Lpc2000

Hi all.

I suspect the GNUARM compiler to have a flaw, since the following code
doesn't work as intended:

(Header)
class A
{
    public:
        A(int x);
        int m_x;
        static A* get_a_Instance();

    private:
        static A m_a;
        static A m_b;

};
(Source)
A A::m_a(1);
A A::m_b(2);

A::A(int x)
{
    m_x = x;
}

A* A::get_a_Instance()
{
   return &m_a;
}

int main()
{
   A* temp_a = get_a_Instance();
   int x = temp_a->m_x;
}

The problem is that the constuctor doesn_t get called, causing m_x to
have a garbage value (or 0). Even if I make an object of type A first,
it doesn't work. 
Is it something I have to setup in my startup.s file?

Best Regards
Søren

Hallo Søren,

When you declare a static data member within class, you are _not_ defining 
it. ( That is, your are not allocating strage for it)
Instead you must provide a global definition for it elsewhere, outside the 
class.
This is done by redeclaring the _static_ varialbe using the scope 
resolution operator to identify the class to which it belongs.
This causes storage for the varialbe to be allocated.
(Remember, a class definition is simply a logical construct that does not 
have physical reality - not so in your program)
Try not to use statics within classes - generally
also - if this program probably would work - it's not really good code.

Hope could help

Thomas Kuschel

================
Anton Paar GmbH
Research & Development
Anton-Paar-Str. 20
8054 Graz
Austria
Tel. +43 316 257-469

lpc2000@yahoogroups.com wrote on 28.06.2005 11:22:06:

> Hi all.
> 
> I suspect the GNUARM compiler to have a flaw, since the following code
> doesn't work as intended:
> 
> (Header)
> class A
> {
>     public:
>         A(int x);
>         int m_x;
>         static A* get_a_Instance();
> 
>     private:
>         static A m_a;
>         static A m_b;
> 
> };
> (Source)
> A A::m_a(1);
> A A::m_b(2);
> 
> A::A(int x)
> {
>     m_x = x;
> }
> 
> A* A::get_a_Instance()
> {
>    return &m_a;
> }
> 
> int main()
> {
>    A* temp_a = get_a_Instance();
>    int x = temp_a->m_x;
> }
> 
> The problem is that the constuctor doesn_t get called, causing m_x to
> have a garbage value (or 0). Even if I make an object of type A first,
> it doesn't work. 
> Is it something I have to setup in my startup.s file?
> 
> Best Regards
> Søren
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 


[Non-text portions of this message have been removed]

> This is done by redeclaring the _static_ varialbe using the scope 
> resolution operator to identify the class to which it belongs.
> This causes storage for the varialbe to be allocated.

I belive I already do this? In the 2 lines just below (Source)?

> Try not to use statics within classes - generally
> also - if this program probably would work - it's not really good code.

I know that the style isn't great, but it is the best way to approach
the problem we have at hand :o)

/Søren

> > Hi all.
> > 
> > I suspect the GNUARM compiler to have a flaw, since the following code
> > doesn't work as intended:
> > 
> > (Header)
> > class A
> > {
> >     public:
> >         A(int x);
> >         int m_x;
> >         static A* get_a_Instance();
> > 
> >     private:
> >         static A m_a;
> >         static A m_b;
> > 
> > };
> > (Source)
> > A A::m_a(1);
> > A A::m_b(2);
> > 
> > A::A(int x)
> > {
> >     m_x = x;
> > }
> > 
> > A* A::get_a_Instance()
> > {
> >    return &m_a;
> > }
> > 
> > int main()
> > {
> >    A* temp_a = get_a_Instance();
> >    int x = temp_a->m_x;
> > }
> > 
> > The problem is that the constuctor doesn_t get called, causing m_x to
> > have a garbage value (or 0). Even if I make an object of type A first,
> > it doesn't work. 
> > Is it something I have to setup in my startup.s file?
> > 
> > Best Regards
> > Søren
> > 
> > 
> > 
> > 
> > 
> > 
> > Yahoo! Groups Links
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> [Non-text portions of this message have been removed]

Hi

First :
instead static member , better is use singleton that call function with static object of your class.
Second:
standard startup.s file ( example from freertos or ... ) is only for C, so you nedd add extra code to call all constructors for global (static) obiects. Check WinARM site for example.

Jaromir 

  ----- Original Message ----- 
  From: soren_t_hansen 
  To: lpc2000@yahoogroups.com 
  Sent: Tuesday, June 28, 2005 1:27 PM
  Subject: [lpc2000] Re: Problems with constructor of static member class



  > This is done by redeclaring the _static_ varialbe using the scope 
  > resolution operator to identify the class to which it belongs.
  > This causes storage for the varialbe to be allocated.

  I belive I already do this? In the 2 lines just below (Source)?

  > Try not to use statics within classes - generally
  > also - if this program probably would work - it's not really good code.

  I know that the style isn't great, but it is the best way to approach
  the problem we have at hand :o)

  /Søren

  > > Hi all.
  > > 
  > > I suspect the GNUARM compiler to have a flaw, since the following code
  > > doesn't work as intended:
  > > 
  > > (Header)
  > > class A
  > > {
  > >     public:
  > >         A(int x);
  > >         int m_x;
  > >         static A* get_a_Instance();
  > > 
  > >     private:
  > >         static A m_a;
  > >         static A m_b;
  > > 
  > > };
  > > (Source)
  > > A A::m_a(1);
  > > A A::m_b(2);
  > > 
  > > A::A(int x)
  > > {
  > >     m_x = x;
  > > }
  > > 
  > > A* A::get_a_Instance()
  > > {
  > >    return &m_a;
  > > }
  > > 
  > > int main()
  > > {
  > >    A* temp_a = get_a_Instance();
  > >    int x = temp_a->m_x;
  > > }
  > > 
  > > The problem is that the constuctor doesn_t get called, causing m_x to
  > > have a garbage value (or 0). Even if I make an object of type A first,
  > > it doesn't work. 
  > > Is it something I have to setup in my startup.s file?
  > > 
  > > Best Regards
  > > Søren
  > > 
  > > 
  > > 
  > > 
  > > 
  > > 
  > > Yahoo! Groups Links
  > > 
  > > 
  > > 
  > > 
  > > 
  > > 
  > > 
  > 
  > 
  > [Non-text portions of this message have been removed]




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[Non-text portions of this message have been removed]

--- In lpc2000@yahoogroups.com, "Jaromir" <jaromir.kajdaniak@z...> wrote:
> Hi
> 
> First :
> instead static member , better is use singleton that call function
with static object of your class.
> Second:
> standard startup.s file ( example from freertos or ... ) is only for 
> C, so you nedd add extra code to call all constructors for global 
> (static) obiects. Check WinARM site for example.


I have found and added the following code: 

		LDR 	r0, =__ctors_start__
		LDR 	r1, =__ctors_end__
ctor_loop:
		CMP 	r0, r1
		BEQ 	ctor_end
		LDR 	r2, [r0], #4
		STMFD 	sp!, {r0-r1}
		MOV 	lr, pc
		MOV 	pc, r2
		LDMFD 	sp!, {r0-r1}
		B 		ctor_loop
ctor_end:

But it doesn't do the trick yet. Is there something else I'm missing
out? I'm using the startup.s file from Keil, which is intended to be
used in C.

/Søren

Check also linker script. Are you sure that Keil support C++ ? I use GCC...

Jaromir

  > First :
  > instead static member , better is use singleton that call function
  with static object of your class.
  > Second:
  > standard startup.s file ( example from freertos or ... ) is only for 
  > C, so you nedd add extra code to call all constructors for global 
  > (static) obiects. Check WinARM site for example.


  I have found and added the following code: 

              LDR       r0, =__ctors_start__
              LDR       r1, =__ctors_end__
  ctor_loop:
              CMP       r0, r1
              BEQ       ctor_end
              LDR       r2, [r0], #4
              STMFD       sp!, {r0-r1}
              MOV       lr, pc
              MOV       pc, r2
              LDMFD       sp!, {r0-r1}
              B             ctor_loop
  ctor_end:

  But it doesn't do the trick yet. Is there something else I'm missing
  out? I'm using the startup.s file from Keil, which is intended to be
  used in C.

  /Søren


_________________________________________________________________
List sprawdzony skanerem poczty mks_vir ( http://www.mks.com.pl )


[Non-text portions of this message have been removed]

--- In lpc2000@yahoogroups.com, "Jaromir" <jaromir.kajdaniak@z...> wrote:
> Check also linker script. Are you sure that Keil support C++ ? I use
GCC...
> 

Keil doesn't support C++, but their startup file has a lot of setup
(PLL, MAM) that I use. If i use crt0.s (which I guess you do?) this
stuff isn't there.

I've added the .ctors to the linker script too, but still can't make
it work.

Maybe you can send me a copy of your startup file and your linker
script? I'm growing hairless, because of this problem :o)

/Søren

Maybe problem is, that you use non-default constructor. Static obiects IMHO should have constructors without arguments - startup code (that I use, and that I saw in previus posts) can only call default constructors.

Jaromir

  ----- Original Message ----- 
  From: soren_t_hansen 
  To: lpc2000@yahoogroups.com 
  Sent: Wednesday, June 29, 2005 10:53 AM
  Subject: [lpc2000] Re: Problems with constructor of static member class


  --- In lpc2000@yahoogroups.com, "Jaromir" <jaromir.kajdaniak@z...> wrote:
  > Check also linker script. Are you sure that Keil support C++ ? I use
  GCC...
  > 

  Keil doesn't support C++, but their startup file has a lot of setup
  (PLL, MAM) that I use. If i use crt0.s (which I guess you do?) this
  stuff isn't there.

  I've added the .ctors to the linker script too, but still can't make
  it work.

  Maybe you can send me a copy of your startup file and your linker
  script? I'm growing hairless, because of this problem :o)

  /Søren


_________________________________________________________________
List sprawdzony skanerem poczty mks_vir ( http://www.mks.com.pl )


[Non-text portions of this message have been removed]

--- In lpc2000@yahoogroups.com, "Jaromir" <jaromir.kajdaniak@z...> wrote:
> Maybe problem is, that you use non-default constructor. Static
obiects IMHO should have constructors without arguments - startup code
(that I use, and that I saw in previus posts) can only call default
constructors.

I've come a little closer, solving the problem. I've now made a small
test project which is based on the startup and linker files from a
Winarm c++ project sample. In this test, the constructors gets called
nicely with and without parameters- both for static and nonstatic objects.

Therefore my suspicion in on my makefile and the options I use in the
compilation and linking. That's what I gonna spend my day on today :o)

Thanks for the help so far - I'll come back (I hope) with the solution

Best Regards
Søren