How to get current heap pointer?

Hi David_Cai,

maybe heap_end is declared in the linker script?

If you want to use symbols declared by the assembler or linker you can add an 'extern' declaration to your c code: e.g.

extern int heap_end;

Hope that helps,

Wolfgang

I have tried it, but it doesn't work...

Thanks anyway...

I'm confusing, I can see it in the global variables list, why I can't use it...

Anyone help...

David

Hi David_Cai,

I've looked some more at this problem.

The symbol 'heap_end' is defined in nios2_60\bin\nios2-gnutools\src\newlib\libgloss\nios2\nosys_sbrk.

It's definition is 'static char *heap_end;'

A static symbol is only visible (for the toolchain) in the current file. If you generate an objdump listing of your executable you can see that heap_end is listed as a local symbol.

So, if you try to reference this symbol in another file, it&#39;s the same as it wasn&#39;t defined at all. => >>undefined reference to `heap_end&#39;<<

Hope this helps,

Wolfgang

I&#39;m very appreciated for your kindly reply...

Could you kindly tell me how can you find the answer?

I hope to learn fishing skill and not only fishes.http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/happy.gif

Thanks again...

David

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originally posted by david_cai@Aug 11 2006, 07:01 AM

could you kindly tell me how can you find the answer?

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Hmm, let&#39;s see ...

1. I created a sample project to see if I would get the same problem.

2. I looked in the objdump file if the symbol was indeed defined (it was)

(If you want to know anything about an elf (file format used by gcc) executable/object file look at it with objdump)

3. I googled &#39;heap_end&#39;. a promising hit &#39;told&#39; me that heap_end was defined by the c-library.

4. I searched the c-lib sources in my local filesystem for &#39;heap_end&#39;

(I didn&#39;t use the explorer for that. I did use a program that searches the content of all files for &#39;heap_end&#39;).

5. Voilá, file found => static definition.

6. I know that static symbols are visible only in the current file.

You know, experience is difficult to explain...

Wolfgang

Thanks very very very much......

Your answer is very helpful for me.

In fact, I have done something like you, the only difference is that when I search on web , I can&#39;t get the info that heap_end is defined in c library.http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/happy.gif

Thanks again for your kindly reply,

David