C++中段错误的常见情况

Program terminated with signal 11, Segmentation fault.

空指针访问非虚函数

include <iostream>
class Foo
{
public:
  Foo() : a(0) {}
  void Bar() { std::cout << "Bar:" << a << std::endl; }
private:
  int a;
};
int main() {
  Foo* f = NULL;
  f->Bar();
  std::cout << "hello" << std::endl;
  return 0;
}

(gdb) bt
#0  0x00000000004008ef in Foo::Bar (this=0x0) at null.cpp:6
#1  0x00000000004008bb in main () at null.cpp:14
(gdb)

空指针访问虚函数

#include <iostream>
class Foo
{
public:
  Foo() : a(0) {}
  virtual void Bar() { std::cout << "Bar:" << a << std::endl; }
private:
  int a;
};

int main() {
  Foo* f = NULL;
  f->Bar();
  std::cout << "hello" << std::endl;
  return 0;
}

(gdb) bt
#0  0x0000000000400866 in main () at null.cpp:14
(gdb) p f
$1 = (Cannot access memory at address 0x0

野指针访问虚函数

#include <iostream>
class Foo
{
public:
  Foo() : a(0) {}
  virtual void Bar() { std::cout << "Bar:" << a << std::endl; }
private:
  int a;
};

int main() {
  Foo* f = new Foo();
  delete f;
  f->Bar();
  std::cout << "hello" << std::endl;
  return 0;
}

(gdb) bt
#0  0x00000000004009c4 in main () at null.cpp:15
(gdb) p f
$1 = (Foo *) 0x602010