From c4c30c7dc92ad8f5c00bf8facaa089b4ed9cab53 Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sat, 4 May 2019 14:20:16 -0700 Subject: 5140 - fix an out-of-bounds bug We were writing 32-bit words when we meant to write 8-bit bytes. Most of the time this doesn't matter because: * x86 is little endian, * a write to (x, x+1, x+2, x+3) is over-written by the next to (x+1, x+2, x+3, x+4), and * the 3 higher/later bytes are always 0 so no information is lost The only place this matters is if we're close to the end of the stream. --- subx/074print-int-decimal.subx | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/subx/074print-int-decimal.subx b/subx/074print-int-decimal.subx index a3e2eb9e..b7994c68 100644 --- a/subx/074print-int-decimal.subx +++ b/subx/074print-int-decimal.subx @@ -81,8 +81,8 @@ $print-int32-decimal:write-loop: 8b/copy 0/mod/indirect 3/rm32/EBX . . . 1/r32/ECX . . # ECX = *EBX # . ECX = &out->data[out->write] 8d/copy-address 1/mod/*+disp8 4/rm32/sib 3/base/EBX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EBX+ECX+12 to ECX - # . out->data[out->write] = EAX - 89/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/ECX . . # *ECX = EAX + # . out->data[out->write] = AL + 88/copy-byte 0/mod/indirect 1/rm32/ECX . . . 0/r32/AL . . # copy AL to byte at *ECX # out->write++ ff 0/subop/increment 0/mod/indirect 3/rm32/EBX . . . . . . # increment *EBX eb/jump $print-int32-decimal:write-loop/disp8 -- cgit 1.4.1-2-gfad0