472,993 Members | 2,137 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 472,993 software developers and data experts.

Error when initializing static variables

Hi,

I have some problems using static variables which results in a core
dump. I have attached code and coredump to the end of my message.

I am trying to implement a kind of factory design. I have a base class
with several sub classes. In runtime I want to create a instance of a
sub class and assign it to a base class pointer. Nothing fancy about
that. I also want to be able in runtime to decide witch type of sub
class that is to be instantiated. Another requirement is that I want to
be able to add new sub classes without changing the existing code base.
To accomplish this I have made two classes that make up the
factory-part of the design, Maker and SpecializedMaker. Maker contains
a std::map with a key and a pointer to Maker. Then specializedMaker
contains a static variable. All this is made with templates.

The makerMap is defined first and then every sub class is able to
define the static variable registerThis and by doing so adding a key
and a factory method in makerMap. It may sound complicated, but is
quite straight forward when looking at the code.

I have tried to shorten the attached example, but it is still quite
big. Sorry for the quite long post.

I know that instantiation of static variables can be a source of
trouble, but I could not find any other good way to do this.

Using CC 5.3 on Solaris gives me a working application, but when
upgrading to CC 5.7 my applications leaves a core dump instead.

My questions are:
1) Is there a better way to do this?
2) Ip my code meet the standard (and should work)? Or was I lucky when
it ran compiled with CC 5.3?
3) I the order of initialisations of static members standardized (i.e.
is the order fixed in one translation unit)?
program terminated by signal SEGV (no mapping at the fault address)
0x00013d2c: insert+0x002c: ld [%l0 + 4], %l0
(dbx) where

=>[1]
__rwstd::__rb_tree<std::basic_string<char,std::cha r_traits<char>,std::allocator<char>
,std::pair<const std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*>,__rwstd::__select1st<std::pair<co nst std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*>,std::basic_string<char,std::char_ traits<char>,std::allocator<char> > >,std::less<std::basic_string<char,std::char_trait s<char>,std::allocator<char> > >,std::allocator<std::pair<const std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*> > >::insert(0xffbef6f8, 0x27188, 0xffbef690, 0x1, 0xff06b8c8, 0x46ad0), at 0x13d2c

[2] SpecializedMaker<A,B,int>::SpecializedMaker(0x2716 c, 0xffbef7e8,
0xffbef7e7, 0xff3de79c, 0x222b0, 0x1), at 0x13350
[3] __SLIP.INIT_A(0x0, 0xff1421a0, 0xff13e5d8, 0xff1ea8d4, 0x222b0,
0xff09bc20), at 0x1310c
[4] __STATIC_CONSTRUCTOR(0x0, 0xff13c008, 0x16b48, 0xffffffff,
0x222b0, 0x16ba4), at 0x1329c
[5] 0x16c04(0x26fac, 0xff13c008, 0x16c18, 0x0, 0x0, 0x0), at 0x16c03

------------------------------------------------------------------------------

The code looks like this:

#include <iostream>
#include <string>
#include <map>

//
// Test classes
//

class A {

public:
A() : m_val(4711) {}
int getVal() {return m_val;}
private:
int m_val;
};

class B : public A {
public:
B(int i) : m_val2(i) {}
int getVal2() { return m_val2;}
private:
int m_val2;
};
//
// Maker
//
template<class T, class U = int> class Maker
{
public:

static T* newObject(const std::string& key, U arg)
{
Maker<T, U> * factory = 0;
factory = (*m_makerMap.find(key)).second;
if (factory != 0) {
return factory->createObject(arg);
}
else {
return 0;
}
}

protected:

Maker (const std::string& key)
{
m_makerMap[const_cast<std::string&>(key)] = this;
}

virtual T* createObject(U arg) const = 0;

private:

Maker() {}
Maker(const Maker& right) {}
Maker& operator= (const Maker& right) {}

static std::map<std::string, Maker<T,U>* > m_makerMap;

};
//
// SpecializedMaker
//
template<class T, class P, class U = int> class SpecializedMaker :
public Maker <T, U>
{

public:

T* createObject (U arg) const
{
return new P(arg);
}

private:

SpecializedMaker(const std::string& key)
: Maker <T, U>(key) {}

static const SpecializedMaker<T, P, U> m_registerThis;

};

template <class T, class U>
std::map<std::string, Maker<T, U>*> Maker<T, U>::m_makerMap;

const SpecializedMaker<A, B>
SpecializedMaker<A, B>::m_registerThis("B");
//
// Main
//
int main(int argc, char** argv)
{
return 0;
}

Dec 15 '05 #1
3 5658
Diebels wrote:
Hi,

I have some problems using static variables which results in a core
dump. I have attached code and coredump to the end of my message.

I am trying to implement a kind of factory design. I have a base class
with several sub classes. In runtime I want to create a instance of a
sub class and assign it to a base class pointer. Nothing fancy about
that. I also want to be able in runtime to decide witch type of sub
class that is to be instantiated. Another requirement is that I want to
be able to add new sub classes without changing the existing code base.
To accomplish this I have made two classes that make up the
factory-part of the design, Maker and SpecializedMaker. Maker contains
a std::map with a key and a pointer to Maker. Then specializedMaker
contains a static variable. All this is made with templates.

The makerMap is defined first and then every sub class is able to
define the static variable registerThis and by doing so adding a key
and a factory method in makerMap. It may sound complicated, but is
quite straight forward when looking at the code.

I have tried to shorten the attached example, but it is still quite
big. Sorry for the quite long post.

I know that instantiation of static variables can be a source of
trouble, but I could not find any other good way to do this.

Using CC 5.3 on Solaris gives me a working application, but when
upgrading to CC 5.7 my applications leaves a core dump instead.

My questions are:
1) Is there a better way to do this?
2) Ip my code meet the standard (and should work)? Or was I lucky when
it ran compiled with CC 5.3?
3) I the order of initialisations of static members standardized (i.e.
is the order fixed in one translation unit)?
program terminated by signal SEGV (no mapping at the fault address)
0x00013d2c: insert+0x002c: ld [%l0 + 4], %l0
(dbx) where

=>[1]
__rwstd::__rb_tree<std::basic_string<char,std::cha r_traits<char>,std::allocator<char>
,std::pair<const std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*>,__rwstd::__select1st<std::pair<co nst std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*>,std::basic_string<char,std::char_ traits<char>,std::allocator<char> > >,std::less<std::basic_string<char,std::char_trait s<char>,std::allocator<char> > >,std::allocator<std::pair<const std::basic_string<char,std::char_traits<char>,std: :allocator<char> >,Maker<A,int>*> > >::insert(0xffbef6f8, 0x27188, 0xffbef690, 0x1, 0xff06b8c8, 0x46ad0), at 0x13d2c

[2] SpecializedMaker<A,B,int>::SpecializedMaker(0x2716 c, 0xffbef7e8,
0xffbef7e7, 0xff3de79c, 0x222b0, 0x1), at 0x13350
[3] __SLIP.INIT_A(0x0, 0xff1421a0, 0xff13e5d8, 0xff1ea8d4, 0x222b0,
0xff09bc20), at 0x1310c
[4] __STATIC_CONSTRUCTOR(0x0, 0xff13c008, 0x16b48, 0xffffffff,
0x222b0, 0x16ba4), at 0x1329c
[5] 0x16c04(0x26fac, 0xff13c008, 0x16c18, 0x0, 0x0, 0x0), at 0x16c03

------------------------------------------------------------------------------

The code looks like this:

#include <iostream>
#include <string>
#include <map>

//
// Test classes
//

class A {

public:
A() : m_val(4711) {}
int getVal() {return m_val;}
private:
int m_val;
};

class B : public A {
public:
B(int i) : m_val2(i) {}
int getVal2() { return m_val2;}
private:
int m_val2;
};
//
// Maker
//
template<class T, class U = int> class Maker
{
public:

static T* newObject(const std::string& key, U arg)
{
Maker<T, U> * factory = 0;
factory = (*m_makerMap.find(key)).second;
if (factory != 0) {
return factory->createObject(arg);
}
else {
return 0;
}
}

protected:

Maker (const std::string& key)
{
m_makerMap[const_cast<std::string&>(key)] = this;
}

virtual T* createObject(U arg) const = 0;

private:

Maker() {}
Maker(const Maker& right) {}
Maker& operator= (const Maker& right) {}

static std::map<std::string, Maker<T,U>* > m_makerMap;

};
//
// SpecializedMaker
//
template<class T, class P, class U = int> class SpecializedMaker :
public Maker <T, U>
{

public:

T* createObject (U arg) const
{
return new P(arg);
}

private:

SpecializedMaker(const std::string& key)
: Maker <T, U>(key) {}

static const SpecializedMaker<T, P, U> m_registerThis;

};

template <class T, class U>
std::map<std::string, Maker<T, U>*> Maker<T, U>::m_makerMap;

const SpecializedMaker<A, B>
SpecializedMaker<A, B>::m_registerThis("B");
//
// Main
//
int main(int argc, char** argv)
{
return 0;
}


Interestingly, I had a very similar issue recently. See this thread,
and particularly the posts from Nov 21 and after:

http://groups.google.com/group/comp....e6e05865ffa786

The similarity is especially acute since you are using a static
variable to register with the factory. See the cited thread for a
standard conformant solution to that problem.

One other thing I would suggest is getting rid of the static map in
Maker<> and making the class a singleton instead. This would ensure
that no "static initialization order fiasco" is in play. See this FAQ
and following:

http://www.parashift.com/c++-faq-lit...html#faq-10.12

Something like the "Meyers singleton" might be good enough (if not see
_Modern C++ Design_, ch. 6 for other options):

template<class T>
class Singleton
{
public:
static T& Instance();
private:
// Disabled functions
Singleton();
Singleton( const Singleton& );
Singleton& operator=( const Singleton& );
Singleton* operator&();
~Singleton();
};

template<class T>
T& Singleton<T>::Instance()
{
static T myObject;
return myObject;
}

typedef Singleton< SpecializedMaker<A,B> > theMaker;

void Foo()
{
std::auto_ptr<A> a( theMaker::Instance().createObject( 42 ) );
// ...
}

Cheers! --M

Dec 15 '05 #2

mlimber skrev:
One other thing I would suggest is getting rid of the static map in
Maker<> and making the class a singleton instead. This would ensure
that no "static initialization order fiasco" is in play. See this FAQ
and following:


This is exactly what I am doing right now. It seems to work, but I have
to convert some of the new code to templates and do some more testing
before I am sure this is the way to go.

Thanks!

//daniel

Dec 15 '05 #3
"Diebels" <da************@gmail.com> wrote in message
news:11*********************@g47g2000cwa.googlegro ups.com
Hi,

I have some problems using static variables which results in a core
dump. I have attached code and coredump to the end of my message.
[snip] The code looks like this:

#include <iostream>
#include <string>
#include <map>

//
// Test classes
//

class A {

public:
A() : m_val(4711) {}
int getVal() {return m_val;}
private:
int m_val;
};

class B : public A {
public:
B(int i) : m_val2(i) {}
int getVal2() { return m_val2;}
private:
int m_val2;
};
//
// Maker
//
template<class T, class U = int> class Maker
{
public:

static T* newObject(const std::string& key, U arg)
{
Maker<T, U> * factory = 0;
factory = (*m_makerMap.find(key)).second;
if (factory != 0) {
return factory->createObject(arg);
}
else {
return 0;
}
}

protected:

Maker (const std::string& key)
{
m_makerMap[const_cast<std::string&>(key)] = this;
}

virtual T* createObject(U arg) const = 0;

private:

Maker() {}
Maker(const Maker& right) {}
Maker& operator= (const Maker& right) {}

static std::map<std::string, Maker<T,U>* > m_makerMap;

};
//
// SpecializedMaker
//
template<class T, class P, class U = int> class SpecializedMaker :
public Maker <T, U>
{

public:

T* createObject (U arg) const
{
return new P(arg);
}

private:

SpecializedMaker(const std::string& key)
: Maker <T, U>(key) {}

static const SpecializedMaker<T, P, U> m_registerThis;

};

template <class T, class U>
std::map<std::string, Maker<T, U>*> Maker<T, U>::m_makerMap;
Adding

template <>
std::map<std::string, Maker<A>*> Maker<A>::m_makerMap;

here seems to solve the problem (though I don't fully understand what is
going on).

The omission of template<> from the next line is non-standard
const SpecializedMaker<A, B>
SpecializedMaker<A, B>::m_registerThis("B");
//
// Main
//
int main(int argc, char** argv)
{
return 0;
}

--
John Carson
Dec 15 '05 #4

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
by: James | last post by:
Hello Java NG, I not sure if this is the right NG for this type of question but if not please let me know which is, TIA Any way first off let me say I'm a student and this WAS last weeks lab,...
17
by: MLH | last post by:
A97 Topic: If there is a way to preserve the values assigned to global variables when an untrapped runtime error occurs? I don't think there is, but I thought I'd ask. During development, I'm...
21
by: Anthony England | last post by:
Everyone knows that global variables get re-set in an mdb when an un-handled error is encountered, but it seems that this also happens when the variable is defined as private at form-level. So...
1
by: Andreas Boehm | last post by:
Hi *.*, does the standard meanwhile define something about initializing variables by the compiler? I think, it is a side-effect of the OS used, if undefined global (static) variables are...
0
by: Adam Smith | last post by:
Are there any drawbacks to initializing static member variables for classes used in an asp.net application within application_start? My classes have arraylist like tables, which cache information...
10
by: sunil | last post by:
Hello, I am new to c# . I have some basic programming doubts. Please help me in clarifying these doubts. I want to initialize a static and readonly field with a value returned by a static...
0
by: Adamn | last post by:
Hi everybody! I'm using Visual Studio 2005 and don't know how to solve this problem. Till now, everything worked just fine, included all the necessary libs, headers and so on. But there is the...
5
by: iu2 | last post by:
Hi all, This code compiles: int func1() { return 3; } void func2()
2
by: Frostmur | last post by:
Hi !! I'm trying to convert C code to C++. This is my function: static void (*selection)(void) = NULL; static void (*pick)(GLint name) = NULL; void zprSelectionFunc(void (*f)(void))
2
isladogs
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 4 Oct 2023 starting at 18:00 UK time (6PM UTC+1) and finishing at about 19:15 (7.15PM) The start time is equivalent to 19:00 (7PM) in Central...
0
tracyyun
by: tracyyun | last post by:
Hello everyone, I have a question and would like some advice on network connectivity. I have one computer connected to my router via WiFi, but I have two other computers that I want to be able to...
2
by: giovanniandrean | last post by:
The energy model is structured as follows and uses excel sheets to give input data: 1-Utility.py contains all the functions needed to calculate the variables and other minor things (mentions...
4
NeoPa
by: NeoPa | last post by:
Hello everyone. I find myself stuck trying to find the VBA way to get Access to create a PDF of the currently-selected (and open) object (Form or Report). I know it can be done by selecting :...
0
isladogs
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 1 Nov 2023 starting at 18:00 UK time (6PM UTC) and finishing at about 19:15 (7.15PM) Please note that the UK and Europe revert to winter time on...
0
NeoPa
by: NeoPa | last post by:
Introduction For this article I'll be focusing on the Report (clsReport) class. This simply handles making the calling Form invisible until all of the Reports opened by it have been closed, when it...
0
isladogs
by: isladogs | last post by:
The next online meeting of the Access Europe User Group will be on Wednesday 6 Dec 2023 starting at 18:00 UK time (6PM UTC) and finishing at about 19:15 (7.15PM). In this month's session, Mike...
4
by: GKJR | last post by:
Does anyone have a recommendation to build a standalone application to replace an Access database? I have my bookkeeping software I developed in Access that I would like to make available to other...
3
SueHopson
by: SueHopson | last post by:
Hi All, I'm trying to create a single code (run off a button that calls the Private Sub) for our parts list report that will allow the user to filter by either/both PartVendor and PartType. On...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.