Local Variable vs Global Variable

[华文]

hi ! I have run the simple Hello world program on the or1200 processor following the  Basic custom openrisc system HW/SW tutorial.
The hardware only contains the processor, debug unit,ram and the uart unit.
And  I find a  very strange  phenomenon I do not konw why.
That is  if I modify the hello.c code by making the  'char *str = "Hello world!!!\n" ' inside the main  funciton, the hello world program can not run on the or1200 processor.

By modification,there is not a .data section.  Thank you for your attention, looking forward the answer.

 

the original codes:

char *str = "Hello world!!!\n";
int main (void)
{
  char *s;

  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;
}

---->by modification:
int main (void)
{
  char *s;
  char *str = "Hello world!!!\n";
  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;

}

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[Robert Cragie]

There won't be a .data section as the pointer is now an auto variable and will be either a register or on the stack (most likely a register). So there is no static variable anymore. The string itself will I presume be stored in .rodata - check the output using or32-uclinux-objdump.

Robert Cragie, Design Engineer
_______________________________________________________________
Jennic Ltd, Furnival Street, Sheffield, S1 4QT,  UK
http://www.jennic.com  Tel: [phone]
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-----Original Message-----
From: openrisc-bounces@... [mailto:openrisc-bounces@...]On Behalf Of »ªÎÄ
Sent: 24 October 2007 09:17
To: openrisc@...
Subject: [openrisc] Local Variable vs Global Variable

hi ! I have run the simple Hello world program on the or1200 processor following the  Basic custom openrisc system HW/SW tutorial.
The hardware only contains the processor, debug unit,ram and the uart unit.
And  I find a  very strange  phenomenon I do not konw why.
That is  if I modify the hello.c code by making the  'char *str = "Hello world!!!\n" ' inside the main  funciton, the hello world program can not run on the or1200 processor.

By modification,there is not a .data section.  Thank you for your attention, looking forward the answer.

 

the original codes:

char *str = "Hello world!!!\n";
int main (void)
{
  char *s;

  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;
}

---->by modification:
int main (void)
{
  char *s;
  char *str = "Hello world!!!\n";
  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;

}

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http://www.opencores.org/mailman/listinfo/openrisc

[beking]

hi,华文:
now i want to run "hello world " on my dev_board(cycloneII),but when compiling all .v files,some errors coming,did you come into contact with this error in your experiment,.....

华文 wrote:

hi ! I have run the simple Hello world program on the or1200 processor
following the  Basic custom openrisc system HW/SW tutorial.
The hardware only contains the processor, debug unit,ram and the uart unit.
And  I find a  very strange  phenomenon I do not konw why.
That is  if I modify the hello.c code by making the  'char *str = "Hello
world!!!\n" ' inside the main  funciton, the hello world program can not run
on the or1200 processor.
By modification,there is not a .data section.  Thank you for your attention,
looking forward the answer.

the original codes:
*char *str = "Hello world!!!\n";*
int main (void)
{
  char *s;

  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;
}

---->by modification:
int main (void)
{
  char *s;
  *char *str = "Hello world!!!\n";*
  uart_init ();
  for (s = str; *s; s++)
    uart_putc (*s);

  while (1)
    uart_putc (uart_getc () + 1);

  return 0;

}

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[Enrico Weigelt, metux IT service]

* Robert Cragie <rcc@...> wrote:

> There won't be a .data section as the pointer is now an auto variable and
> will be either a register or on the stack (most likely a register). So there
> is no static variable anymore. The string itself will I presume be stored in
> .rodata - check the output using or32-uclinux-objdump.

BTW: what happens if that global variable is changed to static const char* ?


cu
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