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Commits
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  AnachronautandClaude Opus 5
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3449405b18 |
Give the system another page of each memory
CosmOS had 1,161 bytes of Program Memory left before the address applications load at, and Tab completion is not going to fit in that with anything to spare. So the wall moves up one page: the system keeps below 0x4FFF and 0x2FFF, and an application is based at 0x5000 and 0x3000. A PAGE IS A CHEAP THING TO GIVE IT AND AN EXPENSIVE THING TO RUN OUT OF. An application still has 44K of Program Memory before the vector table and the largest one here uses 7.5K, so what was taken from applications is space nothing has ever asked for - while what the system gained is the difference between building the next thing and counting bytes while building it. Not doubling, which was the version that would have cost application space worth minding. One page, and the same again when it is needed. Nothing in the machine knows where the wall is, so this is 34 #Base lines, one threshold in the fault handler, and the table in the CosmOS README that Tests/docs.sh reads its limits out of. The native assembler's scratch map had to move with it, and docs.sh said so before anything ran: its data reached 0x40D6 and its buffers began at 0x4000, so they were sitting on its variables. That file already carries a paragraph about the floor coming up and the map staying where it was. It has happened twice now, and been caught by a check the first time wrote. Twenty three recordings are the same runs a page higher. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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588e02aff5 |
Double CosmOS's half of the machine, and check that it fits
The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit, which is fifty one bytes short of the line, and the next thing added to it went over. GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an application says where it goes with #Base and the loader puts it there, so a CosmOS that has grown past 0x1FFF simply has the next program loaded written over the end of it. What breaks is whichever part of the shell that program happened to cover, at whatever later moment somebody uses it. It turned up here as the monitor's assemble command answering "I do not know" to valid instructions, several commands into a session, on a machine that had booted perfectly well. Both halves are doubled: applications now start at 0x4000 in Program Memory and 0x2000 in Data Memory. That is 16K of code and 8K of data for the system, against the 8775 and 2948 it uses today. Both were on the same trajectory, and moving them together means the twenty files that say #Base are edited once rather than twice. The standalone loader's loadable.asm keeps its old base: it belongs to the loader CosmOS grew out of, not to CosmOS, and its addresses answer to a different program. The unbased-segment diagnostic keeps its old base too - it exists to produce an error message that names the address, and the message is what is recorded. Tests/docs.sh now reads the two limits out of the table in the README and measures both segments against them. It reads them rather than being told them because the table is the specification, and this is the second time in this project that the thing nobody checked is the thing that rotted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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fb335681d2 |
M4: SplitBit assembles SplitBit, and then assembles itself
> load Asm.sbx
> run cosmos.asm
wrote cosmos.bin: program 7036, data 2448, labels 475
> run Asm.asm
wrote Asm.sbx: program 7533, data 4099, labels 555
Both byte for byte identical to what the host assembler builds from the
same source. The machine now builds the operating system it is running on,
and builds the thing that built it.
THE CHECK THAT MATTERS MOST IS THE THIRD ONE. A binary that matches could
still have come from an assembler wrong in some way this particular source
happens not to exercise. So Tests/native.sh boots the CosmOS that CosmOS
built and has THAT assemble CosmOS again - and the second generation is
identical to the first, down to the cycle count. It is a fixed point: the
machinery has been through itself. After this the host is a convenience
rather than a necessity.
WHAT STOOD IN THE WAY was not the assembler. It loaded, faulted at 7,780
cycles, and the fault was in CosmOS: a loaded program is staged at 0x8000
before being blitted into place, so the whole FILE has to fit in the 32,768
bytes above it. The assembler's file was 33,983, and 22K of that was
zeroed scratch buffers - because #Reserve emits what it reserves.
None of that is initialised data. It is scratch, wanted only while the
assembler runs, and while it runs everything above its own data is free.
So the buffers are a MAP now rather than declarations - Assembler/scratch.asm
writes down six addresses and the file carries none of it. 33,983 bytes
became 11,648, and the assembler could load itself.
The map has a file of its own because the reader and the label table both
need addresses out of it while neither includes the other.
The sizes are cut to the largest thing it is asked to build, and that turns
out not to be the operating system: the assembler is 555 labels and 11,648
bytes of output against CosmOS's 475 and 9,564. The hardest thing this
assembles is itself.
Also: sizing it for CosmOS meant raising the label table, and raising the
label table is what pushed the file over the staging limit. The two facts
only met because the first one was tried.
Speed, measured rather than guessed: CosmOS takes 80,168,646 cycles, which
is eighty seconds of emulated time and under a second under --fast. Most of
it is a straight walk of 475 label names, several thousand times. Sorting
or bucketing that is easy and was deliberately not written before there was
something to measure.
make run-cosmos now puts every source file on the disk, so the whole thing
can be done rather than read about.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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AnachronautandClaude Opus 5
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c5e4ec3455 |
M2: the native assembler builds applications
> 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
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AnachronautandClaude Opus 5
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dcb331c151 |
SplitBit assembles SplitBit: M1, a single file with no includes
Programs/CosmOS/Assembler/ is an assembler written in SplitBit assembly. It
runs under CosmOS, reads source off a SplitBit disk, and writes a binary back
to it with no host involved anywhere:
> run Asm.sbx hello.asm
wrote hello.bin: program 17, data 14, labels 2
THE ACCEPTANCE TEST IS THE BYTES. Tests/native.sh assembles Programs/hello.asm
both ways and compares the two files byte for byte, then runs the one the
machine built. "It ran" and "the sizes look right" both pass for a binary with
a label one byte out, which is a program that jumps into the middle of an
instruction - so the only honest test is the one SplitDisk and sbfs.asm
already work under: two implementations of one written specification, each
checking the other. The files are identical and the result prints Hello,
World! in 70 cycles.
hello.asm is the target because it is the oldest program in the repository.
The first thing this machine ever ran is now the first thing it assembles for
itself.
TWO PASSES OVER STREAMED SOURCE. The C assembler reads every token of every
file into one array; that cannot port, because cosmos.asm alone is 56,047
bytes against 64K of Data Memory. The native one streams through a 256 byte
window, twice, and keeps only the label table between the passes. Two passes
suffice because every length is known without resolving anything - an
instruction's from its shape, a value's is one, a string's is its characters
and a zero - so the first pass fixes every address and the second never needs
a fixup list. A forward reference stops being a special case and becomes the
reason there are two passes at all.
The parts, each checked before anything was built on it:
source.asm characters out of a file of any size, with a line number
token.asm tokens out of characters, one character of lookahead
classify.asm what a token is, in the C assembler's order, which IS the
language: keyword, instruction, value, string, label
labels.asm names packed in an arena, four bytes of index each
numbers.asm sixteen bit arithmetic, since sbfs.asm's cannot be reached
table.asm the instruction set, generated by the same script the
monitor's copy is, and now BOTH are checked by docs.sh
readTest.asm and tokenTest.asm check the reader and the tokenizer on their
own, recorded as cosmosSource and cosmosTokens. A wrong classification does
not produce a wrong byte somewhere obvious; it produces a right looking
program of the wrong length, so it is worth catching where it happens.
WHAT IT REFUSES: #Include, #Base, #Align, #Reserve and #Vectors are refused
by name rather than ignored. Skipping a directive would produce a file that
looked right and was the wrong length, which is the worst thing an assembler
can do.
Two traps worth recording, both already known to this project and both hit
again: CALL restores A, B and DP0-DP2, so three routines returning an answer
in A had it undone by their own return; and numStep works on DP0, so three
sites that set DP1 left a pointer that never advanced.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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