On 11/24/2010 07:27 PM, Anthony Liguori wrote:
The alternative in C is:
struct file_operations {
void (*release)(void);
void (*read)(...);
void (*write)(...);
};
struct file {
struct file_operations *ops;
};
If I do:
static file_operations posix_file_ops = {
.read = posix_file_read,
.write = posix_file_write,
};
struct posix_file {
struct file parent;
int fd;
};
void posix_file_init(struct posix_file *obj)
{
obj->parent.ops = posix_file_ops;
obj->fd = ...;
};
The compiler won't generate an error. Only upon a call to
file_release() will a null pointer dereference happens whereas in C++,
because this paradigm is structured in the language, the compiler can
help assist you.
You forgot to mention:
static void posix_file_read(struct file *_file, ...)
{
struct posix_file *file = container_of(_file, struct posix_file,
parent);
...
}
Even more boilerplate and potential for error. But I think the worst
thing about this is that it makes it hard to do the right thing, so
people hack quick and dirty workarounds. C++ makes this pattern trivial
(if : laden), so people are encouraged to use it.
--
error compiling committee.c: too many arguments to function
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