How to get current heap pointer?

[Altera_Forum]

My project need to read current heap pointer, but I don't know how to implement it. 

In NiosII IDE, Variables Window, you can add a global variables for watching, and I find heap_end which is the one I looking for. but when I try to use it in my C code, the compiler report that heap_end undeclared.  Anyone help? David

[Altera_Forum]

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

[Altera_Forum]

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

[Altera_Forum]

Hi David_Cai, 

 I&#39;ve looked some more at this problem.  The symbol &#39;heap_end&#39; is defined in nios2_60\bin\nios2-gnutools\src\newlib\libgloss\nios2\nosys_sbrk. It&#39;s definition is &#39;static char *heap_end;&#39;  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

[Altera_Forum]

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

[Altera_Forum]

--- Quote Start ---  originally posted by david_cai@Aug 11 2006, 07:01 AM could you kindly tell me how can you find the answer? <div align='right'><{post_snapback}> (index.php?act=findpost&pid=17538)  --- quote end ---    --- Quote End ---   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

[Altera_Forum]

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