Об отладке программ МО ВВС ИВМ и МГ СО РАН Городничев Максим Александрович

Отладочный вывод Буферизованный вывод printf(“Программа пришла сюда\n”); std::cout << “Текст\n” Небуферизованный вывод fprintf(stderr, “Программа пришла сюда\n”); std::cerr << “Текст\n”;

Отладочный вывод Очистка буфера: Cprintf(“Text\n”); fflush(stdout); C++std::cout << “Text\n”; std::cout.flush();

Отладка в gdb. Пример ошибочной программы. #include int f() { int* p = 0; *p = 100; return *p; } void g() { printf("%d", f()); } int main() { g(); } tests]$./a.out Segmentation fault

Отладка в gdb. Компиляция. tests]$ gcc –g3 segfault.c

Отладка в gdb. Запуск программы в отладчике. tests]$ gdb./a.out GNU gdb 6.6 Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-suse-linux"... Using host libthread_db library "/lib/libthread_db.so.1". (gdb) run

Отладка программы в gdb. Анализ ошибки Starting program: /home/maxim/work/tests/a.out Program received signal SIGSEGV, Segmentation fault. 0x in f () at segfault.c:5 5 *p = 100; (gdb) backtrace #0 0x in f () at segfault.c:5 #1 0x c in g () at segfault.c:11 #2 0x080483a4 in main () at segfault.c:16 (gdb) print p $1 = (int *) 0x0 (gdb) quit The program is running. Exit anyway? (y or n) y

Отладка в gdb. Пошаговое выполнение. (gdb) break g Breakpoint 1 at 0x : file segfault.c, line 11. (gdb) run Starting program: /home/maxim/work/tests/a.out warning:.dynamic section for "/lib/libc.so.6" is not at the expected address warning: difference appears to be caused by prelink, adjusting expectations Breakpoint 1, g () at segfault.c:11 11 printf("%d", f()); (gdb) next Program received signal SIGSEGV, Segmentation fault. 0x in f () at segfault.c:5 5 *p = 100;

Отладка в gdb. Пошаговое выполнение. (gdb) step f () at segfault.c:4 4 int* p = 0; (gdb) list 1 #include 2 int f() 3 { 4 int* p = 0; 5 *p = 100; 6 return *p; 7 } 8 9 void g() 10{ (gdb) continue

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