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
177 lines
3.1 KiB
NASM
177 lines
3.1 KiB
NASM
; The assembler's front end on its own, one line per token.
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;
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; Prints the line each token started on, what the token turned out to be, how many bytes
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; it will come to, and the token itself between brackets so that whitespace at either end
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; would show if any ever leaked in.
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;
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; WHAT A TOKEN IS is the part worth checking here rather than at the far end. A wrong
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; classification does not produce a wrong byte in an obvious place - it produces a right
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; looking program of the wrong length, with everything after it shifted, and by then the
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; only symptom is that a label points at the middle of an instruction.
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;
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; Written by Anachronaut
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#Include services.asm
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#Program
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#Base 0x2000
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start:
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SETD.0 Wanted
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INIB 0d23
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SWI osArgument
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SETD.0 Wanted
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LDA.0
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BRA nothingAsked
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SETD.0 Wanted
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CALL srcOpen
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BNQ noFile
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tokenLoop:
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CALL tokNext
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BNQ tokensDone
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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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CALL clsToken
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BNQ badToken
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; Which of the six it turned out to be. The names are four characters and a space, so
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; the columns line up without any counting.
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SETD.0 TypeNames
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SETD.2 ClsType
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LDA.2
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CALL nameOfType
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SETD.1 NamePointer
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LDD.0.1
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SWI osPrintString
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SETD.0 ClsLength
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LDA.0
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INCD.0
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LDB.0
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SWI osPrintNumber ; Sixteen bits: a string of 255 characters is 256 bytes long.
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SETD.0 OpenMark
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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 CloseMark
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SWI osPrintString
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BRI tokenLoop
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badToken:
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SETD.0 StoppedText
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SWI osPrintString
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SWI osExit
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; The name of type A, out of a table of fixed width entries so that no pointer arithmetic
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; is needed beyond a multiply by the width.
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nameOfType:
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SETD.0 TypeWidth
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LDB.0
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RSTA
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SETD.0 NameLeft
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STA.0
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SETD.2 ClsType
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LDA.2
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SETD.0 NameOffset
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CALL numZero
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nameLoop:
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SETD.2 ClsType
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LDA.2
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SETD.0 NameLeft
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LDB.0
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CCF
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SUB
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BRQ nameFound
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SETD.0 TypeWidth
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LDA.0
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SETD.0 NameOffset
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CALL numAddByte
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SETD.0 NameLeft
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LDA.0
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INCA
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STA.0
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BRI nameLoop
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nameFound:
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; The answer is left in NamePointer rather than in DP0, because a RET puts Data Pointers
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; 0 to 2 back as they were: a routine cannot hand back a pointer, only write one down.
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SETD.0 TypeNames
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SETD.1 NamePointer
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STD.0.1
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SETD.0 NamePointer
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SETD.2 NameOffset
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CALL numAdd
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RET
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tokensDone:
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SETD.0 DoneText
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SWI osPrintString
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SWI osExit
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nothingAsked:
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SETD.0 AskText
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SWI osPrintString
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SWI osExit
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noFile:
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SETD.0 NoFileText
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SWI osPrintString
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SWI osExit
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#Data
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#Base 0x1000
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Wanted:
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#Reserve 0d23
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OpenMark:
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" ["
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CloseMark:
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"]
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"
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; Six names of eleven characters each, counting the zero the assembler puts on the end of
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; every string. Written one to a line so that adding a type is adding a line.
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TypeNames:
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" keyword "
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" instr "
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" value "
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" string "
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" label: "
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" label "
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TypeWidth:
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0d11
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NameLeft:
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0x00
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NameOffset:
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0x00 0x00
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NamePointer:
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0x00 0x00
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StoppedText:
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"---- stopped: the assembler does not understand that
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"
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DoneText:
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"---- no more tokens
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"
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AskText:
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"say which file
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"
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NoFileText:
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"no such file
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"
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#Include numbers.asm
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#Include source.asm
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#Include token.asm
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#Include classify.asm
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#Include table.asm
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