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1.8 KiB
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83 lines
1.8 KiB
Markdown
[← Home](../README.md) · [Toolchain](README.md)
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# Compiler Pragmas and Inline Stubs
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## Overview
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AmigaOS library calls use **register-based** calling conventions (arguments in D0–D7/A0–A6). C compilers need pragmas or inline stubs to generate the correct register assignments instead of stack-based calls.
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---
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## Three Mechanisms
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| Method | Compiler | How it works |
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|---|---|---|
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| **Pragmas** | SAS/C | `#pragma libcall` directive |
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| **Inline headers** | GCC | Inline asm functions in `<inline/lib.h>` |
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| **Proto headers** | All | `<proto/lib.h>` — auto-selects pragma or inline |
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---
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## Pragma Example (SAS/C)
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```c
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#pragma libcall DOSBase Open 1e 2102
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/* Translates to: LVO = -0x1E = -30
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Args: D1 = arg1 (name), D2 = arg2 (mode)
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Result: D0 */
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```
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---
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## Inline Example (GCC)
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```c
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/* inline/exec.h */
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static __inline APTR
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AllocMem(ULONG byteSize, ULONG requirements)
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{
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register APTR _res __asm("d0");
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register ULONG _byteSize __asm("d0") = byteSize;
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register ULONG _requirements __asm("d1") = requirements;
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register struct ExecBase *_SysBase __asm("a6") = SysBase;
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__asm volatile (
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"jsr -198(%%a6)"
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: "=r"(_res)
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: "r"(_byteSize), "r"(_requirements), "r"(_SysBase)
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: "d1","a0","a1","cc","memory"
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);
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return _res;
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}
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```
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---
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## Generating Pragmas/Inlines from FD Files
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```bash
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# fd2pragma (Aminet: dev/misc/fd2pragma.lha):
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fd2pragma exec_lib.fd exec_lib.sfd TO pragmas/exec_pragmas.h SPECIAL 6
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fd2pragma exec_lib.fd exec_lib.sfd TO inline/exec.h SPECIAL 70
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```
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---
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## Proto Headers
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```c
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/* proto/exec.h — portable wrapper: */
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#ifdef __SASC
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#include <pragmas/exec_pragmas.h>
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#elif defined(__GNUC__)
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#include <inline/exec.h>
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#endif
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extern struct ExecBase *SysBase;
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```
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---
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## References
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- NDK39: `pragmas/`, `inline/`, `proto/` directories
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- [fd_files.md](fd_files.md) — FD file format
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