Difference between revisions of "CSC231 No-no! and Be-Careful! situations"
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<code><pre> | <code><pre> | ||
| + | compute: | ||
| + | pushad | ||
| + | push ebx | ||
| + | mov ebx, esp | ||
| + | |||
| + | ;;; get parameters from the stack | ||
| + | |||
| + | mov ecx,[ebp+XX] ;XX is some offset | ||
| + | mov eax,[ebp+YY] ;YY is some offset | ||
| + | mov ebx,[ebp+ZZ] ;ZZ is some offset | ||
| + | .for: call doSomething ;operate on eax and ebx | ||
| + | ; on return, eax contains | ||
| + | ; result we're interested in | ||
| + | loop .for | ||
| + | |||
| + | ;;; we're done | ||
| + | pop ebx | ||
| + | popad | ||
| + | ret 3*4 | ||
| + | |||
| + | |||
| + | |||
| + | |||
| + | |||
| + | |||
</pre></code> | </pre></code> | ||
Revision as of 08:17, 10 November 2010
--D. Thiebaut 13:15, 10 November 2010 (UTC)
What's wrong with the following code?
;------------------------------------------------------------------
; function that pushes several results in the stack
;------------------------------------------------------------------
compute:
pushad
mov ecx, N ;loop some number of times
mov eax, data1 ;get some data
mov ebx, data2
.for: call doSomething ;operate on eax and ebx
; on return, eax contains
; result we're interested in
push eax ;save result in stack
loop .for
;;; we're done
popad
ret
What's tricky about the following code?
compute:
pushad
push ebx
mov ebx, esp
;;; get parameters from the stack
mov ecx,[ebp+XX] ;XX is some offset
mov eax,[ebp+YY] ;YY is some offset
mov ebx,[ebp+ZZ] ;ZZ is some offset
.for: call doSomething ;operate on eax and ebx
; on return, eax contains
; result we're interested in
loop .for
;;; we're done
pop ebx
popad
ret 3*4
