Segmentation fault

[ramzi TKA]

Hi
I 'am developping a new network layer in NS-2 network simulation environment in C++. I got the following error : Segmentation fault when running the program I wrote.
I have localized the line where the error ocured:

memcpy(tstr,&myDSCH_SC_IE_,sizeof(DSCH_SC_IE));

where the tstr , myDSCH_SC_IE_ , DSCH_SC_IE are defined as follows :

Packet *p = Packet::alloc(); // Network Packet memory allocation
unsigned char* tstr = p->accessdata(); // get a pointer on the data part the packet
 
typedef struct DSCH_SC_IEType {    DSCH_SC_IEType():NextXmtMx(0),NextHoldoffExponent(0),NumScheds(0) {} ;
    unsigned NextXmtMx         :5;
    unsigned NextHoldoffExponent    :3; //~Range in AV
    unsigned NumScheds         :8; 
    } DSCH_SC_IE ; // struct defining with constructor and bitfields
DSCH_SC_IE myDSCH_SC_IE_ ;

Could someone give me some suggestions
Best regards
Ramzi

[AdrianH]

Hi
I 'am developping a new network layer in NS-2 network simulation environment in C++. I got the following error : Segmentation fault when running the program I wrote.
I have localized the line where the error ocured:

memcpy(tstr,&myDSCH_SC_IE_,sizeof(DSCH_SC_IE));

where the tstr , myDSCH_SC_IE_ , DSCH_SC_IE are defined as follows :

Packet *p = Packet::alloc(); // Network Packet memory allocation
unsigned char* tstr = p->accessdata(); // get a pointer on the data part the packet
 
typedef struct DSCH_SC_IEType {    DSCH_SC_IEType():NextXmtMx(0),NextHoldoffExponent(0),NumScheds(0) {} ;
    unsigned NextXmtMx         :5;
    unsigned NextHoldoffExponent    :3; //~Range in AV
    unsigned NumScheds         :8; 
    } DSCH_SC_IE ; // struct defining with constructor and bitfields
DSCH_SC_IE myDSCH_SC_IE_ ;

Could someone give me some suggestions
Best regards
Ramzi

Did you check the return value? Perhaps you don't have an object to copy.

Hope this helps.


Adrin

[Ganon11]

Hi
I 'am developping a new network layer in NS-2 network simulation environment in C++. I got the following error : Segmentation fault when running the program I wrote.
I have localized the line where the error ocured:

memcpy(tstr,&myDSCH_SC_IE_,sizeof(DSCH_SC_IE));

where the tstr , myDSCH_SC_IE_ , DSCH_SC_IE are defined as follows :

Packet *p = Packet::alloc(); // Network Packet memory allocation
unsigned char* tstr = p->accessdata(); // get a pointer on the data part the packet
 
typedef struct DSCH_SC_IEType {    DSCH_SC_IEType():NextXmtMx(0),NextHoldoffExponent(0),NumScheds(0) {} ;
    unsigned NextXmtMx         :5;
    unsigned NextHoldoffExponent    :3; //~Range in AV
    unsigned NumScheds         :8; 
    } DSCH_SC_IE ; // struct defining with constructor and bitfields
DSCH_SC_IE myDSCH_SC_IE_ ;

Could someone give me some suggestions
Best regards
Ramzi

I'm not sure if I completely understand the problem, but I think there is a spelling mismatche: You say typedef struct DSCH_SC_IEType, but refer to the struct as DSCH_SC_IE after the definition and in other declarations and the sizeof() call.

[ramzi TKA]

Did you check the return value? Perhaps you don't have an object to copy.

Hope this helps.


Adrin

SI I have verified that objects Packet and myDSCH_SC_IE_ already exist just before the memory copy.
Regards,
Ramzi

[ramzi TKA]

I'm not sure if I completely understand the problem, but I think there is a spelling mismatche: You say typedef struct DSCH_SC_IEType, but refer to the struct as DSCH_SC_IE after the definition and in other declarations and the sizeof() call.

As you can note DSCH_SC_IE refers to the name of the type defined usong struct DSCH_SC_IEType and the key word typedef.
Regards,
Ramzi

[AdrianH]

SI I have verified that objects Packet and myDSCH_SC_IE_ already exist just before the memory copy.
Regards,
Ramzi

Hmmm, ok, are packets always the same size? Perhaps you are copying something that is not there? Your problem may be in Packet.

I tried your code with a dummy packet and it worked fine:

struct Packet
{
    unsigned int value;
 
    Packet()
    : value(999)
    {
    }
 
    static Packet * alloc()
    {
        return new Packet();
    }
 
    unsigned char * accessdata()
    {
        return reinterpret_cast<unsigned char*>(&value);
    }
};
 
typedef struct DSCH_SC_IEType {    DSCH_SC_IEType():NextXmtMx(0),NextHoldoffExponent(  0),NumScheds(0) {} ;
    unsigned NextXmtMx         :5;
    unsigned NextHoldoffExponent    :3; //~Range in AV
    unsigned NumScheds         :8; 
    } DSCH_SC_IE ; // struct defining with constructor and bitfields
DSCH_SC_IE myDSCH_SC_IE_ ;
 
#include <memory.h>
int main()
{
    Packet *p = Packet::alloc(); // Network Packet memory allocation
    unsigned char* tstr = p->accessdata(); // get a pointer on the data part the packet
 
    memcpy(tstr,&myDSCH_SC_IE_,sizeof(DSCH_SC_IE));
    return 0;
}
 

Hope this helps.


Adrian