Segmentation Fault (Core Dumped) Là Gì

     
khi mình thực hành thực tế code với các bài liên quan đến con trỏ, như cây, liên kết list, hay bị lỗi Lỗi segmentation fault , vậy cho bạn hỏi lỗi này xuất hiện khi nào ? cùng hướng tra cứu cách giải quyết đơn giản++Sự học tập Không lúc nào Là Muộn++ ---Sướng Thì Ta Làm, thích hợp Thì đang Được---......Đôi khi quăng quật học cũng là 1 trong bước đột phá...

Bạn đã xem: Segmentation fault (core dumped) là gì

Bạn sẽ xem: Segmentation fault (core dumped) là gì

Bạn đã xem: Segmentation fault chip core dumped là gì




Bạn đang xem: Segmentation fault (core dumped) là gì

*

*

*



Xem thêm: Marketing Intelligence Là Gì ? Định Nghĩa, Ví Dụ, Giải Thích

*

*



Xem thêm: Random.Org Là Gì - Top 5 Công Cụ Quay Số Ngẫu Nhiên, Random Chữ

A segmentation fault occurs when a program attempts to lớn access a memory location that it is not allowed to access, or attempts khổng lồ access a memory location in a way that is not allowed (for example, attempting to write to lớn a read-only location, or lớn overwrite part of the operating system).Segmentation is one approach khổng lồ memory management & protection in the operating system. It has been superseded by paging for most purposes, but much of the terminology of segmentation is still used, "segmentation fault" being an example. Some operating systems still have segmentation at some logical level although paging is used as the main memory management policy.On Unix-like operating systems, a signal called SIGSEGV is sent to a process that accesses an invalid memory address. On Microsoft Windows, a process that accesses invalid memory receives the STATUS_ACCESS_VIOLATION exception. Common causesA few causes of a segmentation fault can be summarized as follows: * attempting to lớn execute a program that does not compile correctly. Cảnh báo that most compilers will not output đầu ra a binary given a compile-time error. * a buffer overflow. * using uninitialized pointers. * dereferencing NULL pointers. * attempting to access memory the program does not own. * attempting to lớn alter memory the program does not own (storage violation).Generally, segmentation faults occur because: a pointer is either NULL, points lớn random memory (probably never initialized to anything), or points khổng lồ memory that has been freed/deallocated/"deleted".e.g. Char *p1 = NULL; // Initialized khổng lồ null, which is OK, // (but cannot be dereferenced on many systems). Char *p2; // Not initialized at all. Char *p3 = new char; // Great! it"s allocated, delete p3; // but now it isn"t anymore.Now, dereferencing any of these variables could cause a segmentation fault. Examples Bus error exampleThis is an example of un-aligned memory access, written in the C programming language.#include int main(int argc, char **argv) int *iptr; char *cptr; #if defined(__GNUC__)# if defined(__i386__) /* Enable Alignment Checking on x86 */ __asm__("pushf orl $0x40000,(%esp) popf");# elif defined(__x86_64__) /* Enable Alignment Checking on x86_64 */ __asm__("pushf orl $0x40000,(%rsp) popf");# endif#endif /* malloc() always provides aligned memory */ cptr = malloc(sizeof(int) + 1); /* Increment the pointer by one, making it misaligned */ iptr = (int *) ++cptr; /* Dereference it as an int pointer, causing an unaligned access */ *iptr = 42; return 0;Compiling và running the example on Linux on x86 demonstrates the error:$ gcc -ansi sigbus.c -o sigbus$ ./sigbus Bus error$ gdb ./sigbus(gdb) rProgram received signal SIGBUS, Bus error.0x080483ba in main ()(gdb) x/i $pc0x80483ba : mov DWORD PTR ,0x2a(gdb) p/x $eax$1 = 0x804a009(gdb) p/t $eax & (sizeof(int) - 1)$2 = 1The GDB debugger shows that the immediate value 0x2a is being stored at the location stored in the EAX register, using X86 assembly language. This is an example of register indirect addressing.Printing the low order bits of the address shows that it is not aligned khổng lồ a word boundary ("dword" using x86 terminology). Segmentation fault exampleHere is an example of ANSI C code that should create a segmentation fault on platforms with memory protection: int main(void) char *s = "hello world"; *s = "H"; When the program containing this code is compiled, the string "hello world" is placed in the section of the program binary marked as read-only; when loaded, the operating system places it with other strings và constant data in a read-only segment of memory. When executed, a variable, s, is set lớn point khổng lồ the string"s location, và an attempt is made khổng lồ write an H character through the variable into the memory, causing a segmentation fault. Compiling such a program with a compiler that does not kiểm tra for the assignment of read-only locations at compile time, & running it on a Unix-like operating system produces the following runtime error:$ gcc segfault.c -g -o segfault$ ./segfaultSegmentation faultBacktrace from gdb:Program received signal SIGSEGV, Segmentation fault.0x1c0005c2 in main () at segfault.c:66 *s = "H";The conditions under which segmentation violations occur & how they manifest themselves are specific to lớn an operating system.Because a very common program error is a null pointer dereference (a read or write through a null pointer, used in C khổng lồ mean "pointer to no object" & as an error indicator), most operating systems maps the null pointer"s address such that accessing it causes a segmentation fault. Int *ptr = NULL; *ptr = 1;This sample code creates a null pointer, & tries to lớn assign a value khổng lồ its non-existent target. Doing so causes a segmentation fault at runtime on many operating systems.Another example is recursion without a base case: int main(void) main(); which causes the stack to overflow which results in a segmentation fault.