Heap Allocation - Integrating MQX and PEG+

[OldNick]

Have ported the BSP to my platform (K20) and worked through many of the MQX examples, which all work fine.

Now trying to integrate PEG+ into the platform, I have got to the point of building my first GUI application.

But at the conclusion of the make I get a linker error telling me there is no heap allocated.

Warning[Lp012]: no sections with name HEAP included - special symbol HEAP$$Base (referenced from xgetmemchunk.o(dl7M_tln.a)) will  be zero.

When I run the code, it drops into MQX-idle at the first point where the new operator is called.

I am using the icf provided with the MQX examples, which (as supplied) has neither stack nor heap.  This confused me a bit, since C-stack is usually the first thing set up by the RTL.  Therefore I assume that MQX handles stack and heap on its own.?

Anyway, I modified the icf from within IAR IDE to give myself a 64k heap, but still got the same linker error.  modified icf attached

What I really want to do is put all the GUI volatile stuff into an offchip SRAM which I have put on the board, leaving the On-chip memory for application stuff.  But for now, anything that gives me a heap section would be helpful.

Can you suggest anything?  Which manuals should I read?

[KJFPE]

HI 

I had the same problem, try something like this changing the value 0x0800 dependent upon your needs

define block HEAP with size = 0x0800, alignment = 8{ };

place in RAM_region {block HEAP};

[OldNick · Accepted solution]

OK...sorted now, got help from compiler tech support.

Did not need to define a heap...DID need to override the new operator so that it uses mqx "_mem_alloc"

(Have also been advised to watch out for exception handling, but that depends on level of C++ selected.)

[KJFPE]

can I ask how you overode the new operator to use mqx "_mem_alloc" 

thanks

[OldNick]

---

KJFPE wrote:

can I ask how you overode the new operator to use mqx "_mem_alloc" 

thanks

---

Somewhere in your cpp code, you need something like these two

void* operator new (unsigned int size)
{
    void *p = _mem_alloc_system(size);

    if (!p)
    {
//catch null response
    }   
    return(p);
}   

void operator delete(void *p)
{
   uint_32 result = _mem_free(p);
   if (result != MQX_OK)
   {
      _task_set_error(result);
   }
}  

And of course, you may need the array versions as well.

The functions are provided as part of the graphics library, so I have had to mangle them slightly for this post.  I hope that gves you enough to get the general idea.  If you are using PEG+ there is a define in mqxpeg.hpp (PEG_NEW_DELETE) which is commented out, and shouldn't be.  I think I have said all I ought to.