Re: [libvirt] [PATCH 04/11] qemu_security: Kill code duplication
On Wed, Feb 08, 2017 at 14:37:48 +0100, Michal Privoznik wrote:
On 02/08/2017 01:43 PM, Peter Krempa wrote:
> On Wed, Feb 08, 2017 at 13:37:48 +0100, Michal Privoznik wrote:
>> On 02/08/2017 01:23 PM, Peter Krempa wrote:
>>> On Wed, Feb 08, 2017 at 11:37:07 +0100, Michal Privoznik wrote:
>>>> Nearly all of these functions look the same. Except for a
>>>> different virSecurityManager API call. There is no need to copy
>>>> paste the code when we can use macros to generate it.
>>>>
>>>> Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
>>>> ---
>>>> src/qemu/qemu_security.c | 179
++++++++++++-----------------------------------
>>>> 1 file changed, 44 insertions(+), 135 deletions(-)
>>>
>>> NACK, please don't partialy define function with macros.
>>>
>>
>> Why not? What is the downside?
>
> You'll never be able to navigate to the body of the function or ever
> find it try 'vim -t qemuSecurityRestoreHostdevLabel' or navigate to
> that after that patch.
I don't think this is ultimate goal. A lot of our code is written in a
callback style: var->cb(blaah). You cannot jump to the actual function
either. If doing 'vim -t' is the ultimate goal then we should ban
callbacks too.
Callbacks are way different from this case. Even if you have a callback
then a debugger prints the function name. The same applies for logs.
With a macro that defines a function you get a function name that is not
present in the source without pre-processing it. With the callback you
still have the symbol, while the call path may be opaque.
>
> The downside of the code being totally unreadable is way worse than a
> few copied lines.
Well, I was asked in other review to not copy the lines.
Also, the upside is that we can have a syntax-check rule that checks if
qemuSecurity wrapper is used instead of calling bare virSecurity...
I don't think that the macros are a requirement to have a syntax check.
So what about:
int
qemuSecurityRestoreHostdevLabel(virQEMUDriverPtr driver, ...)
{
WRAP(RestoreHostdevLabel); /* macro that wraps
virSecurityManagerRestoreHostdevLabel */
I'd extract the "PROLOGUE" and "EPILOGUE" parts as a function and
then
just call the wrapped function directly. I don't see a point to have a
macro here.
}
This way you can 'vim -t' into it. Although, the syntax-check rule is
going to be much more complex.
Just wrap everything and outlaw it outside of this code then.
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