Messages in this thread | | | Date | Mon, 12 Mar 2007 13:37:43 +0800 | From | "Cong WANG" <> | Subject | Re: Style Question |
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2007/3/12, Jan Engelhardt <jengelh@linux01.gwdg.de>: > > On Mar 11 2007 22:15, Cong WANG wrote: > > > > I have a question about coding style in linux kernel. In > > Documention/CodingStyle, it is said that "Linux style for comments is > > the C89 "/* ... */" style. Don't use C99-style "// ..." comments." > > _But_ I see a lot of '//' style comments in current kernel code. > > > > Which is wrong? The documentions or the code, or neither? And why? > > The code. And because it's not always reviewed but silently pushed. > > > Another question is about NULL. AFAIK, in user space, using NULL is > > better than directly using 0 in C. In kernel, I know it used its own > > NULL, which may be defined as ((void*)0), but it's _still_ different > > from raw zero. > > In what way?
The following code is picked from drivers/kvm/kvm_main.c:
static struct kvm_vcpu *vcpu_load(struct kvm *kvm, int vcpu_slot) { struct kvm_vcpu *vcpu = &kvm->vcpus[vcpu_slot];
mutex_lock(&vcpu->mutex); if (unlikely(!vcpu->vmcs)) { mutex_unlock(&vcpu->mutex); return 0; } return kvm_arch_ops->vcpu_load(vcpu); }
Obviously, it used 0 rather than NULL when returning a pointer to indicate an error. Should we fix such issue?
> > >So can I say using NULL is better than 0 in kernel? > > On what basis? Do you even know what NULL is defined as in > (C, not C++) userspace? Think about it. >
I think it's more clear to indicate we are using a pointer rather than an integer when we use NULL in kernel. But in userspace, using NULL is for portbility of the program, although most (*just* most, NOT all) of NULL's defination is ((void*)0). ;-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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