Function definitions
Syntax:
[segment (<segment>)] [<modifiers>] <return_type> <name> ( <params> ) [align ( <alignment> )] [@ <address>] { <body> }
[segment (<segment>)] [<modifiers>] <return_type> <name> ( <params> ) [align ( <alignment> )] [@ <address>] = <expression>
[segment (<segment>)] asm <return_type> <name> ( <params> ) @ <address> extern
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<segment>: segment name; if absent, then defaults todefault_code_segmentas defined for the platform (usuallydefault) -
<modifiers>: zero or more of the following:-
asm– the function is written in assembly, not in Millfork (obligatory forexternfunctions), see Using 6502 assembly within Millfork programs#Assembly functions or Using 8080/LR35902/Z80 assembly within Millfork programs#Assembly functions;
for 8086, see the 8086 support disclaimer. -
macro– the function is a macro, see Macros_and inlining#Macros -
inline– the function should preferably be inlined see Macros_and inlining#Inlining -
noinline– the function should never be inlined -
interrupt– the function is a hardware interrupt handler. You are not allowed to call such functions directly. The function cannot have parameters and the return type should bevoid. -
kernal_interrupt– the function is an interrupt handler called from a generic vendor-provider hardware interrupt handler. The hardware instruction handler is assumed to have preserved the CPU registers, so this function only has to preserve the zeropage pseudoregisters. An example is the Commodore 64 interrupt handler that calls the function at an address read from $314/$315. Unlike hardware handlers withinterrupt, you can treat functions withkernal_interruptlike normal functions.
On non-6502-based targets, functions marked askernal_interruptdon't differ from normal functions.
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<return_type>is a valid return type, see Types -
<params>is a comma-separated list of parameters, in formtype name. Allowed types are the same as for local variables. -
<alignment>is either a numeric literal that is a power of 2, or keywordfast. The function will be allocated at the address divisible by alignment.fastmeans different things depending on the target platform:- on 6502, it means that the function will not cross a page boundary if possible
- on Z80, it is ignored
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<address>is a constant expression that defines where in the memory the function is or will be located. -
externis a keyword than marks functions that are not defined in the current program, but are likely to be available at certain address in memory. Such functions should be marked as written in assembly and should have their parameters passed through registers. -
<body>is a newline-separated list of either Millfork or assembly statements -
<expression>is an expression. It is equivalent to a function body of form{ return <expression> }.