Difference Between Segmentation Fault And Bus Error
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Difference Between Segmentation Fault And Core Dump
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vote 25 down vote favorite 8 Difference between a bus error and a segmentation fault? Can it happen that a program gives a seg fault and stops for the first time and for the second time it may give a bus error and exit ? c share|improve this question edited May 2 '12 at 12:04 casperOne 58k10126202 asked May 8 '09 at 6:56 Thunderboltz 6253915 add a how to debug bus error comment| 6 Answers 6 active oldest votes up vote 34 down vote accepted On most architectures I've used, the distinction is that: a SEGV is caused when you access memory you're not meant to (e.g., outside of your address space). a SIGBUS is caused due to alignment issues with the CPU (e.g., trying to read a long from an address which isn't a multiple of 4). share|improve this answer answered May 8 '09 at 7:06 paxdiablo 489k1179701418 10 Memory mapped files can also generate SIGBUS. –bk1e May 8 '09 at 16:06 on arm SIGBUS can occur if you read a float from an address that is not 4 byte aligned –shoosh Mar 30 at 7:29 shoosh, I'm pretty certain that's covered by my second bullet point. –paxdiablo Mar 30 at 13:28 add a comment| up vote 11 down vote SIGBUS will also be raised if you mmap() a file and attempt to access part of the mapped buffer that extends past the end of the file, as well as for error conditions such as out of space. If you register a signal handler using sigaction() and you set SA_SIGINFO, it may b
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 ubuntu a process is trying to access memory that the CPU cannot physically how to fix bus error in linux address: an invalid address for the address bus, hence the name. In modern use on most architectures these are bus error python 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 http://stackoverflow.com/questions/838540/bus-error-vs-segmentation-fault 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 https://en.wikipedia.org/wiki/Bus_error 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 spe
- according to siginfo.h(3head) By Peteh-Oracle on Dec 08, 2006 Having asked https://blogs.oracle.com/peteh/entry/sigbus_versus_sigsegv_according_to a number of colleagues I failed to find a consistent answer to the question of the differences between SIGBUS and SIGSEGV. According to the Solaris signal(3head) man page we have: Name Value Default Event ... SIGBUS 10 Core Bus Error SIGSEGV 11 Core Segmentation Fault So I bus error dug a bit further and found that siginfo_t can tell you more about the origins of the signal, in particular we have, from the siginfo.h(3head) man page: Signal Code Reason _________________________________________________________________________ ... _________________________________________________________________________ SIGSEGV SEGV_MAPERR address not mapped to object SEGV_ACCERR invalid permissions for mapped object _________________________________________________________________________ SIGBUS difference between segmentation BUS_ADRALN invalid address alignment BUS_ADRERR non-existent physical address BUS_OBJERR object specific hardware error _________________________________________________________________________ Obviously this may be open to interpretation but that clarifies a few things for me. For the techie take a look at the OpenSolaris source code for the trap() function. Here we see the handling for various types of trap including page faults. For example, there's a section where a decision is made as to return SIGBUS or SIGSEGV: case T_WIN_OVERFLOW + T_USER: /\* window overflow in ??? \*/ case T_WIN_UNDERFLOW + T_USER: /\* window underflow in ??? \*/ case T_SYS_RTT_PAGE + T_USER: /\* window underflow in user_rtt \*/ case T_INSTR_MMU_MISS + T_USER: /\* user instruction mmu miss \*/ case T_DATA_MMU_MISS + T_USER: /\* user data mmu miss \*/ case T_DATA_PROT + T_USER: /\* user data protection fault \*/ switch (type) { ... /\* \* In