What A.K. said. some further information:

The extern "C" declaration forces C linkage in C++ code. C linkage
disables name-mangling and C++ specific features such as function
overloading, reference parameters, namespace or class membership, bool
type, class type parameters etc.

While C linkage is commonly used to call C code from C++, it also allows
C++ code to be called from C. A C++ function with C linkage only needs
to have a C compatible interface, the code within it may use C++
constructs and libraries. So for example you can write C wrappers for
C++ code and libraries if you wish.

Here are some detailed explanations and related gotcha's:
http://david.tribble.com/text/cdiffs.htm#C99-mangling
http://www.ddj.com/dept/cpp/184402045
http://docs.hp.com/en/2159/otherlangs.htm

A.K. wrote:
> The usually way is to either place those extern "C" braces around the
> include statements (typically used für other people's code) or to make
> the include files themselves safe für use by C++ by placing
>
>   #ifdef __cplusplus
>      extern "C" {
>   #endif
>
> on top, and
>
>   #ifdef __cplusplus
>      }
>   #endif
>
> on bottom of the include file.

Hi Thank you for the information.

Now i changed my code to something like this:

//*--------------------------------------------------------------------- 
-------
//* AT91SAM7X example application "C++"
//*
//*--------------------------------------------------------------------- 
-------

#include <stdint.h>
#include <stdio.h>


//********************* includes
#ifdef __cplusplus
     extern "C" {
#endif

#include "AT91SAM7X256.h"
#include "board_ex256.h"
#include "registers.h"
#include "lcd.h"
#include "bits.h"

#ifdef __cplusplus
     }
#endif


AT91PS_PIO    m_pPIOA  = AT91C_BASE_PIOA;
AT91PS_PIO    m_pPIOB  = AT91C_BASE_PIOB;


#define LCD_RESET_LOW     m_pPIOA->PIO_CODR   = BIT2
#define LCD_RESET_HIGH    m_pPIOA->PIO_SODR   = BIT2



//********************* external functions
extern "C" {
  void LowLevelInit(void);
  void InitPeriphery(void);

}

class Display {
public:
  Display();
  void Backlight(unsigned char state);
};

Display::Display()
{
}

void Display::Backlight(unsigned char state) {

  if(state == BKLGHT_LCD_ON)
    pPIOB->PIO_SODR   = BIT20;    // Set PB20 to HIGH
  else
    pPIOB->PIO_CODR   = BIT20;    // Set PB20 to LOW

}

void init(void) {


//*************** lowlevel init (watchdog, PLL clock, default
interrupts, etc.)

  void LowLevelInit(void);
  void InitPeriphery(void);
  void InitLCD();
  void LCDSettings();

} //init

int main(void)
{

init();
Display ds;
while(1) {

    // check button SW1
    if(!((m_pPIOB->PIO_PDSR) & BIT24)) {
        ds.Backlight(BKLGHT_LCD_ON) ;
    }

    // check button SW2
    if(!((m_pPIOB->PIO_PDSR) & BIT25)) {
        ds.Backlight(BKLGHT_LCD_OFF);
    }

  }

}

When i compile i am not getting any compile errors.

But when i flash the board it says flashing finished in 0s 203128us and
nothing happens.

I dont understand where is the problem ?

Is my way of calling the functions and initializing objects correct ?

Regards
Flying

Clifford Slocombe wrote:
> What A.K. said. some further information:
>
> The extern "C" declaration forces C linkage in C++ code. C linkage
> disables name-mangling and C++ specific features such as function
> overloading, reference parameters, namespace or class membership, bool
> type, class type parameters etc.
>
> While C linkage is commonly used to call C code from C++, it also allows
> C++ code to be called from C. A C++ function with C linkage only needs
> to have a C compatible interface, the code within it may use C++
> constructs and libraries. So for example you can write C wrappers for
> C++ code and libraries if you wish.
>
> Here are some detailed explanations and related gotcha's:
> http://david.tribble.com/text/cdiffs.htm#C99-mangling
> http://www.ddj.com/dept/cpp/184402045
> http://docs.hp.com/en/2159/otherlangs.htm

Hi thank you for the links.

I will go thru them maybe i will find some more information.

Regards
Flying

> Hi thank you for the links.
>
> I will go thru them maybe i will find some more information.
>
> Regards
> Flying

Do you have a main.bin file very small ? this file should look at least
the same size of you C only code.

Jonathan

Jonathan Dumaresq wrote:
>> Hi thank you for the links.
>>
>> I will go thru them maybe i will find some more information.
>>
>> Regards
>> Flying
>
> Do you have a main.bin file very small ? this file should look at least
> the same size of you C only code.
>
> Jonathan

Hi

I have a main.bin file it has half the size of c main.bin.

Now debugging is working but i can't understand the assembly language
instructions its showing when i set the break points.

Can you please tell me how i can check where my program is going wrong
using debugger.

I can step in and step out thru the instructions but i dont understand
the instructions it shows in the disassembly view.

Regards
Flying

Jonathan Dumaresq wrote:
>> Hi thank you for the links.
>>
>> I will go thru them maybe i will find some more information.
>>
>> Regards
>> Flying
>
> Do you have a main.bin file very small ? this file should look at least
> the same size of you C only code.
>
> Jonathan

Hi

Maybe i have a linking problem with my program.

I have one more question which linker file usually we should use RAM.ld
or ROM.ld.

Because for c++ programs i always see both .ld files.

If we use ROM.ld then we should select RUN_MODE=ROM_RUN and
VECTOR_LOCATION=VECTORS_IN_RAM in makefile is it correct?

But when i see my ROM.ld file there is a command like __FIRST_IN_RAM =
ORIGIN(DATA); is it ROM or RAM?

where we can get more description about these files?

I defined only ROM.ld. How we can make decision which mode to go for?
Does this depend on the application or its our choice?

Here is my AT91SAM7x256-ROM.ld file. Is it correct ?

/*---------------------------------------------------------------------- 
-----*/
/*-         ATMEL Microcontroller Software Support  -  ROUSSET  -
*/
/*---------------------------------------------------------------------- 
-----*/
/* The software is delivered "AS IS" without warranty or condition of
any    */
/* kind, either express, implied or statutory. This includes without
*/
/* limitation any warranty or condition with respect to merchantability
or   */
/* fitness for any particular purpose, or against the infringements of
*/
/* intellectual property rights of others.
*/
/*---------------------------------------------------------------------- 
-----*/
/*- File source          : GCC_FLASH.ld
*/
/*- Object               : Linker Script File for Flash Workspace
*/
/*- Compilation flag     : None
*/
/*-
*/
/*- 1.0 20/Oct/04 JPP    : Creation
*/
/*---------------------------------------------------------------------- 
-----*/

/*
  modified for the WinARM example - M.Thomas (not Atmel)
  - ramfunc-section/C++-support and more
*/

/*
//*** <<< Use Configuration Wizard in Context Menu >>> ***
*/


/*
// <h> Memory Configuration
//   <h> Code (Read Only)
//     <o>  Start <0x0-0xFFFFFFFF>
//     <o1> Size  <0x0-0xFFFFFFFF>
//   </h>
//   <h> Data (Read/Write)
//     <o2> Start <0x0-0xFFFFFFFF>
//     <o3> Size  <0x0-0xFFFFFFFF>
//   </h>
//   <h> Top of Stack (Read/Write)
//     <o4> STACK <0x0-0xFFFFFFFF>
//   </h>
// </h>
*/

/* Memory Definitions */

/* mt change code origin from 0x00000000 */
MEMORY
{
  CODE (rx) : ORIGIN = 0x00100000, LENGTH = 256K
  DATA (rw) : ORIGIN = 0x00200000, LENGTH = 64K
  STACK (rw) : ORIGIN = 0x00204000,LENGTH = 0x00000000
}

__FIRST_IN_RAM = ORIGIN(DATA);

/* Section Definitions */

SECTIONS
{
  /* first section is .text which is used for code */
  . = 0x0000000;

  .text :
  {
    KEEP(*(.vectorg))
    . = ALIGN(4);
    KEEP(*(.init))
    *(.text .text.*)                   /* remaining code */
    *(.gnu.linkonce.t.*)
    *(.glue_7)
    *(.glue_7t)
    *(.gcc_except_table)
    *(.rodata)                 /* read-only data (constants) */
    *(.rodata.*)
    *(.gnu.linkonce.r.*)
    . = ALIGN(4);
  } >CODE

  . = ALIGN(4);

  /* .ctors .dtors are used for c++ constructors/destructors */

  .ctors :
  {
    PROVIDE(_ctors_start_ = .);
    KEEP(*(SORT(.ctors.*)))
    KEEP(*(.ctors))
    PROVIDE(_ctors_end_ = .);
  } >CODE

  .dtors :
  {
    PROVIDE(_dtors_start_ = .);
    KEEP(*(SORT(.dtors.*)))
    KEEP(*(.dtors))
    PROVIDE(_dtors_end_ = .);
  } >CODE

  . = ALIGN(4);

  _etext = . ;
  PROVIDE (etext = .);

  /* .data section which is used for initialized data */
  .data : AT (_etext)
  {
  _data = . ;
  KEEP(*(.vectmapped))
  . = ALIGN(4);
  *(.fastrun .fastrun.*)
  . = ALIGN(4);
  SORT(CONSTRUCTORS)
  . = ALIGN(4);
  *(.data)
  *(.data.*)
  *(.gnu.linkonce.d.*)
  . = ALIGN(4);
  } >DATA

  . = ALIGN(4);

  _edata = . ;
  PROVIDE (edata = .);

  /* .bss section which is used for uninitialized data */
  .bss :
  {
  __bss_start = . ;
  _bss_start_ = . ;
  *(.bss)
  *(.bss.*)
  *(.gnu.linkonce.b.*)
  *(COMMON)
  . = ALIGN(4);
  } >DATA
  . = ALIGN(4);
  _bss_end_ = . ;

  _end = .;
  PROVIDE (end = .);

  .int_data :
  {
    *(.internal_ram_top)
  } > STACK



  /* Stabs debugging sections.  */
  .stab          0 : { *(.stab) }
  .stabstr       0 : { *(.stabstr) }
  .stab.excl     0 : { *(.stab.excl) }
  .stab.exclstr  0 : { *(.stab.exclstr) }
  .stab.index    0 : { *(.stab.index) }
  .stab.indexstr 0 : { *(.stab.indexstr) }
  .comment       0 : { *(.comment) }
  /* DWARF debug sections.
   Symbols in the DWARF debugging sections are relative to the beginning
   of the section so we begin them at 0.  */
  /* DWARF 1 */
  .debug          0 : { *(.debug) }
  .line           0 : { *(.line) }
  /* GNU DWARF 1 extensions */
  .debug_srcinfo  0 : { *(.debug_srcinfo) }
  .debug_sfnames  0 : { *(.debug_sfnames) }
  /* DWARF 1.1 and DWARF 2 */
  .debug_aranges  0 : { *(.debug_aranges) }
  .debug_pubnames 0 : { *(.debug_pubnames) }
  /* DWARF 2 */
  .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
  .debug_abbrev   0 : { *(.debug_abbrev) }
  .debug_line     0 : { *(.debug_line) }
  .debug_frame    0 : { *(.debug_frame) }
  .debug_str      0 : { *(.debug_str) }
  .debug_loc      0 : { *(.debug_loc) }
  .debug_macinfo  0 : { *(.debug_macinfo) }
  /* SGI/MIPS DWARF 2 extensions */
  .debug_weaknames 0 : { *(.debug_weaknames) }
  .debug_funcnames 0 : { *(.debug_funcnames) }
  .debug_typenames 0 : { *(.debug_typenames) }
  .debug_varnames  0 : { *(.debug_varnames) }

}


Regards
Flying