Strange string problem

[hunter]

Hello all,

i have big problems with strings in my user applications ... if i want to send the kernel strings from a user application there are strange problems ..

For example: If i use this way to write a string it works ...

Code: Select all

	string[0] = 'A';
	string[1] = 'B';
	string[2] = 'C';
	string[3] = '\0';

But if i use this way ... it doesn't work ...

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char test[4] = "ABC\0";
	
	for( i=0;i<4;i++ )
		string[i] = test[i];

Do the codes the same one ?? Or is it possible the second code doesn't do the same as the first one ??

... sorry for my bad english ...

Hunter

[Combuster]

Sounds like a missing .rodata in your linker script... have you checked that?

[hunter]

Sounds like a missing .rodata in your linker script... have you checked that?

What do mean with .rodata .. could you give me an example please ...

Hunter

[Combuster]

gcc normally puts strings in a special section in your executable: .rodata

If you use a linker script, you should check that it copies .rodata to the output. (common knowledge. see one of Solar's post for an example)

[hunter]

Hello,

I have add the .rodata part in my linker file ... but it doesn't work ...
I have two linker files one for the kernel and an other for the user programs ..

Here the Linkerfile for the Kernel:

Code: Select all

OUTPUT_FORMAT( "binary" )
INPUT( ....................... )
ENTRY(start)
SECTIONS
{
  .text 0x100000 : {
    *(.text)
    *(.rodata*)
    . = ALIGN(4096);
  }
  .data : {
    *(.data)
  }
  .bss :  {					
    *(.bss)
  }
}

And her is the linkerfile for the Userprograms:

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OUTPUT_FORMAT("binary")
ENTRY(_main)

Which linkerfile i have to edit that the kernel can see the strings from the userprograms ?

I hope somebody could help me ...

Hunter

[iammisc]

You need to use the same style of linker script for userspace apps too.

try this

Code: Select all

OUTPUT_FORMAT( "binary" )
INPUT( ....................... )
ENTRY(start)
SECTIONS
{
  . = wherever user space things are loaded
  .text : {
    *(.text)
    *(.rodata*)
    . = ALIGN(4096);
  }
  .data : {
    *(.data)
  }
  .bss :  {               
    *(.bss)
  }
}

[muisei]

Why do you add the terminating '0' to the string?The compiler should add it itself.

char test[4]='A,'B','C','\0' is equal to char test[4]="ABC"

[Otter]

You can also use a simple stdlib you link in before the rest of your kernel/program:

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$ ld stdlib.o kernel.o -o kernel

This stdlib could call the main function of the kernel.