Problems with pointers

[johncp]

I have a class which declares a pointer to an String (aka Borland AnsiString).
The object ufo is OK, it is used everywhere.
no_dlls is a valid non const positive integer
If I assign passivedllpaths with new I get an exception.

Why can't I assign a pointer with new, to a pointer in a class object ?

class comps
{
public:
. . .
String* passivedllpaths ;
. . .
} ;

comps* ufo = new comps(..,..) ; //constructor takes args

//and at runtime

ufo->passivedllpaths = new String[no_dlls]; //get exception


If I declare passivedllpaths outside the class I don't get an exception

String* passivedllpaths ;
passivedllpaths = new String[no_dlls] ; //Is OK

TIA johnp

 

[ctoma2005]

Hmmm, I tried the code and didn't get any exception...What's the exception? maybe I didn't write your exact code...

 

[johncp]

Hi ctoma2005

Thanx for the reply. It is interesting that you do not
get the same problem. Hmmmmm

The exception message is:-

exception class C0000005 with message
"access violation at 0x0040B85A"
write of address 0x0003F908
proccess stopped, use step or run to continue

The exception persists each time I bug run

The CPU pane shows the above to be true
0040B85A mov[edx+0x00003F908],eax
As I recall this is an indexed move from
reg eax to loc 0x00003F908
eax contains 0x0
So nothing helpful in the CPU pane

This is the code
//-----------------------------------
//declared in graph1.h
class comps
{
public:
comps(){} ; //Required by new, ?but is a default constructor created
comps(int , int ) ; //automatic, even if the user creates a non empty constructor
String compval[NUMCOMPS][3] ; //Row, Col
String plotval[NUMPLOTS][5] ;

String* passivedllpaths ;

~comps(){} ;
} ;

//++++++++++++++++++++++++
//instantiated as object ufo in graph1.cpp
//create comps object
#ifndef UFO
#define UFO
comps* ufo = new comps(NUMCOMPS, NUMPLOTS) ; //
#endif //UFO
//----------------------------------------------------
//Comps Contructor to set up the String arrays of compvals and plotvals
comps::comps(int NUMCOMPS, int NUMPLOTS)
{
for(int j=0;j<3;j++)
{ for(int i=0;i<NUMCOMPS;i++) compval[j]= "FF" ; }
for(int j=0;j<5;j++)
{ for(int i=0;i<NUMPLOTS;i++) plotval[j]= "FF" ; }
}
//--------------------------------------------------
//this funct gathers the paths of the dlls found in the dll dir.
int checkfordlls()
{
String dllpath = ".\\dlls\\*.dll" ;
int no_dlls = 0 ;
TSearchRec current_dll ; //TSearchRec is in SysUtils
if(FindFirst(dllpath, 0x04, current_dll)==0)
{
do no_dlls++ ;
while(FindNext(current_dll)==0) ;
}
if (no_dlls == 0)
{
ShowMessage("No DLLs Found") ;
return 0 ;
}
else
{
String files = IntToStr(no_dlls);
ShowMessage(String(files + " Filters Found."));
ufo->passivedllpaths = new String[no_dlls] ; //EXCEPTION OCCURS HERE !!
FindFirst(dllpath, 0x04, current_dll) ; //resets current_dll to 1st
int i = 0 ;
do
{
*(ufo->passivedllpaths + i) = current_dll.Name ;
i++ ;
}
while(FindNext(current_dll)==0) ;
return no_dlls ;
}
}

TIA johnp

 

[johncp]

Correction ! I made a typo re the CPU pane.

0040B85A mov[edx+0x00003F908],eax
eax is 0x00DD2768
edx is 0x0

Sorry