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bugfix: initialize gap buffers before using them 

I keep running into one hole in Mu's memory-safety since dropping the Linux
dependency: null pointers no longer error when dereferenced. Here the problem
manifests as aliasing: lots of gap buffers share the same exact data near
address 0, because it was never initialized.
This commit is contained in:
Kartik K. Agaram 2021-04-28 22:03:58 -07:00
parent 7fa356abef
commit dcb6a21a91
2 changed files with 5 additions and 2 deletions
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5
shell/global.mu
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@ -76,8 +76,9 @@ fn load-globals in: (addr handle cell), self: (addr global-table) {
var value-gap-buffer-ah/edx: (addr handle gap-buffer) <- address value-gap-buffer-storage
allocate value-gap-buffer-ah
var value-gap-buffer/eax: (addr gap-buffer) <- lookup *value-gap-buffer-ah
initialize-gap-buffer value-gap-buffer, 0x1000/4KB
load-gap-buffer-from-stream value-gap-buffer, value-data
read-evaluate-and-stash-to-globals value-gap-buffer-ah, self
read-evaluate-and-move-to-globals value-gap-buffer-ah, self
loop
}
}
@ -154,6 +155,8 @@ fn render-globals screen: (addr screen), _self: (addr global-table), xmin: int,
var curr-input-ah/edx: (addr handle gap-buffer) <- get curr, input
var _curr-input/eax: (addr gap-buffer) <- lookup *curr-input-ah
var curr-input/ebx: (addr gap-buffer) <- copy _curr-input
compare curr-input, 0
break-if-=
var x/eax: int <- copy xmin
x, y <- render-gap-buffer-wrapping-right-then-down screen, curr-input, xmin, y, xmax, ymax, 0/no-cursor
}

2
shell/sandbox.mu
View File

@ -730,7 +730,7 @@ fn run _in-ah: (addr handle gap-buffer), out: (addr stream byte), globals: (addr
mark-lines-dirty trace
}
fn read-evaluate-and-stash-to-globals _in-ah: (addr handle gap-buffer), globals: (addr global-table) {
fn read-evaluate-and-move-to-globals _in-ah: (addr handle gap-buffer), globals: (addr global-table) {
var in-ah/eax: (addr handle gap-buffer) <- copy _in-ah
var in/eax: (addr gap-buffer) <- lookup *in-ah
var read-result-h: (handle cell)