CODEWITHSUNDEEP
c++
Tom
Tom

Reputation: 1394

Is it accurate to say that C++ is a partially type safe language?

There are some features in C++ that are type safe and some other features that are not.

Example of C++ type safety:

char c = 'a';
int *p = &c;    // this is not allowed (compiler error)

Example of C++ lack of type safety:

int *p;        // I don't have to initialize p, and so it will have some junk/random value
*p = 12345;    // this will probably lead to segmentation fault!

I have read in a couple of articles that C++ is not a type safe language. Can I consider it to be a non type safe language, or is it more accurate to say that it is a partially type safe language?

Upvotes: 3

Views: 1343

Answers (2)

Galik
Galik

Reputation: 48615

The example you are giving is not violating "type safety" at all. Here:

Example of C++ lack of type safety:

int *p;     // I don't have to initialize p, and so it will have some junk/random value
*p = 12345; // this will probably lead to segmentation fault!

In that example *p is an int and you are assigning it the number 12345 which is also an int.

The compiler is not allowing you to violate the type system because you are assigning one int to another int.

The fact that the pointer you are dereferencing to get to one of your ints is not initialized is causing a potential crash but it has nothing to do with type safety.

This will not crash:

int* p = new int;
*p = 12345;

Here you are writing an int (12345) to another int (*p) but this time the int you are writing to (*p) actually exists.

It is not type safety that the compiler is failing to check it is the integrity of the pointer.

Upvotes: 2

Cheers and hth. - Alf
Cheers and hth. - Alf

Reputation: 145259

It's reasonable and practically meaningful to say that C++ is a partially type safe language.

C++ started as an extension of original mid- to late 1970's C, which was designed as a kind of high level portable assembly language, to make Unix more portable and easier to maintain. C++ added type safety for its new features, but with the goal of being mainly compatible with C (in particular using all those existing C libraries, including their headers) the original core of C had to be left as it was.

In particular, C++ got the decay of array to pointer from C. In C++ it isn't type safe because it allows an implicit conversion from array of Derived to pointer to Base, which can in turn be indexed but with Undefined Behavior.

Upvotes: 2

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