Casting malloc and calloc in C and C++

Implicit Conversion in C

In C, it’s not necessary to cast the result of a call to calloc() or malloc(). This is because you can implicitly convert a void * to any other pointer type. Here’s how you can do it:

int* ptr_calloc = calloc(5, sizeof(int));
int* ptr_malloc = malloc(5 * sizeof(int));

Typecasting in C++

However, this implicit conversion is not allowed in C++. Therefore, in C++ you would need to cast the result of calloc() or malloc().

int* ptr_calloc = (int*) calloc(5, sizeof(int));
int* ptr_malloc = (int*) malloc(5 * sizeof(int));

C and C++ Compatibility

This cast is often done when writing code that’s intended to be compiled as either C or C++. However, this is generally not recommended. C++ has new and delete operators for dynamic memory allocation which are safer and more feature-rich.

Preferred Dynamic Memory Allocation in C++

In C++, it’s more common to use new and delete for dynamic memory allocation and deallocation. This handles object creation and destruction, works with classes and inheritance, and helps prevent common memory issues.

int* ptr = new int[5];
// Use ptr...
delete[] ptr;

Potential Issues with Casting in C

Casting the result of calloc() or malloc() in C can mask a failure to include stdlib.h, where calloc() and malloc() are declared. Without the include, and without a cast, the compiler would issue a warning or error. With the cast, this important message can be suppressed.

Recommendation

It’s generally advised not to cast the result of calloc() or malloc() in C code as it is unnecessary and could potentially conceal a bug.