The __nocast attribute

    void *kmalloc(size_t size, unsigned int __nocast flags);

For normal compilation, this attribute expands to an empty string; it has no effect. When the sparse tool is being used, however, the __nocast attribute disables many of the implicit type conversions performed by the compiler. In the kmalloc() case, sparse will complain whenever a signed integer value is passed as the flags argument. Since the GFP flags passed to kmalloc() are explicitly defined as unsigned values, they will not cause a warning to be issued. Any normal integer variable or constant, however, will be flagged. Similarly, the use of an integer value where an enumerated type is expected will be caught. Thus, this little tweak should help with the automated detection of another class of errors that the compiler will not find.