# SAS/C

## Setup

* Hunt down SAS/C 6.50, and the patches necessary to bring it up to 6.58.
* Install/extract it to your hard drive.
* Edit `S:User-Startup`:

```
; BEGIN SAS/C
ASSIGN SC: PATH:To/sasc
; END SAS/C
```

### With Vamos

[[amiga:development:vamos|Vamos]]

`smake` won't work out of the box as `smake` needs `LIBS:icon.library`.

* Grab this one from Aminet: https://aminet.net/package/util/libs/IconLib_46.4
* Extract the 68000 version of `icon.library` in a `libs` folder somewhere
* Create a new `libs` volume in the `[volumes]` section of your `.vamosrc` and point at that `libs` folder

## Gotchas

* Names of things can be up to 32 characters long. This makes naming things for test suites tough.

## Data types

* Use `far` on an struct if you get link errors about data > 32768
  * The `Custom` struct seems to trigger that
* Data types
  * `uint8_t` is `unsigned char`
  * `BOOL` is `int`

## Getting the offset of a field in a struct

Handy if you don't want to hard code all the custom chip register values.

https://stackoverflow.com/a/39805594

```c
#define offsetof(s,m) &((struct s *)0)->m
```

## DIsable Ctrl-C handling

From http://amigadev.elowar.com/read/ADCD_2.1/Devices_Manual_guide/node0196.html:

```c
#ifdef LATTICE
int CXBRK(void) { return(0); }     /* Disable SAS CTRL/C handling */
int chkabort(void) { return(0); }  /* really */
#endif
```

## Link assembler built in DevPac

* Use `XDEF` to expose a label. Function labels start with `_` in SAS/C. Standard calling convention is placing items on the stack after the return value:

```asm
; wow.s

  XDEF _wow ; SAS/C function link symbol convention
  
_wow: ; wow is int wow(char what)
  MOVE.L A5,-(SP) ; preserve A5
    MOVE.L A7,A5 ; put current stack onto A5 to use as reference to args
    MOVEQ #0,D0
    MOVE.B 11(A7),D0  ; move the char into D0
  MOVE.L (SP)+,A5
  RTS ; D0 is return value
```

In SAS/C:

```c
// main,c
extern int wow(char what);

int main(void) {
  printf("%d\n", wow(30)) ; => 30
  return 0;
}
```

At the command line:

```
genam -l wow.s
sc link to main main.c wow.o
```

The more things you preserve on the stack during the parameter extraction, the farther up you'll have to look:

```asm
_InitializeCopperlist:
  MOVEM.L A0/A5,-(SP)
    MOVE.L A7,A5
    MOVE.L 12(A5),A0
    MOVE.L #$FFFFFFFE,(A0)
  MOVEM.L (SP)+,A0/A5
  RTS
```

For more details on calling convention, search https://retro-commodore.eu/files/downloads/amigamanuals-xiik.net/Applications/SAS_C_Compiler_v6.5x___Manual_ENG/SASC6V2.txt
for Communicating between Assembl.