On Monday, 18 September 2006 at 0:06, Dennis Schridde wrote:
> Hi!
>
> I think we need to have a look at lib/script/interp.c : interpRunScript()
> very
> quickly.
>
> There is this UDWORD * ip which I don't fully understand.
> It doesn't seem to be used like a pointer for a while and then it gets
> dereferenced. It also gets compared with UDWORD * pCodeEnd.
>
> Looks very weird to me. Can someone figure out what it does?
ip is a pointer to a compiled (binary) script. The comparison is to see
if the end of the script (allocated memory) has been reached.
(Note: The size of the three opcodes PUSHLOCAL, POPLOCAL and
PUSHLOCALREF should be entered into the aOpSize array and used instead
of numeric values.)
> And when doing that please remember that the dereferencing in:
> if(!RetStackRemember(CurEvent, *(ip + 2))) //Remember where to jump back
> later
> was done by Christian Ohm and _not_ in the original code...
Looking at it again I guess line 942 should be
UDWORD RetStackRemember(UDWORD EvTrigIndex, UDWORD *address)
instead of
UDWORD RetStackRemember(UDWORD EvTrigIndex, UDWORD address)
so my dereferenciation is wrong. Argh... the joys of C...
In line 332 we want the address of the next instruction, that's
(ip + 2). Then it gets confused... I'll attach a patch to unconfuse
things a bit...
Question: Did this actually work? RetStackRemember increases retStackPos
by 2, but PopRetStack just decreases it by 1.
(Note: Why is RetStackRemember mentioned in script.h? It isn't used
anywhere except in interp.c.)
> Would be nice if someone could explain it's purpose to me,
According to svn blame/log, Troman wrote (some of) that code, so he can
probably tell you where I'm wrong.
--
It is a human characteristic to love little animals, especially if
they're attractive in some way.
-- McCoy, "The Trouble with Tribbles", stardate 4525.6
Index: lib/script/interp.c
===================================================================
--- lib/script/interp.c (revision 361)
+++ lib/script/interp.c (working copy)
@@ -329,7 +329,7 @@
case OP_FUNC:
//debug( LOG_SCRIPT, "-OP_FUNC" );
//debug( LOG_SCRIPT, "OP_FUNC: remember
event %d, ip=%d", CurEvent, (ip + 2) );
- if(!RetStackRemember(CurEvent, *(ip +
2))) //Remember where to jump back later
+ if(!RetStackRemember(CurEvent, (ip +
2))) //Remember where to jump back later
{
debug( LOG_ERROR,
"interpRunScript() - RetStackRemember() failed.");
return FALSE;
@@ -930,7 +930,13 @@
/* Call stack stuff */
-static UDWORD retStack[200]; //Primitive stack
+typedef struct _retstack_type
+{
+ UDWORD event;
+ UDWORD *address;
+} RETSTACK_TYPE;
+
+static RETSTACK_TYPE retStack[100]; //Primitive stack
static SDWORD retStackPos; //Current Position, always points to the last
valid element
void retStackReset(void)
@@ -939,19 +945,18 @@
}
//Remember current script execution adress
-UDWORD RetStackRemember(UDWORD EvTrigIndex, UDWORD address)
+BOOL RetStackRemember(UDWORD EvTrigIndex, UDWORD *address)
{
//DbgMsg("To remember: %d, %d, %d", EvTrigIndex, address, retStackPos);
- if (retStackPos >= 200)
+ if (retStackPos >= 100)
{
debug( LOG_ERROR, "RetStackRemember() - return address stack is
full");
return FALSE; //Stack full
}
- retStackPos = retStackPos + 2;
- retStack[retStackPos - 1] = EvTrigIndex; //First store event
index
- retStack[retStackPos] = address; //current ip
+ retStack[++retStackPos].event = EvTrigIndex; //First store event
index
+ retStack[retStackPos].address = address;
//current ip
//debug( LOG_SCRIPT, "RetStackRemember: ip=%d, event=%d", address,
EvTrigIndex);
@@ -972,10 +977,8 @@
return FALSE;
}
- *psVal = retStack[retStackPos];
+ *psVal = retStack[retStackPos--].address;
- retStackPos = retStackPos - 1;
-
//debug( LOG_SCRIPT, "PopRetStack: val=%d", *psVal);
return TRUE;
@@ -983,5 +986,5 @@
SDWORD GetCallDepth(void)
{
- return (retStackPos + 1) / 2;
+ return (retStackPos + 1);
}
Index: lib/script/script.h
===================================================================
--- lib/script/script.h (revision 361)
+++ lib/script/script.h (working copy)
@@ -61,7 +61,7 @@
* Return stack stuff
*/
extern void retStackReset(void);
-extern UDWORD RetStackRemember(UDWORD EvTrigIndex, UDWORD address);
+extern BOOL RetStackRemember(UDWORD EvTrigIndex, UDWORD *address);
extern BOOL IsRetStackEmpty(void);
extern BOOL PopRetStack(UDWORD *psVal);
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