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Forum: ARM programming with GCC/GNU tools linker error undefined ref to `_sbrk'


Author: Ameya Hardikar (Company: Shalaka Tech. Pvt. Ltd.) (ameya)
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Hello All,

I am using LM3S811 evaluation kit and code red development tools for 
firmware development.

Whenever i call functions atoi or atof from stdlib, linker gives 
following error.

: In function `_sbrk_r':
sbrkr.c:(.text+0x12): undefined reference to `_sbrk'
collect2: ld returned 1 exit status
make: *** [SHT11_Rev5oct.axf] Error 1

For this problem,I have referred link  http://embdev.net/topic/129753 on 
this forum.

As per the instructions i have edited linker script in 'standalone.o'
. Also created syscalls.c and added to my project. But its unable to 
link; giving error 'undefined reference to `_sbrk''

My project folder is attached for ref.

What could be reason? Kindly help me.
Thanks in advance :-)

Ameya

Author: Jörg Wunsch (dl8dtl) (Moderator)
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Ameya Hardikar wrote:

> As per the instructions i have edited linker script in 'standalone.o'
> . Also created syscalls.c and added to my project. But its unable to
> link; giving error 'undefined reference to `_sbrk''

Because there is no function named _sbrk in it.  You call it sbrk.

Author: Gilles Bulthé (Guest)
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Ameya Hardikar,
did you find the solution ?

I 've got similar probleme with my compilation :


// output of "make" :
  LD    gcc/uart_check.axf
/opt/CodeSourcery/arm-2009q1/bin/../lib/gcc/arm-none-eabi/4.3.3/../../.. 
/../arm-none-eabi/lib/thumb2/libc.a(lib_a-sbrkr.o):  In function 
`_sbrk_r':
sbrkr.c:(.text+0x12): undefined reference to `_sbrk'
make: *** [gcc/uart_check.axf] Error 1
/* end of quotation */

It looks similar, true ? Any suggestion ?

Jörg Wunsch, the "_sbrk" is in a library, and it is not normal that this 
error occur, I do not understand...

Gilles Bulthé

Author: Gilles Bulthé (Guest)
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In fact,
I have this code :
==========quotation :
typedef struct historyList{
    char* CmdLine;
    int CmdSize;
    struct historyList* prev;
    struct historyList* next;
} history;


history*
UARTHistoNew()
{
    history* New=(history*)malloc( sizeof(history));
    New->CmdLine = "";
    New->CmdSize = 0;
    New->prev=NULL;
    New->next=NULL;

    return New;
}

[...]
[in my main function :]
    static history *pHistoList=NULL;
    // init the histo (Normalement, ONLY ONE TIME !) :
    if (pHistoList==NULL) pHistoList = UARTHistoNew();
=========end of quote

And the compilation pb disappears when I disable the last line ("if 
(pHistoList==NULL) pHistoList = UARTHistoNew()").

Can anyone help me ?
Thanks in advance.

Gilles.

Author: Tilo (Guest)
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Hi

Do you want to use dynamic memory or something like that? The "newlib" 
provides basic functions which are part of the standard C library. You 
have to provide hardware close functions yourself.

You can take a look at http://sourceware.org/newlib/ a search for 
"system calls"

Cheers, Tilo

Author: Gilles Bulthé (Guest)
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Tilo,
thank you so much.

I learn by your link and 
http://tech.dir.groups.yahoo.com/group/lpc2000/mes... that 
malloc needs dynamics library witch needs _sbrk_r, etc.

So, I will use another way, with no malloc.
Ex :
===quote :
history*
UARTHistoNew()
{
//    history* New = (history*)malloc( sizeof(history));
    history New;
    New.CmdLine = "";
    New.CmdSize = 0;
    New.prev=NULL;
    New.next=NULL;

    return &New;
}
[etc]
===========end

Correct ? I think this way will allow me to avoid using malloc and 
dynamic livraries...
Thanks,
Gilles.

Author: Ameya Hardikar (Company: Shalaka Tech. Pvt. Ltd.) (ameya)
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Hello Gilles,

Yeah i got the problem solved. But at a cost of loosing much of my code 
memory space. You can change c library which your project is referring. 
Currently you may be using newlib(none). Change this to newlib(nohost) 
and  build your code. But then newly generated .axf will be of almost 
double size than previous one. Solution is to define_sbrk in your 
project and build it.

Keil IDE provides syscall.c file with the definition of _sbrk. refer it.

also check this:
http://support.code-red-tech.com/CodeRedWiki/CLibrary

Thank you,
Ameya

Author: Stefan Ernst (sternst)
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Gilles Bulthé wrote:

> Correct ? I think this way will allow me to avoid using malloc and
> dynamic livraries...

No. After the function returned, "New" does no longer exist.
If the function is really called only once, you can make "New" static 
and it will work then.

Author: Jörg Wunsch (dl8dtl) (Moderator)
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Gilles Bulthé wrote:

> Jörg Wunsch, the "_sbrk" is in a library, ...

No, it was supposed to be in one of Ameya's source files, but he
misnamed it sbrk (rather than _sbrk), so the linker did not find
it.

Author: Gilles Bulthé (Guest)
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Thank you to all of you.

The way to change the dynamic library in order to have it for my 
embedded application may be too hard. So I'll give up here, after 
regarding this "high-level" solution.

Ameya, your solution may be THE one, but for my little application, I 
will prefer working in static than in dynamic. More stable. And I have 
small memory space.

Stefan, thank for your note ! For sure, I spoke to fast... 
(unforgivable!)

Best regards,
Gilles.

Author: Gilles Bulthé (Guest)
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That's true, Jörg, I learned it after, sorry. It was a linker problem.

Real Thanks to all of the reactive members of this dynamic (library ?) 
forum !
See you,
Gilles.

Author: Qduda 12345 (Company: student) (qduda)
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Sorry if this is not related to your topic, in another thread and saw 
this topic was related, i just "cross-read" this thread. ;-)
But maybe this might help you "http://embdev.net/topic/129607". I got 
the same issue and solved it in just implementing a stub function for 
_sbrk. I dont use dynamic memory allocation in my sourcecode, but the 
linker wants a regerence to _sbrk... if you dont use malloc (or equal 
functions) you should be safe with a stub.

Author: Gilles Bulthé (Guest)
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Qduda, thanks for your advice :-)

if I really have to use it in the future, it would help me.
Well done !
Gilles.

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