https://github.com/akkartik/mu/blob/master/068error-byte.subx
 1 # Print an error message followed by the text representation of a byte. Then exit.
 2 
 3 == code
 4 #   instruction                     effective address                                                   register    displacement    immediate
 5 # . op          subop               mod             rm32          base        index         scale       r32
 6 # . 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
 7 
 8 #? Entry:  # manual test
 9 #?     # . var ed/eax: exit-descriptor
10 #?     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
11 #?     89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
12 #?     # . configure ed to really exit()
13 #?     # . . ed->target = 0
14 #?     c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
15 #?     # . error-byte(ed, Stdout, msg, 34)
16 #?     68/push  0x34/imm32
17 #?     68/push  "abc"/imm32
18 #?     68/push  Stderr/imm32
19 #?     50/push-eax
20 #?     e8/call  error-byte/disp32
21 #?     # . syscall(exit, Num-test-failures)
22 #?     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/ebx   Num-test-failures/disp32          # copy *Num-test-failures to ebx
23 #?     e8/call  syscall_exit/disp32
24 
25 # write(out, "Error: "+msg+": "+byte) then stop(ed, 1)
26 error-byte:  # ed: (addr exit-descriptor), out: (addr buffered-file), msg: (addr array byte), n: byte
27     # . prologue
28     55/push-ebp
29     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
30     # write-buffered(out, "Error: ")
31     # . . push args
32     68/push  "Error: "/imm32
33     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
34     # . . call
35     e8/call  write-buffered/disp32
36     # . . discard args
37     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
38     # write-buffered(out, msg)
39     # . . push args
40     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
41     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
42     # . . call
43     e8/call  write-buffered/disp32
44     # . . discard args
45     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
46     # write-buffered(out, ": ")
47     # . . push args
48     68/push  ": "/imm32
49     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
50     # . . call
51     e8/call  write-buffered/disp32
52     # . . discard args
53     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
54     # write-byte-hex-buffered(out, byte)
55     # . . push args
56     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
57     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
58     # . . call
59     e8/call  write-byte-hex-buffered/disp32
60     # . . discard args
61     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
62     # write-buffered(out, Newline)
63     # . . push args
64     68/push  Newline/imm32
65     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
66     # . . call
67     e8/call  write-buffered/disp32
68     # . . discard args
69     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
70     # flush(out)
71     # . . push args
72     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
73     # . . call
74     e8/call  flush/disp32
75     # . . discard args
76     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
77     # stop(ed, 1)
78     # . . push args
79     68/push  1/imm32
80     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
81     # . . call
82     e8/call  stop/disp32
83     # should never get past this point
84 $error-byte:dead-end:
85     # . epilogue
86     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
87     5d/pop-to-ebp
88     c3/return
89 
90 # . . vim:nowrap:textwidth=0