Bus Error

Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers Bus Error
# 1  
Old 11-09-2001
Bus Error

This may belong in the C Programming forum, but here goes anyway...

What would cause a bus error? I searched google for a cause, but came up with some conflicting reports...
Could it be caused by [lack of] disk space?
A lot of the pages I found mentioned linking with the incorrect versions of the library. But in that case, would it compile correctly?

Basically, I am curious as to why we had a job dump core on a bus error. It ran nearly to normal completion time, then simply poo-pood.

In the case that it may make a difference, it's a job that interfaces with an Oracle database on HP-UX 11. The things that had changed were that the process was recompiled, AND we were at 96% (df -k) on that disk...

Not too important for me to know right now, but I am curious, and who wants to wait for developers to tell me what happened? Smilie
# 2  
Old 11-09-2001
The bus in question is the address buss and it contains an illegal value. This is almost always the result of dereferencing a pointer that contains an illegal value.

Here is a program that, I think, will compile with every C or C++ compiler, but should cause a bus error when the second printf is attempted...

#ifdef __STDC__
#ifdef __cplusplus

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

int main(int argc, char *argv[])
char *argv[];
      double d = 1.23456789;
      double *p = &d;
      printf ( " d = %f \n" , *p);
      p = (double *)((char *)p + 1);
      printf ( " d = %f \n" , *p);

Last edited by Perderabo; 01-16-2005 at 04:30 PM.. Reason: Remove html which is no longer supported
# 3  
Old 11-10-2001
I only know that if one trys to access a memory which in a readonly segment, the system will bumpup a Bus Error signal.
# 4  
Old 11-10-2001
Do you have the source for the program? You could always examine the core to find out what is happening.
# 5  
Old 11-10-2001
Originally posted by tonyt
I only know that if one trys to access a memory which in a readonly segment, the system will bumpup a Bus Error signal.
By "access" I guess you mean trying to store something there. Not to belabor the obvious, but it is legal to read a read-only segment.

There are two signals that can be delivered to a process that attempts something with an illegal memory address:

SIGBUS (ksh will say Bus error(coredump))
SIGSEGV (ksh will say Memory fault(coredump))

I've been looking through my library and I can't find any documentation that states which signal must be delivered under a specific condition. It may be that some versions of unix only use one or the other for everything. The kernel really depends on the cpu to catch these and it may be that some cpu's simply have a single trap to handle all bad addresses.

Still to me these errors have slightly different meanings, although I must admit that this is based mostly on C programming in an HP-UX environment.

SIGBUS means that you have asked to cpu to do something that is impossible. More to the point, the cpu can catch this error immediately by looking at the virtual address. There is no need to even attempt to convert the virtual address to a physical address. This is why cpu's bother to have a two-tiered check on an address. Converting a virtual address to a physical address can be a somewhat expensive operation.

SIGSEGV means that you have asked the cpu to do something that is illegal. If the kernel wanted to, it could fiddle with things to render the attempted operation legal. This error is caught after the attempted conversion of the virtual address to a physical address.

I would tend to expect that the situation tonyt is describing would result in a SIGSEGV rather than a SIGBUS....except that if you have a pointer that is both misaligned and in the wrong segment, you won't get both signals, you only get a SIGBUS. If an int is 4 bytes on your system and you try to store an int at random addresses in a read-only segment, then yes 75% of the time you will get a SIGBUS, while 25% of the time your pointer is aligned and you get the SIGSEGV.

Still tonyt may have a system that works differently than mine. And if a system can only deliver a single signal for address problems, SIGBUS would be my choice.
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Programming

Bus Error: 10...Help please!

Hi all, I am writing a phonebook program to store names and number using a list. Here is the code for the function which allows the user to enter the name and number (where the error occurs). //THIS FUNCTION ADDS A NEW ENTRY TO THE phonebook_list void insert(void){ //variables int... (5 Replies)
Discussion started by: kdejan
5 Replies

2. Programming

Bus error in tree insertion

Hi, I am new to C++ and unix. I am trying to write a programm for inserting elements into a binary tree. To get the code flow I used few Couts and m facing buss error while insertion. Below is the code snippet. explainations needed. thanks :) #include <iostream.h> struct mytree { int... (1 Reply)
Discussion started by: vineetjoshi
1 Replies

3. Programming

Bus error

Hi everyone, I have a GUI project and when I run it and left in idle state for a long time(there is nothing done, just opened GUI, no more actions),I get bus error after trying to do anything with it. I've tried to build it in debug mode and use gdb, but I don't get any error in debug mode.It... (3 Replies)
Discussion started by: sisi
3 Replies

4. HP-UX

Bus Error

I am getting bus error when i include "#!/bin/ksh". If i remove interpreter then script is working. Can anyone explain this and how can i avoid this error? Operating System is HP-UX B.11.23 U 9000/800 1091834454 (2 Replies)
Discussion started by: anbu23
2 Replies

5. HP-UX

Need help on Bus error(coredump)

Hi all, I am quite weak in C but I need to get some work done. Hope someone can help me out. I keep getting this error when i try to run my C application in my HP-UX 10.20 machine. Some code snippet: Month(DBTime) =====This is a function which will return variable "CutOffTime" to be use... (5 Replies)
Discussion started by: Vision©
5 Replies

6. UNIX for Dummies Questions & Answers

bus error (coredump)

Hi all, I am getting bus error problem in SunOS. Can you please help me out in this regard. Actually, my entire code till the last line has been executed. But after tht i am getting a bus error. Please help me. Thanks in advance. Charu. (4 Replies)
Discussion started by: charu
4 Replies

7. Programming

BUS error

Hi! I've got a program which runs fine under Linux, but I have compiled it to run under SunOS 5.8 in a Sparc computer, and now it sometimes fails with "bus error". Ussing gdb I surfed to the error line, which is *pointer = some_vector; where some_vector is a 16 byte struct (4 integers)... (1 Reply)
Discussion started by: shesatmine
1 Replies

8. UNIX for Advanced & Expert Users

Bus Error(coredump)

Hi, I am using HP-UX. While i try to run the Sqlplus command using the shel script in encounter the following error: <shell script name>: some number Bus Error(coredump) What may be the reason behind this. I read few previous threads in this forum where i found some similar case. There it was... (2 Replies)
Discussion started by: Jayesh
2 Replies

9. UNIX for Dummies Questions & Answers

Bus error(coredump

aix 5.3 ML1 system was functioing well, when suddenly telnet session hung and then I got the following message "Bus error(coredump)" would appreciate if anyone would assist as to what to do next. (3 Replies)
Discussion started by: Student37
3 Replies

10. UNIX for Dummies Questions & Answers

bus error on solaris

Hi there I am running soalris 9 on a sun fire 480r and all of a sudden (today) whenever the users run the command `top` we get the following message `bus error` does anybody have any information on what this is all about and whether there is a routine i can perform to gather more... (3 Replies)
Discussion started by: hcclnoodles
3 Replies
Login or Register to Ask a Question