Gdb Bus Error
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challenged and removed. (July 2015) (Learn how and when to remove this template message) In computing, a bus error is a fault raised by hardware, notifying an operating system (OS) that
Bus Error C++
a process is trying to access memory that the CPU cannot physically bus error linux address: an invalid address for the address bus, hence the name. In modern use on most architectures these are
How To Debug Bus Error
much rarer than segmentation faults, which occur primarily due to memory access violations: problems in the logical address or permissions. On POSIX-compliant platforms, bus errors usually result in the SIGBUS signal bus error (core dumped) linux being sent to the process that caused the error. SIGBUS can also be caused by any general device fault that the computer detects, though a bus error rarely means that the computer hardware is physically broken—it is normally caused by a bug in a program's source code.[citation needed] Bus errors may also be raised for certain other paging errors; see below. Contents 1 how to solve bus error in linux Causes 1.1 Non-existent address 1.2 Unaligned access 1.3 Paging errors 2 Example 3 References Causes[edit] There are at least three main causes of bus errors: Non-existent address[edit] Software instructs the CPU to read or write a specific physical memory address. Accordingly, the CPU sets this physical address on its address bus and requests all other hardware connected to the CPU to respond with the results, if they answer for this specific address. If no other hardware responds, the CPU raises an exception, stating that the requested physical address is unrecognized by the whole computer system. Note that this only covers physical memory addresses. Trying to access an undefined virtual memory address is generally considered to be a segmentation fault rather than a bus error, though if the MMU is separate, the processor can't tell the difference. Unaligned access[edit] Most CPUs are byte-addressable, where each unique memory address refers to an 8-bit byte. Most CPUs can access individual bytes from each memory address, but they generally cannot access larger units (16 bits, 32 bits, 64 bits and so on) without these units being "aligned" to a specif
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Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like https://en.wikipedia.org/wiki/Bus_error you, helping each other. Join them; it only takes a minute: Sign up gdb: set a breakpoint for a SIGBUS handler up vote 9 down vote favorite 4 I'm trying to debug a simple stop-and-copy garbage collector (written in C) using GDB. The GC works by handling SIGBUS. I've set a breakpoint at the top of my http://stackoverflow.com/questions/2044179/gdb-set-a-breakpoint-for-a-sigbus-handler SIGBUS signal handler. I've told GDB to pass SIGBUS to my program. However, it doesn't appear to work. The following program (explained inline) shows the essence of my problem: #include
Programming Boards C Programming help needed on debugging "bus error" Getting started with C or C++ | C Tutorial | C++ Tutorial | C and C++ FAQ | Get a compiler | Fixes http://cboard.cprogramming.com/c-programming/90001-help-needed-debugging-bus-error.html for common problems Thread: help needed on debugging "bus error" Thread Tools Show Printable Version Email this Page… Subscribe to this Thread… Display Linear Mode Switch to Hybrid Mode Switch to Threaded Mode 05-18-2007 #1 wuhua View http://kb.mit.edu/confluence/pages/viewpage.action?pageId=3907165 Profile View Forum Posts Registered User Join Date May 2007 Posts 2 help needed on debugging "bus error" Hello. This is my first post here. Thanks for your help. I have been coding a program which handles bus error many arrays of strings. The program sometimes (there is a random number generator in the codes) will crash with a message "bus error". I am guessing it's caused by those strings. I tried to find out where exactly the error occurs by adding print lines inbetween coding blocks like the following: 100 printf("100\n"); codes... 200 printf("200\n"); codes... 300 printf("300\n"); However, it didn't help because the output will be something like 100 200 300 100 20 gdb bus error which means it crashes in the middle of printing 200? Anyway, because i can't exactly pin down which part of the code causes the problem, it is very hard for me to fix it. Any ideas? Thanks a lot. 05-18-2007 #2 Salem View Profile View Forum Posts and the hat of int overfl Join Date Aug 2001 Location The edge of the known universe Posts 34,484 > there is a random number generator in the codes I would avoid calling srand() until you're sure everything works. At least then you'll get some measure of repeatability. As for the bus error, that is much harder. If you run it inside the debugger, it will trap the BE and stop the program where the problem is first identified. Unfortunately, this is seldom related to the root cause of the problem which is likely to be somewhere else in the code. First check that all your pointers are at least initialised to NULL, if you don't initialise them when you declare them. Also check all loops which subscript into arrays, to make sure they're in bounds as well. int arr[N]; would be indexed with for ( i = 0 ; i < N ; i++ ) Starting at 1, or doing <= N are common mistakes. If you're still stuck and the code isn'
view Printable view Export to Adobe Acrobat (PDF) Export to Microsoft Word Email this page Other pagesHome page Dashboard News Recent updates RSS feed builder Index Site map Labels Attachments index People Directory AccountLog in History History What does "Bus Error" or "Segmentation Fault" mean? These statements mean that there's a bug in the program. If you're able to consistently reproduce this bug in a piece of supported software, please submit a bug report using the "sendbug" command. If you're interested in learning more details and how to debug your own programs, read on. These errors often mean that the program was trying to access a memory location outside its address space. The computer detected this problem and sent a signal to your program, which caused it to abort. Things that cause bus errors and segmentation violations are typically out-of-bounds array references and/or references through uninitialized or mangled pointers. Look very closely in your program for bizarre things like that. A common example is: int c; scanf("%d", c); instead of the correct version: int c; scanf("%d", &c); There are a number of methods for finding out where the program went out of bounds. One method is to use printf() statements to determine how far the program is getting before it crashes, and to print out the contents of interesting variables. A more sophisticated method is using a debugger, such as "gdb". If you need to debug your program, you may want to enable a core dump. Usually, those two messages above would also have "(core dumped)" by them, indicating that the program wrote an image of its current memory into a file called "core" in that directory. Athena turned this off by default, since for most people "core" is just a waste of disk space. If you want to turn it back on again, type 'quota -v' and find out how many