Lúc bản thân thực hành thực tế code cùng với các bài bác tương quan đến bé trỏ, nlỗi cây, link danh mục, thường bị lỗi Lỗi segmentation fault , vậy cho doanh nghiệp hỏi lỗi này lộ diện bao giờ ? và phía tra cứu phương pháp xử lý 1-1 giản++Sự Học Không Bao Giờ Là Muộn++ ---Sướng Thì Ta Làm, Thích Thì Sẽ Được---......Thông thường bỏ học tập cũng là một trong bước cải tiến vượt bậc...
A segmentation fault occurs when a program attempts to access a memory location that it is not allowed khổng lồ access, or attempts khổng lồ access a memory location in a way that is not allowed (for example, attempting lớn write to a read-only location, or khổng lồ 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 It has been superseded by paging for most purposes, but much of the terminology of segmentation is still used, "segmentation fault" being an example.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 màn chơi 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. Comtháng causesA few causes of a segmentation fault can be summarized as follows: * attempting lớn exedễ thương a program that does not compile correctly. cảnh báo that most compilers will not output a binary given a compile-time error. * a buffer overflow. * using uninitialized pointers. * dereferencing NULL pointers. * attempting lớn access memory the program does not own. * attempting to alter memory the program does not own (storage violation).Generally, segmentation faults occur because: a pointer is either NULL, points to random memory (probably never initialized lớn anything), or points to lớn memory that has been freed/deallocated/"deleted".e.g. char *p1 = NULL; // Initialized lớn 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 $0x40000,(%rsp) popf");# endif#endif /* malloc() always provides aligned memory */ cptr = malloc(sizeof(int) + 1); /* Increment the pointer by one, making it misaligned */ iptr = (int *) ++cptr; /* Dereference it as an int pointer, causing an unaligned access */ *iptr = 42; return 0;Compiling & running the example on Linux on x86 demonstrates the error:$ gcc -ansay mê sigbus.c -o sigbus$ ./sigbus Bus error$ gdb ./sigbus(gdb) rProgram received signal SIGBUS, Bus error.0x080483tía in main ()(gdb) x/i $pc0x80483ba : mov DWORD PTR ,0x2a(gdb) p/x $eax$1 = 0x804a009(gdb) p/t $eax và (sizeof(int) - 1)$2 = 1The GDB debugger shows that the immediate value 0x2a is being stored at the location stored in the EAX register, using X86 assembly language. This is an example of register indirect addressing.Printing the low order bits of the address shows that it is not aligned to lớn a word boundary ("dword" using x86 terminology). Segmentation fault exampleHere is an example of ANSI C code that should create a segmentation fault on platforms with memory protection: int main(void) char *s = "hello world"; *s = "H"; When the program containing this code is compiled, the string "hello world" is placed in the section of the program binary marked as read-only; when loaded, the operating system places it with other strings & constant data in a read-only segment of memory. When executed, a variable, s, is phối lớn point to lớn the string"s location, và an attempt is made to lớn write an H character through the variable into lớn the memory, causing a segmentation fault. Compiling such a program with a compiler that does not kiểm tra for the assignment of read-only locations at compile time, & running it on a Unix-lượt thích operating system produces the following runtime error:$ 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 khổng lồ an operating system.Because a very comtháng program error is a null pointer dereference (a read or write through a null pointer, used in C to lớn mean "pointer khổng lồ no object" and as an error indicator), most operating systems bản đồ 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, và tries lớn assign a value to lớn 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 stachồng to overflow which results in a segmentation fault.
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A segmentation fault occurs when a program attempts to access a memory location that it is not allowed khổng lồ access, or attempts khổng lồ access a memory location in a way that is not allowed (for example, attempting lớn write to a read-only location, or khổng lồ 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 màn chơi 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. Comtháng causesA few causes of a segmentation fault can be summarized as follows: * attempting lớn exedễ thương a program that does not compile correctly. cảnh báo that most compilers will not output a binary given a compile-time error. * a buffer overflow. * using uninitialized pointers. * dereferencing NULL pointers. * attempting lớn access memory the program does not own. * attempting to alter memory the program does not own (storage violation).Generally, segmentation faults occur because: a pointer is either NULL, points to random memory (probably never initialized lớn anything), or points to lớn memory that has been freed/deallocated/"deleted".e.g. char *p1 = NULL; // Initialized lớn 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 $0x40000,(%rsp) popf");# endif#endif /* malloc() always provides aligned memory */ cptr = malloc(sizeof(int) + 1); /* Increment the pointer by one, making it misaligned */ iptr = (int *) ++cptr; /* Dereference it as an int pointer, causing an unaligned access */ *iptr = 42; return 0;Compiling & running the example on Linux on x86 demonstrates the error:$ gcc -ansay mê sigbus.c -o sigbus$ ./sigbus Bus error$ gdb ./sigbus(gdb) rProgram received signal SIGBUS, Bus error.0x080483tía in main ()(gdb) x/i $pc0x80483ba : mov DWORD PTR ,0x2a(gdb) p/x $eax$1 = 0x804a009(gdb) p/t $eax và (sizeof(int) - 1)$2 = 1The GDB debugger shows that the immediate value 0x2a is being stored at the location stored in the EAX register, using X86 assembly language. This is an example of register indirect addressing.Printing the low order bits of the address shows that it is not aligned to lớn a word boundary ("dword" using x86 terminology). Segmentation fault exampleHere is an example of ANSI C code that should create a segmentation fault on platforms with memory protection: int main(void) char *s = "hello world"; *s = "H"; When the program containing this code is compiled, the string "hello world" is placed in the section of the program binary marked as read-only; when loaded, the operating system places it with other strings & constant data in a read-only segment of memory. When executed, a variable, s, is phối lớn point to lớn the string"s location, và an attempt is made to lớn write an H character through the variable into lớn the memory, causing a segmentation fault. Compiling such a program with a compiler that does not kiểm tra for the assignment of read-only locations at compile time, & running it on a Unix-lượt thích operating system produces the following runtime error:$ 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 khổng lồ an operating system.Because a very comtháng program error is a null pointer dereference (a read or write through a null pointer, used in C to lớn mean "pointer khổng lồ no object" and as an error indicator), most operating systems bản đồ 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, và tries lớn assign a value to lớn 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 stachồng to overflow which results in a segmentation fault.
