartridges, .xex for Atari computers, .a2 for Apple, .dsk for PC-88 disk images, .tap for ZX-Spectrum tape images, .rom for MSX cartridge images, .com for CP/M executables, .nes for NES/Famicom, .bin for Atari 2600, no extension for BBC micro program file, .inf for BBC Micro file metadata, .asm for assembly output, .lbl, .nl, .fns, or .sym for label file. Default: If compiling one file with .mfk extension, the same name as the input file. Otherwise, a.

• -s – Generate also the assembly output. It is not compatible with any assembler, but it serves purely informational purpose. The file has the same nam as the output file, and the extension is .asm.

• -g – Generate also the label file. The label file contains labels with their addresses, with duplicates removed. It can be loaded into the monitor of the emulator for debugging purposes. The file has the same name as the output file. The extension and the file format are platform-dependent.

• -G <format> – The same as -g, but with the specified format:

  • -G vice – format compatible with the Vice emulator. The extension is .lbl.

  • -G nesasm – format used by the NESASM assembler. The extension is .fns.

  • -G sym – format used by the WLA DX assembler. The extension is .sym.

  • -G fceux – multi-file format used by the FCEUX emulator. The extension is .nl.

  • -G mesen – format used by the Mesen emulator. The extension is .mlb.

  • -G ld65 – a simplified version of the format used by the ld65 linker (used by CC65 and CA65). The extension is .dbg.

  • -G raw – Millfork-specific format. The extension is ‘.labels’. Each row contains bank number, start address, end address (if known), object type, and Millfork-specific object identifier.

• -fbreakpoints, -fno-breakpoints – Whether the compiler should use the breakpoint macro. When enabled, breakpoints become memory barriers and the label file will contain the breakpoints if the format supports them. Currently, the only formats that supports breakpoints are vice and sym. .ini equivalent: breakpoints. Default: yes.

• -I <dir>;<dir> – The include directories. Those directories are searched for modules and platform definitions. When searching for modules, the directory containing the file currently being compiled is also searched. When searching for platform definitions, the current working directory is also searched. If not given, the compiler will try to detect the default include directory. If given, then the compiler will NOT try to detect the default include directory, and you will have to add it to the list yourself.

• -i <dir> – Add a directory to the include directories. Unlike -I, this does not replace the default include directory and allows using directories with semicolons in their names.

• -t <platform> – Target platform. It is loaded from an .ini file found in any of the include directories. See also this document.

• -r <program> – Run given program after successful compilation. Useful for automatically launching emulators without any external scripting. The program is run with the working directory set to its own directory, and it’s passed the full path to the output file as its argument.

• -R <param> – Adds a parameter to the command line of the program run with -r. All -R options are added in order, before the output file name.

• -D <feature>=<value> – Defines a feature value for the preprocessor.

• -finput_intel_syntax, -finput_zilog_syntax – Choose syntax for assembly sources on 8080-like targets. Can be overridden by the source file itself using #pragma. .ini equivalent: input_intel_syntax. Default: Intel (true) on Intel 8080/8085, Zilog (false) otherwise.

• -foutput_intel_syntax, -foutput_zilog_syntax – Choose syntax for assembly output on 8080-like targets. .ini equivalent: output_intel_syntax. Default: Intel (true) on Intel 8080/8085, Zilog (false) otherwise.

• --syntax=intel, --syntax=zilog – sets both previous options at once

• -fline-numbers, -fno-line-numbers – Whether should show source line numbers in assembly output. Slightly slows down the compilation. Default: false.

• -fsource-in-asm, -fno-source-in-asm – Whether should show the original source in assembly output. Implies -fline-numbers. Default: false.

Verbosity options

• -q – Suppress all messages except for errors.

• -v, -vv, -vvv – Increase verbosity, various levels.

Code generation options

For all targets

• -fvariable-overlap, -fno-variable-overlap – Whether variables should overlap if their scopes do not intersect.
  Default: yes.

• -fbounds-checking, -fno-bounds-checking – Whether should insert bounds checking on array access.
  Default: no.

• -fcompact-dispatch-params, -fno-compact-dispatch-params – Whether parameter values in return dispatch statements may overlap other objects. This may cause problems if the parameter table is stored next to a hardware register that has side effects when reading.
  .ini equivalent: compact_dispatch_params. Default: yes.

• -flenient-encoding, -fno-lenient-encoding – Whether the compiler should allow for invalid characters in string/character literals that use the default encodings and replace them with alternatives. .ini equivalent: lenient_encoding. Default: yes on Apple II, no otherwise.

• -fillegals, -fno-illegals – Whether should emit illegal (undocumented) NMOS 6502, Intel 8085 or Z80 opcodes.
  .ini equivalent: emit_illegals. Default: no.

6502-related

• -fcmos-ops, -fno-cmos-ops – Whether should emit 65C02 opcodes.
  .ini equivalent: emit_cmos. Default: yes if targeting a 65C02-compatible architecture, no otherwise.

• -f65ce02-ops, -fno-65ce02-ops – Whether should emit 65CE02 opcodes.
  .ini equivalent: emit_65ce026. Default: yes if targeting 65CE02, no otherwise.

• -fhuc6280-ops, -fno-huc6280-ops – Whether should emit HuC6280 opcodes.
  .ini equivalent: emit_huc6280. Default: yes if targeting HuC6280, no otherwise.

• -fno-65816-ops, -femulation-65816-ops, -fnative-65816-ops – Which subset of 65816 instructions to support. -fnative-65816-ops is required to use any 16-bit operations. Currently, there is not much support in the compiler for the native mode. .ini equivalent: emit_65816. Default: native if targeting 65816, no otherwise.

• -fjmp-fix, -fno-jmp-fix – Whether should prevent indirect JMP bug on page boundary.
  .ini equivalent: prevent_jmp_indirect_bug. Default: no if targeting a 65C02-compatible architecture or a non-6502 architecture, yes otherwise.

• -fzp-register=[0-15], -fno-zp-register – Sets the size of the zeropage pseudoregister. Increases language features on 6502-based targets. Recommended values: 2 or 4. Values higher than 4 are pointless.
  .ini equivalent: zeropage_register. Default: 4 if targeting a 6502-based architecture, 0 otherwise.

• -fdecimal-mode, -fno-decimal-mode – Whether hardware decimal mode should be used (6502 only). If disabled, a software decimal mode will be used.
  .ini equivalent: decimal_mode. Default: no if targeting Ricoh, yes otherwise.

• -fsoftware-stack, -fno-software-stack – Use a software stack for stack variables. .ini equivalent: software_stack. Default: no.

8080/Z80-related

• -f8085-ops, -fno-8085-ops – Whether should emit Intel 8085 opcodes.
  .ini equivalent: emit_8085. Default: yes if targeting Intel 8085 architecture, no otherwise.

• -fz80-ops, -fno-z80-ops – Whether should emit Z80 opcodes.
  .ini equivalents: emit_z80 and emit_x80. Default: yes if targeting a Z80-compatible architecture, no otherwise.

• -fshadow-irq, -fno-shadow-irq – Whether the interrupt routines should make use of Z80 shadow registers. .ini equivalent: use_shadow_registers_for_irq. Default: yes on Z80, no otherwise.

• -fuse-ix-for-stack, -fuse-iy-for-stack, -fno-use-index-for-stack – Which of Z80 index registers should be used for accessing stack variables, if any. .ini equivalent: ix_stack and iy_stack. Default: IX on Z80, no otherwise.

• -fuse-ix-for-scratch, -fno-use-ix-for-scratch – Allow using the IX register for other purposes. .ini equivalent: ix_scratch. Default: no.

• -fuse-iy-for-scratch, -fno-use-iy-for-scratch – Allow using the IY register for other purposes. .ini equivalent: iy_scratch. Default: no.

8086-related

Compiling to 8086 is based on translating from a mix of 8085 and Z80 instructions to 8086. See the 8086 support disclaimer.

6809-related

• -fuse-u-for-stack, -fuse-y-for-stack Which of Z80 index registers should be used as the base pointer for accessing stack variables, if any. .ini equivalent: u_stack and y_stack. Default: none.
  Warning: Currently, picking one of those two options is required! The compiler doesn’t support accessing the stack variables via the S stack pointer register yet.

Optimization options

• -O0 – Disable all optimizations except unused global symbol removal.

• -O, -O2 … -O8 – Optimize code, various levels. For most code, anything above -O4 doesn’t improve it anymore.

• -O9 – Optimize code using superoptimizer (experimental). Computationally very expensive, decent results.

• -fhints, -fno-hints – Whether optimization hints should be used. Default: yes.

• -finline, -fno-inline – Whether should inline functions automatically. See the documentation about inlining. Computationally easy, can give decent gains. .ini equivalent: inline. Default: no

• -fipo, -fno-ipo – Whether should perform interprocedural optimization. It enables certain optimization similar to what inlining would enable, but without actual inlining. .ini equivalent: ipo. Default: no.

• -fregister-variables, -fno-register-variables – Whether should allow moving local variables into CPU registers. Default: yes.

• -foptimize-stdlib, -fno-optimize-stdlib – Whether should replace some standard library calls with constant parameters with more efficient variants. Currently affects putstrz, putpstr, strzlen, scrstrlen and pstrlen, but may affect more functions in the future. .ini equivalent: optimize_stdlib. Default: no.

• -ffunction-fallthrough, -fno-function-fallthrough – Whether should replace a tail call by simply putting one function after another. .ini equivalent: function_fallthrough. Default: yes.

• -ffunction-deduplication, -fno-function-deduplication – Whether identical functions should be merged into one function. .ini equivalent: function_deduplication. Default: yes.

• -fsubroutine-extraction, -fno-subroutine-extraction – Whether identical fragments of functions should be extracted into subroutines (experimental). Makes the code smaller. For large programs, the effect is often much bigger than -Os (use both for even better effect). May occasionally be computationally very expensive. .ini equivalent: subroutine_extraction. Default: no.

• -Os, --size – Optimize for size, sacrificing some speed (experimental).

• -Of, --fast – Optimize for speed, even if it increases the size a bit (experimental). Also enables -finline.

• -Ob, --blast-processing – Optimize for speed, even if it increases the size a lot (experimental). Also enables -finline.

• -Og, --optimize-debugging – Disables optimizations that make debugging harder. Sets -fno-optimize-stdlib, -fno-variable-overlap, -fno-register-variables, -fno-function-fallthrough, -fno-function-deduplication, -fno-subroutine-extraction automatically.

• -fdangerous-optimizations – Use dangerous optimizations (experimental). Dangerous optimizations are more likely to result in broken code. Also enables -fipo and -foptimize-stdlib automatically. .ini equivalent: dangerous_optimizations.

Note: for compatibility with versions 0.3.0 and earlier, command line options --inline, --dangerous-optimizations --fipo and --fno-ipo are still recognized, but discouraged.

Warning options

By default, the compiler emits only some of the most important warnings.

• -Wall – Enable extra warnings.

• -Wnone – Disable all warnings.

• -Wfatal – Treat warnings as errors.

You can also enable or disable warnings individually:

• -Wbuggy, -Wno-buggy – Whether should warn about code that may cause surprising behaviours or even miscompilation. Default: enabled.

• -Wdeprecation, -Wno-deprecation – Whether should warn about deprecated aliases. Default: enabled.

• -Wcomparisons, -Wno-comparisons – Whether should warn about comparisons between bytes and pointers. Default: enabled.

• -Wextra-comparisons, -Wno-extra-comparisons – Whether should warn about simplifiable unsigned integer comparisons. Default: disabled.

• -Wfallback, -Wno-fallback – Whether should warn about the use of default values by text codecs, the preprocessor, and array literals. Default: enabled.

• -Wmissing-output, -Wno-missing-output – Whether should warn about data that is missing in output files. Default: enabled.

• -Woverlapping-call, -Wno-overlapping-call – Whether should warn about calls to functions in a different, yet overlapping segment. Default: enabled.

• -Wror, -Wno-ror – Whether should warn about the ROR instruction (6502 only). Default: disabled.

• -Wuseless, -Wno-useless – Whether should warn about code that does nothing. Default: enabled.

• -Whints, -Wno-hints – Whether should warn about unsupported optimization hints. Default: enabled.