Frequently encountered errors

I gave a brief explanation HERE.
Need more, eventually snippet code, examples, demo application? ;)

Quote:

---

Originally Posted by Skoons

You will never belive but some years ago I have found something like this in project which was on last test before release :eek:

Code:

---

  p=malloc(bytes);
  if(p==NULL)
    {
      ShowMessage("Can`t allocate enough memory");
      exit(EXIT_FAILURE);
      }

---

So this software (it was written on C language as you see) if can`t find some more bytes for new data object closed itself, and even not ask user to save his work.

---

That is not because it contains only valid C code that it was written in C (of course, you have seen the true project, so, you know).

I just quoted your text to introduce the fact I found some "apparently C codes" which revealed, after a further examination, to be C++ (pass by references used somewhere for example).

I have often seen this which can lead to problems:

if(result = DoSomeStuff( data))
{
...
}

And this is common for beginners and is particularly hard to find in order to fix:

if(this = that)
{
do_stuff();
}

Being as 'this' will become 'that' and will always equal that. So this conditional will always be true.

Maybe not a 'beginners' error:

if(object->next->value == value)
{
do_stuff();
}

When there is no reason to assume that the 'next' object actually exists...

:cool:

Quote:

---

Originally Posted by Zorro3D

I have often seen this which can lead to problems:

if(result = DoSomeStuff( data))
{
...
}

---

You can make it clearer by saying
if ( ( result = DoSomeStuff( data ) ) != 0 )
{
...
}

I have been known not to bother to put the !=0 comparison it. It's usually obvious that you are intending to assign result and continue into the block if it's non-zero.

Quote:

---

And this is common for beginners and is particularly hard to find in order to fix:

if(this = that)
{
do_stuff();
}

Being as 'this' will become 'that' and will always equal that. So this conditional will always be true.

---

won't compile. this is not an l-value.

Quote:

---

Maybe not a 'beginners' error:

if(object->next->value == value)
{
do_stuff();
}

When there is no reason to assume that the 'next' object actually exists...

:cool:

---

and if this is done in C++ it's a beginners error to be using their own list and not std::list and algorithms. In fact it's a beginners error to use linear search in situations where either std::map or a sorted vector would be a better idea.

I go crazy when I see something like this:

Code:

---

#define AFUNC1(a, b)  AFunc(a, b)
#define AFUNC2(a)  AFunc(a, NULL)

void AFunc(int a, const char* b)
{
 // don something
}

...
AFUNC2(10);

---

And I've seen code like that.

And I wish I had a gun when I see things like this:

Code:

---

#include <iostream>

using namespace std;

#define BEGIN          \
  if(index<0 || index>=5)    \
    return;          \
  goo temp = _goo[index];    \
  temp.Init();        \
 
#define END            \
  temp.Close();

class goo
{
public:
  goo(){}
  goo(const goo& cpy) {}
  const goo& operator=(const goo& rval) {  return *this;}
  void Init() { cout << "goo::init" << endl;}
  void Action() {cout << "goo::action" << endl;}
  void Reaction() {cout << "goo::reaction" << endl;}
  void Close() {cout << "goo::close" << endl;}
};

class foo
{
  goo *_goo;
public:
  foo();
  ~foo();
  void do_something(int index);
  void do_something_else(int index);
};

foo::foo()
{
  _goo = new goo[5];
}

foo::~foo()
{
  delete [] _goo;
}

void foo::do_something(int index)
{
  BEGIN 
  temp.Action();
  END
}

void foo::do_something_else(int index)
{
  BEGIN
  temp.Reaction();
  END
}

int main()
{
  foo f;
  f.do_something(0);
  f.do_something_else(4);

  return 0;
}

---

What do you think? This one...

Code:

---

  for(int i = 0; i < nCount; i++)
  {
      try
      {
        // something...
      }
      catch(...)
      {
        i --; // try again
      }
  }

---

... could be funny, stupid, or it's really a bad joke?