snark13
737c974400
- Split tests/ (libc feature tests) and examples/ (real apps); shared
app.mk in repo root, was examples/example.mk
- libc/io/* split into libc/{conio,env,errno,file,mouse,string,sys,
time,video}/ — clearer module boundaries
- New examples/mdview/: markdown viewer (Phases 1-5 + light nested
lists). Headers (H1-H4), HR, ulist/olist/quote with nesting via
leading spaces, fenced code blocks, inline emphasis (bold/italic/
underscore/code), wrap/unwrap mode with soft wrap (F2), horizontal
pan (← →) with '>' truncation indicator
- libc additions: scroll() in conio (ESTEX SCROLL), strlwr/strupr,
gets() test
- Makefile updates across tests/ for the new shared app.mk path
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
41 lines
1.5 KiB
C
41 lines
1.5 KiB
C
/*
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* _errno_set — set `errno` from an ESTEX error code (0..255 in A).
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*
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* Replaces the inline pattern
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* ld (_errno), a
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* xor a, a
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* ld (_errno+1), a ; 7 bytes per error path
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* with a single
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* call __errno_set ; 3 bytes per error path
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*
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* Saves ~4 bytes at every libc error handler that converts an ESTEX
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* code into the C-side `errno`. Helper itself is 7 bytes; with 10+
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* error paths in our libc the size win is net-positive.
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*
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* ABI:
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* in: A = ESTEX error code (0..255)
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* out: HL = A (zero-extended); errno fully overwritten so a prior
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* large value (e.g. errno = -1) can't leak its high byte.
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* clobbers: HL, AF flags. Caller must not depend on HL afterwards.
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*
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* Defensive 16-bit store — see chat 2026-06-02: if anyone ever assigns
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* errno via C (`errno = -1`), the high byte becomes 0xFF, and a partial
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* 8-bit write here would leave that 0xFF in place. Always writing the
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* full word keeps errno honest regardless of who set it last.
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*/
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void _errno_set(unsigned char code) __naked
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{
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(void)code;
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__asm
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;; __sdcccall(1): single uint8_t arg already in A.
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;; Write the two bytes separately so HL/BC/DE/IX/IY remain
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;; untouched. Only A is clobbered: it is the input register,
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;; and ABI does not require preserving it across a void call.
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ld (_errno), a ; low byte = code
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xor a, a
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ld (_errno+1), a ; high byte = 0
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ret
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__endasm;
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}
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