7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 556 insertions, 0 deletions

diff --git a/linux/crenshaw2-1.subx b/linux/crenshaw2-1.subx
new file mode 100644
index 00000000..f52c9b64
--- /dev/null
+++ b/linux/crenshaw2-1.subx
@@ -0,0 +1,556 @@
+# Port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
+# which corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
+# except that we support hex digits.
+#
+# To run:
+#   $ ./bootstrap translate init.linux [01]*.subx apps/crenshaw2-1.subx -o apps/crenshaw2-1
+#   $ echo '3'  |./bootstrap run apps/crenshaw2-1
+# Expected output:
+#   # syscall(exit, 3)
+#   bb/copy-to-ebx  3/imm32
+#   b8/copy-to-eax  1/imm32/exit
+#   cd/syscall  0x80/imm8
+#
+# To run the generated output:
+#   $ echo '3'  |./bootstrap run apps/crenshaw2-1 > z1.subx
+#   $ ./bootstrap translate init.linux z1.subx -o z1
+#   $ ./bootstrap run z1
+#   $ echo $?
+#   3
+#
+# Stdin must contain just a single hex digit. Other input will print an error:
+#   $ echo 'xyz'  |./bootstrap run apps/crenshaw2-1
+#   Error: integer expected
+#
+# Names in this file sometimes follow Crenshaw's original rather than my usual
+# naming conventions.
+
+== code
+#   instruction                     effective address                                                   register    displacement    immediate
+# . op          subop               mod             rm32          base        index         scale       r32
+# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+
+Entry:  # run tests if necessary, call 'compile' if not
+    # . prologue
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+
+    # initialize heap
+    # . Heap = new-segment(Heap-size)
+    # . . push args
+    68/push  Heap/imm32
+    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Heap-size/disp32                  # push *Heap-size
+    # . . call
+    e8/call  new-segment/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+
+    # - if argc > 1 and argv[1] == "test", then return run_tests()
+    # if (argc <= 1) goto run-main
+    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0/disp8         1/imm32           # compare *ebp
+    7e/jump-if-<=  $run-main/disp8
+    # if (!kernel-string-equal?(argv[1], "test")) goto run-main
+    # . eax = kernel-string-equal?(argv[1], "test")
+    # . . push args
+    68/push  "test"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  kernel-string-equal?/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # . if (eax == false) goto run-main
+    3d/compare-eax-and  0/imm32/false
+    74/jump-if-=  $run-main/disp8
+    # run-tests()
+    e8/call  run-tests/disp32
+    # syscall(exit, *Num-test-failures)
+    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/ebx   Num-test-failures/disp32          # copy *Num-test-failures to ebx
+    eb/jump  $main:end/disp8
+$run-main:
+    # - otherwise read a program from stdin and emit its translation to stdout
+    # . compile(Stdin, 1/stdout, 2/stderr, ed)
+    # . . push args
+    68/push  0/imm32/exit-descriptor
+    68/push  2/imm32/stderr
+    68/push  1/imm32/stdout
+    68/push  Stdin/imm32
+    # . . call
+    e8/call  compile/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
+    # syscall(exit, 0)
+    bb/copy-to-ebx  0/imm32
+$main:end:
+    e8/call  syscall_exit/disp32
+
+# the main entry point
+compile:  # in: (addr buffered-file), out: fd or (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # . save registers
+    50/push-eax
+    51/push-ecx
+    # prime the pump
+    # . Look = get-char(in)
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
+    # . . call
+    e8/call  get-char/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # var num/ecx: (stream byte 7)
+    # Numbers can be 32 bits or 8 hex bytes long. One of them will be in 'Look', so we need space for 7 bytes.
+    # Sizing the stream just right buys us overflow-handling for free inside 'get-num'.
+    # Add 12 bytes for 'read', 'write' and 'size' fields, for a total of 19 bytes, or 0x13 in hex.
+    # The stack pointer is no longer aligned, so dump_stack() can be misleading past this point.
+    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               0x13/imm32        # subtract from esp
+    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
+    # initialize the stream
+    # . num->size = 7
+    c7          0/subop/copy        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           8/disp8         7/imm32           # copy to *(ecx+8)
+    # . clear-stream(num)
+    # . . push args
+    51/push-ecx
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # read a digit from 'in' into 'num'
+    # . get-num(in, num, err, ed)
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
+    51/push-ecx/num
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
+    # . . call
+    e8/call  get-num/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
+    # render 'num' into the following template on 'out':
+    #   bb/copy-to-ebx  _num_
+    #   b8/copy-to-eax  1/imm32/exit
+    #   cd/syscall  0x80/imm8
+    #
+    # . write(out, "bb/copy-to-ebx  ")
+    # . . push args
+    68/push  "bb/copy-to-ebx  "/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # . write-stream(out, num)
+    # . . push args
+    51/push-ecx/num
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # . write(out, Newline)
+    # . . push args
+    68/push  Newline/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # . write(out, "b8/copy-to-eax  1/imm32/exit\n")
+    # . . push args
+    68/push  "b8/copy-to-eax  1/imm32/exit\n"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # . write(out, "cd/syscall  0x80/imm8\n")
+    # . . push args
+    68/push  "cd/syscall  0x80/imm8\n"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+$compile:end:
+    # . restore registers
+    59/pop-to-ecx
+    58/pop-to-eax
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
+# Read a single digit into 'out'. Abort if there are none, or if there is no
+# space in 'out'.
+# Input comes from the global variable 'Look' (first byte) and the argument
+# 'in' (rest). We leave the next byte from 'in' into 'Look' on exit.
+get-num:  # in: (addr buffered-file), out: (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
+    # pseudocode:
+    #   if (!is-digit?(Look)) expected(ed, err, "integer")
+    #   if out->write >= out->size
+    #     write(err, "Error: too many digits in number\n")
+    #     stop(ed, 1)
+    #   out->data[out->write] = LSB(Look)
+    #   ++out->write
+    #   Look = get-char(in)
+    #
+    # registers:
+    #   in: esi
+    #   out: edi
+    #   out->write: ecx (cached copy; need to keep in sync)
+    #   out->size: edx
+    #   temporaries: eax, ebx
+    # We can't allocate Look to a register because it gets written implicitly in
+    # get-char in each iteration of the loop. (Thereby demonstrating that it's
+    # not the right interface for us. But we'll keep it just to follow Crenshaw.)
+    #
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # - if (is-digit?(Look)) expected(ed, err, "integer")
+    # . eax = is-digit?(Look)
+    # . . push args
+    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Look/disp32     .                 # push *Look
+    # . . call
+    e8/call  is-digit?/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . if (eax == false)
+    3d/compare-eax-and  0/imm32/false
+    75/jump-if-!=  $get-num:main/disp8
+    # . expected(ed, err, "integer")
+    # . . push args
+    68/push  "integer"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
+    # . . call
+    e8/call  expected/disp32  # never returns
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
+$get-num:main:
+    # - otherwise read a digit
+    # . save registers
+    50/push-eax
+    51/push-ecx
+    52/push-edx
+    53/push-ebx
+    56/push-esi
+    57/push-edi
+    # read necessary variables to registers
+    # esi = in
+    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
+    # edi = out
+    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   0xc/disp8       .                 # copy *(ebp+12) to edi
+    # ecx = out->write
+    8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
+    # edx = out->size
+    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   8/disp8         .                 # copy *(edi+8) to edx
+$get-num:loop:
+    # if (out->write >= out->size) error
+    39/compare                      3/mod/direct    2/rm32/edx    .           .             .           1/r32/ecx   .               .                 # compare edx with ecx
+    7d/jump-if-<  $get-num:stage2/disp8
+    # . error(ed, err, msg)  # TODO: show full number
+    # . . push args
+    68/push  "get-num: too many digits in number"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
+    # . . call
+    e8/call  error/disp32  # never returns
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
+$get-num:stage2:
+    # out->data[out->write] = LSB(Look)
+    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/edi  1/index/ecx   .           3/r32/ebx   0xc/disp8       .                 # copy edi+ecx+12 to ebx
+    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy *Look to eax
+    88/copy-byte                    0/mod/indirect  3/rm32/ebx    .           .             .           0/r32/AL    .               .                 # copy byte at AL to *ebx
+    # ++out->write
+    41/increment-ecx
+    # Look = get-char(in)
+    # . . push args
+    56/push-esi
+    # . . call
+    e8/call  get-char/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+$get-num:loop-end:
+    # persist necessary variables from registers
+    89/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy ecx to *edi
+$get-num:end:
+    # . restore registers
+    5f/pop-to-edi
+    5e/pop-to-esi
+    5b/pop-to-ebx
+    5a/pop-to-edx
+    59/pop-to-ecx
+    58/pop-to-eax
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
+test-get-num-reads-single-digit:
+    # - check that get-num returns first character if it's a digit
+    # This test uses exit-descriptors. Use ebp for setting up local variables.
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # clear all streams
+    # . clear-stream(_test-stream)
+    # . . push args
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream($_test-buffered-file->buffer)
+    # . . push args
+    68/push  $_test-buffered-file->buffer/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream(_test-output-stream)
+    # . . push args
+    68/push  _test-output-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream(_test-error-stream)
+    # . . push args
+    68/push  _test-error-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # initialize 'in'
+    # . write(_test-stream, "3")
+    # . . push args
+    68/push  "3"/imm32
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # initialize exit-descriptor 'ed' for the call to 'get-num' below
+    # . var ed/eax: exit-descriptor
+    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
+    89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
+    # . tailor-exit-descriptor(ed, 16)
+    # . . push args
+    68/push  0x10/imm32/nbytes-of-args-for-get-num
+    50/push-eax/ed
+    # . . call
+    e8/call  tailor-exit-descriptor/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # prime the pump
+    # . get-char(_test-buffered-file)
+    # . . push args
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  get-char/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # get-num(in, out, err, ed)
+    # . . push args
+    50/push-eax/ed
+    68/push  _test-error-stream/imm32
+    68/push  _test-output-stream/imm32
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  get-num/disp32
+    # registers except esp may be clobbered at this point
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
+    # check-ints-equal(*_test-output-stream->data, '3', msg)
+    # . . push args
+    68/push  "F - test-get-num-reads-single-digit"/imm32
+    68/push  0x33/imm32
+    b8/copy-to-eax  _test-output-stream/imm32
+    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
+    # . reclaim locals
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    5d/pop-to-ebp
+    c3/return
+
+test-get-num-aborts-on-non-digit-in-Look:
+    # - check that get-num returns first character if it's a digit
+    # This test uses exit-descriptors. Use ebp for setting up local variables.
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # clear all streams
+    # . clear-stream(_test-stream)
+    # . . push args
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream($_test-buffered-file->buffer)
+    # . . push args
+    68/push  $_test-buffered-file->buffer/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream(_test-output-stream)
+    # . . push args
+    68/push  _test-output-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # . clear-stream(_test-error-stream)
+    # . . push args
+    68/push  _test-error-stream/imm32
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # initialize 'in'
+    # . write(_test-stream, "3")
+    # . . push args
+    68/push  "3"/imm32
+    68/push  _test-stream/imm32
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # initialize exit-descriptor 'ed' for the call to 'get-num' below
+    # . var ed/eax: exit-descriptor
+    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
+    89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
+    # . tailor-exit-descriptor(ed, 16)
+    # . . push args
+    68/push  0x10/imm32/nbytes-of-args-for-get-num
+    50/push-eax/ed
+    # . . call
+    e8/call  tailor-exit-descriptor/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # *don't* prime the pump
+    # get-num(in, out, err, ed)
+    # . . push args
+    50/push-eax/ed
+    68/push  _test-error-stream/imm32
+    68/push  _test-output-stream/imm32
+    68/push  _test-buffered-file/imm32
+    # . . call
+    e8/call  get-num/disp32
+    # registers except esp may be clobbered at this point
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
+    # check that get-num tried to call exit(1)
+    # . check-ints-equal(ed->value, 2, msg)  # i.e. stop was called with value 1
+    # . . push args
+    68/push  "F - test-get-num-aborts-on-non-digit-in-Look"/imm32
+    68/push  2/imm32
+    # . . push ed->value
+    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
+    # . reclaim locals
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    5d/pop-to-ebp
+    c3/return
+
+## helpers
+
+# write(f, "Error: "+s+" expected\n") then stop(ed, 1)
+expected:  # ed: (addr exit-descriptor), f: fd or (addr stream byte), s: (addr array byte)
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # write(f, "Error: ")
+    # . . push args
+    68/push  "Error: "/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # write(f, s)
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # write(f, " expected\n")
+    # . . push args
+    68/push  " expected\n"/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
+    # . . call
+    e8/call  write/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
+    # stop(ed, 1)
+    # . . push args
+    68/push  1/imm32
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  stop/disp32
+    # should never get past this point
+$expected:dead-end:
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
+# read a byte from 'f', and save it in 'Look'
+get-char:  # f: (addr buffered-file)
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # . save registers
+    50/push-eax
+    # eax = read-byte-buffered(f)
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  read-byte-buffered/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # save eax to Look
+    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy eax to *Look
+$get-char:end:
+    # . restore registers
+    58/pop-to-eax
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
+is-digit?:  # c: int -> eax: boolean
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # eax = false
+    b8/copy-to-eax  0/imm32
+    # if (c < '0') return false
+    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x30/imm32        # compare *(ebp+8)
+    7c/jump-if-<  $is-digit?:end/disp8
+    # if (c > '9') return false
+    81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x39/imm32        # compare *(ebp+8)
+    7f/jump-if->  $is-digit?:end/disp8
+    # otherwise return true
+    b8/copy-to-eax  1/imm32
+$is-digit?:end:
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return
+
+== data
+
+Look:  # (char with some extra padding)
+    0/imm32
+
+# . . vim:nowrap:textwidth=0