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Char array and .data section

Arifa Khan
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Note: This was originally posted on 11th January 2011 at http://forums.arm.com

Hi,

I've been trying to use string literals in my C code, however I'm having a really odd problem.

I've condensed my code to do just a basic store string literal in a char variable, and output element value:

Code 1:

#include "generic.h"
#include "stdlib.h"
#include "string.h"

int main(void) {

char chartest[4]="HEL";
uart_send_num(chartest[2]); //function I've written to output the numeric value of data, to my serial port

}

Result 1:
0076

So that result is what I expected to see (ASCII : L = 76).

If I change the array size to anything bigger than 4 elements:

Code 2:

#include  "generic.h"
#include "stdlib.h"
#include "string.h"

int main(void) {

char chartest[5]="HELL";
uart_send_num(chartest[2]);

}

Result 2:
0000

I can't understand why this would be happening.
I'm using Codesourcery gcc with Eclipse SDK, but still trying to figure out how everything works, so I haven't got all the libraries and maybe even linker script working correctly, i.e. printf, malloc, etc. doesn't work, therefore I wrote my own uart routine.

Part of my linker script is as follows:

.text : {
     CREATE_OBJECT_SYMBOLS
     *(.text .stub .text.* .gnu.linkonce.t.*)
     *(.plt)
     *(.gnu.warning)
     *(.glue_7t) *(.glue_7)      /* NOTE: placed already in .fastcode */

     . = ALIGN (4);
     /* These are for static constructors and destructors under ELF */
     KEEP (*crtbegin.o(.ctors))
     KEEP (*(EXCLUDE_FILE (*crtend.o) .ctors))
     KEEP (*(SORT(.ctors.*)))
     KEEP (*crtend.o(.ctors))
     KEEP (*crtbegin.o(.dtors))
     KEEP (*(EXCLUDE_FILE (*crtend.o) .dtors))
     KEEP (*(SORT(.dtors.*)))
     KEEP (*crtend.o(.dtors))

     *(.rodata .stub .rodata.* .gnu.linkonce.r.*)

     *(.ARM.extab* .gnu.linkonce.armextab.*)
     *(.gcc_except_table)
     *(.eh_frame_hdr)
     *(.eh_frame)

     *(.init)
     *(.fini)

     PROVIDE_HIDDEN (__preinit_array_start = .);
     KEEP (*(.preinit_array))
     PROVIDE_HIDDEN (__preinit_array_end = .);
     PROVIDE_HIDDEN (__init_array_start = .);
     KEEP (*(SORT(.init_array.*)))
     KEEP (*(.init_array))
     PROVIDE_HIDDEN (__init_array_end = .);
     PROVIDE_HIDDEN (__fini_array_start = .);
     KEEP (*(.fini_array))
     KEEP (*(SORT(.fini_array.*)))
     PROVIDE_HIDDEN (__fini_array_end = .);
} >ROM

/* .ARM.exidx is sorted, so has to go in its own output section.  */
.ARM.exidx : {
     __exidx_start = .;
     *(.ARM.exidx* .gnu.linkonce.armexidx.*)
     __exidx_end = .;
} >ROM
_etext = .;

.data : {
ram_sdata = .;
     __data_load = LOADADDR (.data);
     __data_start = .;
      KEEP(*(.jcr))
     *(.got.plt) *(.got)
     *(.shdata)
PROVIDE(_sdata = . );
     *(.data .stub  .data.* .gnu.linkonce.d.*)
. = ALIGN(4);

     . = ALIGN (4);
PROVIDE(_edata = . );
      _edata = .;
} >RAM AT>ROM

.bss : {
     __bss_start = . ;
     *(.shbss)
     *(.bss .stub .bss.* .gnu.linkonce.b.*)
     *(COMMON)
     . = ALIGN (4);
PROVIDE(_sbss = . );

             *(.bss)

             . = ALIGN(4);

             PROVIDE(_ebss = . );

     __bss_end = .;
} >RAM

PROVIDE(__heap_start__ = __bss_end );
__HEAPSIZE__ = 4097;

I'm presuming it's something to do with my linker script?

I've tried searching for a similar problem, but nothing relevant seems to come up. Would anyone have any suggestions or ideas on what may be the problem?
At this point, even any guesses would be more than welcome!

Thanks!
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