AnachronautandClaude Opus 5
c5e4ec3455
> load Asm.sbx
> run Say.asm
wrote Say.sbx: program 46, data 93, labels 7
> load Say.sbx
> run built by the machine itself
it says: built by the machine itself
The machine assembles an application and then runs what it built. Say,
greet and Files all come out byte for byte identical to the C assembler's,
and Tests/native.sh checks all three on every run alongside the boot image
M1 already covered.
WHAT IT TOOK, and it was more than #Include and #Base:
#Include The reader is a stack of readers. The current file's whole
state goes aside - buffer and all, 292 bytes - the new one
opens, and the end of it pops the old one back. A file goes in
once; including it twice does nothing, which is what lets two
libraries depend on a third. The list is forgotten between the
passes, because the second has to walk the same tree.
#Base Cursors start there, so labels hold the addresses the program
will really have. A program that says where it goes gets the
SBEX header and a .sbx name; one that says nothing gets SPBT
and .bin. A program that bases one segment and leaves the
other unbased with content in it is refused.
#Reserve Runs of zeroes, moved over in the first pass and written in
#Align the second. How many an #Align comes to depends on where the
cursor has reached, which is why both passes keep a cursor.
#Vectors Names are read and numbered, pinned where the source pins
them, so SWI osPrintString resolves. Every application needs
this - a program that calls a service names a vector declared
in a file it includes.
THE TWO PASSES ARE NOW ONE LOOP, walked twice, with Emitting the only
difference. They have to agree about the length of every token, and the way
they stop agreeing is by being two pieces of code that drifted apart -
which is the exact shape of the bug this assembler found in the C one.
Sharing the body means there is nothing to drift. What is left is checked
anyway: the second pass compares its own totals against the first's and
refuses to write the file if they differ.
THE BUG WORTH RECORDING. The tokenizer holds one character of lookahead,
and at an #Include that character belongs to the file being put aside. It
was carried across and handed back on the way out, which is wrong: a file
runs out in the middle of whatever the tokenizer happens to be doing, so
the character arrives in the middle of a word. `start:` came back as `s`
and then `tart:` - and the result assembled into a perfectly plausible
file. The fix is to undo the read instead, so the character is simply still
there when the file is opened again and the question of when to hand it
back never arises.
Three smaller ones, all old friends: three places took the CONTENTS of a
buffer where they wanted its ADDRESS; vecTakeAuto returned its answer in A,
which a RET puts back; and pass two re-declared every vector because only
the label table was being skipped on the second walk.
sameText moved down into numbers.asm from the label table - four parts want
it now, and a reader test that includes neither labels nor tokens has to
build on its own.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
323 lines
5.9 KiB
NASM
323 lines
5.9 KiB
NASM
; The label table: the only thing that survives between the two passes.
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;
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; Names are packed end to end in an arena and each index entry holds a pointer into it,
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; rather than every entry carrying a field wide enough for the longest name. MEASURED on
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; CosmOS, which is the biggest thing this will ever be asked to assemble: 453 labels
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; averaging 11.3 characters. Packed they come to about 7,400 bytes; in 32 byte fields they
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; would come to 15,400. The arena is worth the handful of extra instructions.
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;
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; Four bytes an index entry: two saying where the name is, two saying what it resolves to.
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;
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; A name is stored WITHOUT its colon, so that a definition and a use of it compare equal
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; without either side having to know which it was looking at.
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;
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; The first pass fills this and the second only reads it. That is what makes a forward
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; reference ordinary rather than special: by the time anything is emitted, every name in
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; the program already has an address.
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;
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; Written by Anachronaut
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#Program
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; Empties the table.
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labReset:
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SETD.0 LabCount
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CALL numZero
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SETD.0 LabUsed
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CALL numZero
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SETD.0 LabArena
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SETD.1 LabNext
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STD.0.1
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SETD.0 LabIndex
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SETD.1 LabBase
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STD.0.1
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RET
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; Adds the name at DP0, meaning the address in A and B. Q is zero if it went in.
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;
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; A name already in the table is refused rather than replaced: one name may mean one place,
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; and quietly taking the second would move everything that referred to the first.
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labAdd:
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SETD.2 LabPutAddress
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STA.2
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INCD.2
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STB.2
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SETD.2 LabSubject
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STD.0.2
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CALL labFind
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BNQ labAddFresh
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SETD.0 LabTwice
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CALL labComplain
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BRI labAddNo
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labAddFresh:
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SETD.0 LabCount
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SETD.2 LabLimit
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CALL numCompare
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BNC labAddFull ; The index is as full as it goes.
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; And the arena, counting the zero that ends the name.
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SETD.1 LabSubject
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LDD.0.1
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CALL labLength
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SETD.0 LabEnd
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SETD.2 LabUsed
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CALL numSet
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SETD.0 LabEnd
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SETD.2 LabLength
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CALL numAdd
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SETD.0 LabRoom
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SETD.2 LabEnd
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CALL numCompare
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BRC labAddCrowded ; The arena is smaller than where this name would end.
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; The index entry: where the name is about to go, and what it means.
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SETD.0 LabWhich
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SETD.2 LabCount
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CALL numSet
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CALL labEntryAt
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SETD.1 LabEntry
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LDD.0.1
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SETD.1 LabNext
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LDD.1.1
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PSHD.1
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POPB
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POPA ; The low byte is on top, the way a pointer is pushed.
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STA.0
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INCD.0
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STB.0
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INCD.0
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SETD.2 LabPutAddress
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LDA.2
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STA.0
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INCD.0
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INCD.2
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LDA.2
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STA.0
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; And the name itself, into the arena.
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SETD.1 LabNext
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LDD.1.1
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SETD.2 LabSubject
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LDD.0.2
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labAddLoop:
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LDA.0
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STA.1
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BRA labAddCopied
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INCD.0
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INCD.1
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BRI labAddLoop
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labAddCopied:
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INCD.1 ; Past the zero, which was copied with the rest.
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SETD.0 LabNext
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STD.1.0
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SETD.0 LabUsed
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SETD.2 LabLength
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CALL numAdd
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SETD.0 LabCount
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CALL numStep
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RSTA
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RSTB
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CCF
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ADD
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RET
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labAddFull:
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SETD.0 LabFull
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CALL labComplain
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BRI labAddNo
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labAddCrowded:
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SETD.0 LabNoRoom
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CALL labComplain
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labAddNo:
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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; Looks up the name at DP0. Q is zero if it is there, and then LabAddress is what it means.
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;
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; A straight walk from the front. With 453 labels and a few thousand uses of them that is
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; the slowest thing the assembler does, and it is deliberately the simple version: sorting
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; the table or bucketing it on the first character are both easy later, and neither is
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; worth writing before anything has been measured.
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labFind:
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SETD.2 LabSought
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STD.0.2
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SETD.0 LabWhich
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CALL numZero
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labFindLoop:
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SETD.0 LabWhich
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SETD.2 LabCount
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CALL numCompare
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BNC labFindMissing ; Walked the whole table without a match.
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CALL labEntryAt
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SETD.1 LabEntry
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LDD.0.1
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LDA.0
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INCD.0
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LDB.0
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SETD.0 LabNamePointer
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STA.0
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INCD.0
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STB.0
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SETD.1 LabNamePointer
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LDD.0.1
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SETD.1 LabSought
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LDD.1.1
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CALL sameText
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BRQ labFindGot
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SETD.0 LabWhich
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CALL numStep
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BRI labFindLoop
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labFindGot:
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SETD.1 LabEntry
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LDD.0.1
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INCD.0
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INCD.0
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LDA.0
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INCD.0
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LDB.0
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SETD.0 LabAddress
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STA.0
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INCD.0
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STB.0
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RSTA
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RSTB
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CCF
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ADD
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RET
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labFindMissing:
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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; Where entry number LabWhich is, into LabEntry. Four bytes an entry, so the offset is the
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; number doubled twice - there being no multiply on this machine, and none needed.
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labEntryAt:
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SETD.0 LabOffset
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SETD.2 LabWhich
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CALL numSet
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SETD.0 LabOffset
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SETD.2 LabOffset
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CALL numAdd
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SETD.0 LabOffset
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SETD.2 LabOffset
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CALL numAdd
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SETD.0 LabEntry
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SETD.2 LabBase
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CALL numSet
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SETD.0 LabEntry
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SETD.2 LabOffset
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CALL numAdd
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RET
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; How long the string at DP0 is, counting the zero on the end, into LabLength.
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labLength:
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SETD.1 LabLenWalk
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STD.0.1
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SETD.0 LabLength
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CALL numZero
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labLengthLoop:
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SETD.0 LabLength
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CALL numStep
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SETD.1 LabLenWalk
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LDD.0.1
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LDA.0
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BRA labLengthDone
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SETD.0 LabLenWalk
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CALL numStep
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BRI labLengthLoop
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labLengthDone:
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RET
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labComplain:
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SWI osPrintString
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SETD.0 LabNamed
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SWI osPrintString
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SETD.0 TokText
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SWI osPrintString
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SETD.0 LabAtLine
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SWI osPrintString
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SETD.0 TokLine
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LDA.0
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INCD.0
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LDB.0
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SWI osPrintNumber
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SETD.0 LabNewLine
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SWI osPrintString
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RET
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#Data
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LabCount:
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0x00 0x00
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LabUsed:
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0x00 0x00
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LabNext:
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0x00 0x00
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LabBase:
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0x00 0x00
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LabAddress:
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0x00 0x00
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LabPutAddress:
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0x00 0x00
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LabNamePointer:
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0x00 0x00
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LabSought:
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0x00 0x00
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LabSubject:
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0x00 0x00
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LabEntry:
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0x00 0x00
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LabOffset:
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0x00 0x00
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LabWhich:
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0x00 0x00
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LabLength:
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0x00 0x00
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LabLenWalk:
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0x00 0x00
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LabEnd:
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0x00 0x00
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; How many labels there may be, and how many bytes of name between them. Sized for a
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; single program rather than for CosmOS: raising either is changing a number here, and
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; running into one says so rather than writing past the end of the table.
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LabLimit:
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0x01 0x00
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LabRoom:
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0x08 0x00
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LabNamed:
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": "
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LabAtLine:
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", at line "
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LabNewLine:
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"
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"
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LabTwice:
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"that label is defined twice"
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LabFull:
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"too many labels"
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LabNoRoom:
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"no room left for label names"
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LabIndex:
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#Reserve 0d1024
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LabArena:
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#Reserve 0d2048
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