一些有意思，有深度，容易错的代码收集

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一些有意思，有容易错误的代码，下面列了几个，其他的参见上述的网址

/*
* main.cpp
*
*  Created on: Mar 5, 2016
*      Author: xiaophuang
*/
#include <vector>
#include <iostream>

using namespace std;

/* This one may well work with some compilers/OS, and crash with
others. Who said the STL was safe ?? */

int main()
{
vector<int> v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
for (vector<int>::iterator i = v.begin();i != v.end(); i++)
{
cout << *i << endl;
if (*i == 1)
{
v.push_back(5);
}
}
}

#include <stdio.h>
#include <limits.h>

void compare (int a) {
if ((a+1) > a)
printf("%d > %d\n", (a+1), a);
else
printf("%d <= %d\n", (a+1), a);
}

int main () {
/*
* When compiled with gcc -O0, I get different results for
* both lines. With gcc -O1, I get the same. When compiling
* with clang, I even more surprising results.
*
* Surprisingly (or not), these results do not correspond to
* bugs in the compilers.
*
* The warning given by both compilers helps understanding
* what's going on, but I had to read the standard to really
* get it.
*/
int i = 33;
printf("%d\n", 1 << 33);
printf("%d\n", 1 << i);

/*
* adapted from http://blog.regehr.org/archives/213 *
* Try compiling this with -O0 and with -O3, and see ...
* Again, no compiler bug involved!
*/
compare(1);
compare(INT_MAX);
}

#include <iostream>

using namespace std;

struct B {
virtual void whoami () const
{cout << "B" << endl;}
};

struct D : public B {
void whoami ()
{cout << "D" << endl;}
};

int main() {
D d;
B *b = &d;
b->whoami();　 // B
D *dd = &d;
dd->whoami();  //D
}