Why Must I Cast the Return Value of `malloc()` in C , but Not in C?

Understanding the Cast Requirement for malloc() in C

In C , developers must cast the return value of malloc() to the intended pointer type, while in C, this cast is not required. This distinction stems from several key differences between the two languages.

In C, void pointers can be implicitly converted to any other object pointer type, a feature not present in C . This allows C programmers to assign the return value of malloc() (which returns a void pointer) directly to a specific pointer type without an explicit cast.

However, in C , casting is necessary due to the strict type system that enforces compatibility between variables and their assigned values. Without a cast, the compiler cannot ensure that the return value from malloc() (a void pointer) is suitable for assignment to a variable of a specific pointer type.

Furthermore, casting the result of malloc() in C serves as a diagnostic tool. Without the cast, if a declaration for malloc() is missing in scope, the compiler interprets the call as returning an int instead of a pointer, leading to a type incompatibility diagnostic. The cast suppresses this diagnostic, removing a potential source of runtime issues.

While malloc() and free() can be used in C , it is generally advisable to utilize the language-specific memory management tools, new and delete, rather than relying on C legacy functions. This approach aligns with the best practices for writing idiomatic C code.

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