7524 - bring back some abort messages

Our infrastructure for displaying errors is far more rudimentary in
baremetal. Many ways things can go wrong. But making the attempt seems
better than not.

I'm also making some effort to keep it easy to see what has been copied
over from the top-level, by not modifying copied code to use syntax
sugar and so on. It may not be an important enough reason to mix
notations in a single file.

baremetal/112read-byte.subx

@@ -23,7 +23,7 @@ read-byte:  # s: (addr stream byte) -> result/eax: byte
     8b/copy                         1/mod/*+disp8   6/rm32/esi    .           .             .           1/r32/ecx   4/disp8         .                 # copy *(esi+4) to ecx
     # if (f->read >= f->write) abort
     3b/compare                      0/mod/indirect  6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare ecx with *esi
-    0f 8d/jump-if->=  $read-byte:end/disp32  # TODO: abort
+    0f 8d/jump-if->=  $read-byte:abort/disp32
     # result = f->data[f->read]
     31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
     8a/copy-byte                    1/mod/*+disp8   4/rm32/sib    6/base/esi  1/index/ecx   .           0/r32/AL    0xc/disp8       .                 # copy byte at *(esi+ecx+12) to AL
@@ -38,4 +38,11 @@ $read-byte:end:
     5d/pop-to-ebp
     c3/return
 
+$read-byte:abort:
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "read-byte: empty stream" 3)  # 3=cyan
+    {
+      eb/jump loop/disp8
+    }
+    # never gets here
+
 # . . vim:nowrap:textwidth=0

baremetal/115write-byte.subx

@@ -22,7 +22,7 @@ append-byte:  # f: (addr stream byte), n: int
     8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
     # if (f->write >= f->size) abort
     3b/compare                      1/mod/*+disp8   7/rm32/edi    .           .             .           1/r32/ecx   8/disp8         .                 # compare ecx with *(edi+8)
-    7d/jump-if->=  $append-byte:end/disp8  # TODO: abort
+    7d/jump-if->=  $append-byte:abort/disp8
 $append-byte:to-stream:
     # write to stream
     # f->data[f->write] = LSB(n)
@@ -40,6 +40,13 @@ $append-byte:end:
     5d/pop-to-ebp
     c3/return
 
+$append-byte:abort:
+    (draw-text-wrapping-down-then-right-from-cursor-over-full-screen 0 "append-byte: out of space\n" 3)  # 3=cyan
+    {
+      eb/jump loop/disp8
+    }
+    # never gets here
+
 test-append-byte-single:
     # - check that append-byte writes to first byte of 'file'
     # setup

baremetal/309stream.subx

@@ -65,11 +65,11 @@ write-to-stream:  # s: (addr stream _), in: (addr byte), n: int
     8b/-> *(ebp+8) 7/r32/edi
     # var swrite/edx: int = s->write
     8b/-> *edi 2/r32/edx
-    # if (swrite + n > s->size) return
+    # if (swrite + n > s->size) abort
     8b/-> *(ebp+0x10) 1/r32/ecx
     01/add-to %ecx 2/r32/edx
     3b/compare 1/r32/ecx *(edi+8)
-    0f 8f/jump-if-> $write-to-stream:end/disp32  # TODO: abort
+    0f 8f/jump-if-> $write-to-stream:abort/disp32
     # var out/edx: (addr byte) = s->data + s->write
     8d/copy-address *(edi+edx+0xc) 2/r32/edx
     # var outend/ebx: (addr byte) = out + n
@@ -97,6 +97,13 @@ $write-to-stream:end:
     5d/pop-to-ebp
     c3/return
 
+$write-to-stream:abort:
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "write-to-stream: stream full" 3)  # 3=cyan
+    {
+      eb/jump loop/disp8
+    }
+    # never gets here
+
 read-from-stream:  # s: (addr stream _), out: (addr byte), n: int
     # . prologue
     55/push-ebp
@@ -111,11 +118,11 @@ read-from-stream:  # s: (addr stream _), out: (addr byte), n: int
     8b/-> *(ebp+8) 6/r32/esi
     # var sread/edx: int = s->read
     8b/-> *(esi+4) 2/r32/edx
-    # if (sread + n > s->write) return
+    # if (sread + n > s->write) abort
     8b/-> *(ebp+0x10) 1/r32/ecx
     01/add-to %ecx 2/r32/edx
     3b/compare 1/r32/ecx *esi
-    0f 8f/jump-if-> $read-from-stream:end/disp32  # TODO: abort
+    0f 8f/jump-if-> $read-from-stream:abort/disp32
     # var in/edx: (addr byte) = s->data + s->read
     8d/copy-address *(esi+edx+0xc) 2/r32/edx
     # var inend/ebx: (addr byte) = in + n
@@ -143,6 +150,12 @@ $read-from-stream:end:
     5d/pop-to-ebp
     c3/return
 
+$read-from-stream:abort:
+    (draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0 "read-from-stream: stream empty" 3)  # 3=cyan
+    {
+      eb/jump loop/disp8
+    }
+
 stream-first:  # s: (addr stream byte) -> result/eax: byte
     # . prologue
     55/push-ebp