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Today while testing some program I’d encountered this problem. So i’ve digged bit more into it.

The reasons for bus error are

1)accessing unaligned memory addresses: if we are accessing a memory address which is unaligned, this can potentially raise SIGBUS signal on some systems on others this may just slowdown the reading process.

2)accessing a address out of range or non existant address: if the address we are giving is not exist in our enire hardware address range then data bus going to return with error, this will trigger SIGBUS.

3)accessing undefined address: if we try to access undefined address, this may result in segmentation fault

Here is an example which explains the above stuff….

#include <stdio.h>
#include <signal.h>
#include<stdlib.h>

void catchsig(int sig)
{
  if (sig==SIGSEGV)
  {
    printf("segmentation fault\n");
  }
  else if (sig==SIGBUS)
  {
    printf("bus error\n");
  }
}

int main(int argc, char **argv)
{

  char data[sizeof(unsigned long)];
  int *x; int y;

  signal(SIGSEGV, catchsig);
  signal(SIGBUS, catchsig);

  x = (int *)(data + 1);
  y = *x; /*causes bus error on some platforms*/

  x = (int *)0xffffffff /*lets say this address is not in our hardware*/
  y = *x; /*results bus error, as address bus returns with an error*/

  x = (int *)0×100; /*undefined address*/
  y = *x;  /*casues segmentation fault on some machines*/

  return 0;
} 

[tags]bus error, SIGBUS, sigmentation fault, sigbus error, sigbus signal, bus errors[/tags]

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• Bus Error
• String Pattern Matching: Write a function that checks for a given pattern at the end of a given string
• Does delete delete the pointer, or the pointed-to-data?
• C++ Basics Tutorial - Lesson 10
• Can we use printf() in an ISR?

This entry was written by openasthra and posted on January 3, 2007 at 1:41 pm and filed under Embedded Systems Programming. Bookmark the permalink. Follow any comments here with the RSS feed for this post. Post a comment or leave a trackback: Trackback URL.