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Casting the result of malloc() to the appropriate pointer type enables the compiler to catch subsequent inadvertent pointer conversions. When allocating individual objects, the "appropriate pointer type" is a pointer to the type argument in the sizeof expression passed to malloc(), as in. This approach is applied in the following code example:

widget *p;

/* ... */

p = (gadget *)malloc(sizeof(gadget)); /* invalid assignment */

Here, malloc() allocates space for a gadget and the cast immediately converts the returned pointer to a gadget *. This lets the compiler detect the invalid assignment, because it attempts to convert a gadget * into a widget *. The problem can now be easily identified and corrected:

widget *p;

/* ... */

p = (widget *)malloc(sizeof(widget)); /* invalid assignment */

Compliant Solution

Repeating the same type in the sizeof expression and the pointer cast is easy to do, but still invites errors. Packaging the repetition in a macro, such as

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