Why are pointers not recommended when coding with C++?

Question

I read from somewhere that when using C++ it is recommended not to use pointers. Why is pointers such a bad idea when you are using C++. For C programmers that are used to using pointers, what is the better alternative and approach in C++?

Answer 1

I think they mean you should use smart pointers instead of regular pointers.

In computer science, a smart pointer is an abstract data type that simulates a pointer while providing additional features, such as automatic garbage collection or bounds checking. These additional features are intended to reduce bugs caused by the misuse of pointers while retaining efficiency. Smart pointers typically keep track of the objects they point to for the purpose of memory management.

The misuse of pointers is a major source of bugs: the constant allocation, deallocation and referencing that must be performed by a program written using pointers introduces the risk that memory leaks will occur. Smart pointers try to prevent memory leaks by making the resource deallocation automatic: when the pointer (or the last in a series of pointers) to an object is destroyed, for example because it goes out of scope, the pointed object is destroyed too.

In C++ the emphasis would be on garbage collection and preventing memory leaks (just to name two). Pointers are a fundamental part of the language, so not using them is pretty much impossible except in the most trival of programs.

Answer 2

Since I’m the one who published the polemic “don’t use f*cking pointers” I feel that I should comment here.

First of all, as a polemic it obviously represents an extreme viewpoint. There are definitely legitimate uses of (raw, and other) pointers. But I (and many professional C++ programmers) maintain that pointers in C++ are vastly overused. But what we really mean is the following:

First:

Raw pointers must under no circumstances own memory.

Here, “own memory” essentially means that at some point delete is called on that pointer (but it’s more general than that). This statement can safely be taken as an absolute. The only exception is when implementing your own smart pointer (or other memory management strategy). And even there you should normally still use a smart pointer at low level.

The rationale for this is quite simple: raw pointers which own memory introduce a source of error. And these errors are prolific in existing software: memory leaks and double deletion – both a direct consequence of unclear resource ownership (but going in opposite direction).

This problem can be entirely eliminated, at virtually no cost, by simply using smart pointers instead of raw pointers (caveat: this still requires thinking, of course; shared pointers can lead to cycles and thus once again to memory leaks – but this is easily avoidable).

Second:

Most uses of pointers in C++ are unnecessary.

Unlike other languages, C++ has very strong support for value semantics and simply doesn’t need the indirection of pointers. This wasn’t immediately realised – historically, C++ was invented to facilitate easy object orientation in C, and relied heavily on constructing object graphs which were connected by pointers. But in modern C++, this paradigm is rarely the best choice, and modern C++ idioms often don’t need pointers at all. They operate on values rather than pointers.

Unfortunately, this message has still not caught on in large parts of the C++ user community. As a result, most of the C++ code that is written is still littered with superfluous pointers which make the code complex, slow and faulty / unreliable.

For somebody who knows modern C++, it’s clear that you very rarely need any pointers (either smart or raw; except when using them as iterators). The resulting code is shorter, less complex, more readable, often more efficient and more reliable.

Answer 3

Simply because there are abstractions available to your which hide the more temperamental aspects of using pointers, such as access to raw memory and cleaning up after your allocations. With smart pointers, container classes, and design patterns like RAII, the need for using raw pointers is diminished. That said, like any abstraction, you should understand how they actually work before moving beyond them.

Answer 4

Relatively simply, the C mentality is "Got a problem? Use a pointer". You can see this in C strings, function pointers, pointers-as-iterators, pointer-to-pointer, void pointer- even in the early days of C++ with member pointers.

But in C++ you can use values for many or all of these tasks. Need a function abstraction? std::function. It's a value that's a function. std::string? It's a value, that's a string. You can see similar approaches all over C++. This makes analyzing the code vastly easier for both humans and compilers.

Answer 5

One of reasons is too wide application of pointers. They can be used for iteration over containers, for avoiding copying large objects when passing to function, non-trivial life-time management, accessing to random places in memory, etc. And once you used them for one purpose, other their features become available immediately independently on intent.

Selection of a tool for exact purpose makes code simpler and intent more visible - iterators for iterations, smart pointers for life-time management, etc.

Answer 6

Besides the reasons already listed, there is an obvious one: better optimisations. Aliasing analysis is far too complicated in presense of a pointer arithmetics, whereas references hints an optimiser, so a much deeper aliasing analysis is possible if only references are used.

Answer 7

Beside the risk of memory leaks stated by @jmquigley pointer and pointer arithmetic can be considered problematic because pointers can point everywhere in memory causing "hard to find bugs" and "security vulnerableties".

That is why they were nearly abandoned in C# and Java.

Answer 8

C++ supports most of C, features, plus Objects and Classes. C already had pointers and other stuff.

Pointers are a very useful technique, that can be combined with Object Orientation, and C++ supports them. But, this technique, is difficult to teach and difficult to understand, and, its very easy to cause unwanted errors.

Many new programming languages pretend not to use pointers with objects, like Java, .NET, Delphi, Vala, PHP, Scala. But, pointers are still used, "behind the scenes". These "hidden pointer" techniques are called "references".

Anyway, I consider pointer (s) as a Programming Pattern, as a valid way to solve certain problems, as well as Object Oriented Programming does.

Other developers may have a different opinion. But, I suggest students and programmers learn how to:

(1) Use pointers without objects

(2) objects without pointers

(3) explicit pointers to objects

(4) "hidden" pointers to objects ( A.K.A. reference) ;-)

In that order.

Even if is difficult to teach, and difficult to learn. Object Pascal (Delphi, FreePascal, others) and C++ (not Java or C#) can be used for those goals.

And, later, novice programmers, can move to "hidden pointers to objects" programming languages like: Java, C#, Object Oriented PHP, and others.

Answer 9

Talking about VC6, when you cast a pointer of a class (that you instantiate) into a variable (e.g. DWORD), even if this pointer is local you can access the class over all the functions that use the same heap. The instantiated class is defined as local but in fact it is not. As far as I know, any address of a heap variable, structure or class is unique along all the life of the hosting class.

Example:

class MyClass1 { public: void A (void); void B (void); void C (void); private: DWORD dwclass; }; class MyClass2 { public: int C (int i); }; void MyClass1::A (void) { MyClass2 *myclass= new MyClass2; dwclass=(DWORD)myclass; } void MyClass1::B (void) { MyClass2 *myclass= (MyClass2 *)dwclass; int i = myclass->C(0); // or int i=((MyClass2 *)dwclass)->C(0); } void MyClass1::B (void) { MyClass2 *myclass= (MyClass2 *)dwclass; delete myclass; } 

EDIT Thats a very little part of the original code. The CSRecodset class is only a casting class of CXdbRecordset, where all the real code is. Doing so I can let the user take benefit of what I wrote without loosing my rights. I do not pretend to demonstrate that my database engine is professional but it really works.

//------------------------------------- class CSRecordSet : public CSObject //------------------------------------- { public: CSRecordSet(); virtual ~CSRecordSet(); // Constructor bool Create(CSDataBase* pDataBase,CSQueryDef* pQueryDef); //Open, find, close int OpenRst(bool bReadBlanks=0,bool bCheckLastSql=0,bool bForceLoad=0,bool bMessage=1); // for a given SQL int FindRecord(bool bNext); // for a given SQL // TABLE must be ordered by the same fields that will be seek bool SeekRecord(int nFieldIndex, char *key, int length=0); // CRT bsearch bool SeekRecord(int nFieldIndex, long key); bool SeekRecord(int nFieldIndex, double key, int decimals); bool SeekRecord(XSEK *SEK); bool DeleteRecord(void); bool Close(void); // Record Position: bool IsEOF(void); // pointer out of bound bool IsLAST(void); // TRUE if last record bool IsBOF(void); // pointer out of bound bool IsOpen(void); bool Move(long lRows); // returns FALSE if out of bound void MoveNextNotEof(void); // eof is tested void MoveNext(void); // eof is not tested void MovePrev(void); // bof is tested void MoveLast(void); void MoveFirst(void); void SetAbsolutePosition(long lRows); long GetAbsolutePosition(void); void GoToLast(void); // Restore position after a Filter // Table info long GetRecordCount(void); int GetRstTableNumber(void); int GetRecordLength(void); //includes stamp (sizeof char) int GetTableType(void); // Field info int GetFieldCount(void); void GetFieldName(int nFieldIndex, char *pbuffer); int GetFieldIndex(const char *sFieldName); int GetFieldSize(int nFieldIndex); int GetFieldDGSize(int nFieldIndex); // String size (i.e. dg_Boolean) long GetRecordID(void); int GetStandardFieldCount(void); bool IsMemoFileTable(void); bool IsNumberField(int nFieldIndex); int GetFieldType(int nFieldIndex); // Read Field value bool GetFieldValue(int nFieldIndex, XdbVar& var); bool GetFieldValueIntoBuffer(int nFieldIndex,char *pbuffer); char *GetMemoField(int nMemoFieldIndex, char *pbuffer, int buf_size); bool GetBinaryField(unsigned char *buffer,long *buf_size); // Write Field value void Edit(void); // required bool SetFieldValue(int nFieldIndex, XdbVar& var); bool SetFieldValueFromBuffer(int nFieldIndex,const char *pbuffer); bool Update(void); // required // pointer to the same lpSql LPXSQL GetSQL(void); }; //--------------------------------------------------- CSRecordSet::CSRecordSet(){ //--------------------------------------------------- pClass |= (CS_bAttach); } CSRecordSet::~CSRecordSet(){ if(pObject) delete (CXdbRecordset*)pObject; } bool CSRecordSet::Create(CSDataBase* pDataBase,CSQueryDef* pQueryDef){ CXdbQueryDef *qr=(CXdbQueryDef*)pQueryDef->GetObject(); CXdbTables *db=(CXdbTables*)pDataBase->GetObject(); CXdbRecordset *rst = new CXdbRecordset(db,qr); if(rst==NULL) return 0; pObject = (unsigned long) rst; return 1; } bool CSRecordSet::Close(void){ return ((CXdbRecordset*)pObject)->Close(); } int CSRecordSet::OpenRst(bool bReadBlanks,bool bCheckLastSql,bool bForceLoad, bool bMessage){ unsigned long dw=0L; if(bReadBlanks) dw|=SQL_bReadBlanks; if(bCheckLastSql) dw|=SQL_bCheckLastSql; if(bMessage) dw|=SQL_bRstMessage; if(bForceLoad) dw|=SQL_bForceLoad; return ((CXdbRecordset*)pObject)->OpenEx(dw); } int CSRecordSet::FindRecord(bool bNext){ return ((CXdbRecordset*)pObject)->FindRecordEx(bNext); } bool CSRecordSet::DeleteRecord(void){ return ((CXdbRecordset*)pObject)->DeleteEx(); } bool CSRecordSet::IsEOF(void){ return ((CXdbRecordset*)pObject)->IsEOF(); } bool CSRecordSet::IsLAST(void){ return ((CXdbRecordset*)pObject)->IsLAST(); } bool CSRecordSet::IsBOF(void){ return ((CXdbRecordset*)pObject)->IsBOF(); } bool CSRecordSet::IsOpen(void){ return ((CXdbRecordset*)pObject)->IsOpen(); } bool CSRecordSet::Move(long lRows){ return ((CXdbRecordset*)pObject)->MoveEx(lRows); } void CSRecordSet::MoveNextNotEof(void){ ((CXdbRecordset*)pObject)->MoveNextNotEof(); } void CSRecordSet::MoveNext(void){ ((CXdbRecordset*)pObject)->MoveNext(); } void CSRecordSet::MovePrev(void){ ((CXdbRecordset*)pObject)->MovePrev(); } void CSRecordSet::MoveLast(void){ ((CXdbRecordset*)pObject)->MoveLast(); } void CSRecordSet::MoveFirst(void){ ((CXdbRecordset*)pObject)->MoveFirst(); } void CSRecordSet::SetAbsolutePosition(long lRows){ ((CXdbRecordset*)pObject)->SetAbsolutePosition(lRows); } long CSRecordSet::GetAbsolutePosition(void){ return ((CXdbRecordset*)pObject)->m_AbsolutePosition; } long CSRecordSet::GetRecordCount(void){ return ((CXdbRecordset*)pObject)->GetRecordCount(); } int CSRecordSet::GetFieldCount(void){ return ((CXdbRecordset*)pObject)->GetFieldCount(); } int CSRecordSet::GetRstTableNumber(void){ return ((CXdbRecordset*)pObject)->GetRstTableNumber(); } void CSRecordSet::GetFieldName(int nFieldIndex, char *pbuffer){ ((CXdbRecordset*)pObject)->GetFieldName(nFieldIndex,pbuffer); } int CSRecordSet::GetFieldIndex(const char *sFieldName){ return ((CXdbRecordset*)pObject)->GetFieldIndex(sFieldName); } bool CSRecordSet::IsMemoFileTable(void){ return ((CXdbRecordset*)pObject)->IsMemoFileTable(); } bool CSRecordSet::IsNumberField(int nFieldIndex){ return ((CXdbRecordset*)pObject)->IsNumberField(nFieldIndex); } bool CSRecordSet::GetFieldValueIntoBuffer(int nFieldIndex,char *pbuffer){ return ((CXdbRecordset*)pObject)->GetFieldValueIntoBuffer(nFieldIndex,pbuffer); } void CSRecordSet::Edit(void){ ((CXdbRecordset*)pObject)->Edit(); } bool CSRecordSet::Update(void){ return ((CXdbRecordset*)pObject)->Update(); } bool CSRecordSet::SetFieldValue(int nFieldIndex, XdbVar& var){ return ((CXdbRecordset*)pObject)->SetFieldValue(nFieldIndex,var); } bool CSRecordSet::SetFieldValueFromBuffer(int nFieldIndex,const char *pbuffer){ return ((CXdbRecordset*)pObject)->SetFieldValueFromBuffer(nFieldIndex,pbuffer); } bool CSRecordSet::GetFieldValue(int nFieldIndex, XdbVar& var){ return ((CXdbRecordset*)pObject)->GetFieldValue(nFieldIndex,var); } bool CSRecordSet::SeekRecord(XSEK *SEK){ return ((CXdbRecordset*)pObject)->TableSeek(SEK); } bool CSRecordSet::SeekRecord(int nFieldIndex,char *key, int length){ return ((CXdbRecordset*)pObject)->TableSeek(nFieldIndex,key,length); } bool CSRecordSet::SeekRecord(int nFieldIndex,long i){ return ((CXdbRecordset*)pObject)->TableSeek(nFieldIndex,i); } bool CSRecordSet::SeekRecord(int nFieldIndex, double d, int decimals) { return ((CXdbRecordset*)pObject)->TableSeek(nFieldIndex,d,decimals); } int CSRecordSet::GetRecordLength(void){ return ((CXdbRecordset*)pObject)->GetRecordLength(); } char *CSRecordSet::GetMemoField(int nMemoFieldIndex,char *pbuffer, int BUFFER_SIZE){ return ((CXdbRecordset*)pObject)->GetMemoField(nMemoFieldIndex,pbuffer,BUFFER_SIZE); } bool CSRecordSet::GetBinaryField(unsigned char *buffer,long *buf_size){ return ((CXdbRecordset*)pObject)->GetBinaryField(buffer,buf_size); } LPXSQL CSRecordSet::GetSQL(void){ return ((CXdbRecordset*)pObject)->GetSQL(); } void CSRecordSet::GoToLast(void){ ((CXdbRecordset*)pObject)->GoToLast(); } long CSRecordSet::GetRecordID(void){ return ((CXdbRecordset*)pObject)->GetRecordID(); } int CSRecordSet::GetStandardFieldCount(void){ return ((CXdbRecordset*)pObject)->GetStandardFieldCount(); } int CSRecordSet::GetTableType(void){ return ((CXdbRecordset*)pObject)->GetTableType(); } int CSRecordSet::GetFieldType(int nFieldIndex){ return ((CXdbRecordset*)pObject)->GetFieldType(nFieldIndex); } int CSRecordSet::GetFieldDGSize(int nFieldIndex){ return ((CXdbRecordset*)pObject)->GetFieldDGSize(nFieldIndex); } int CSRecordSet::GetFieldSize(int nFieldIndex){ return ((CXdbRecordset*)pObject)->GetFieldSize(nFieldIndex); } 

EDIT: requested by DeadMG:

void nimportequoidumomentquecaroule(void) { short i = -4; unsigned short j=(unsigned short)i; }