Re: [dpdk-dev] [PATCH v2] ABI: Add abi checking utility

[Neil Horman <nhorman@tuxdriver.com>]

On Wed, Mar 04, 2015 at 01:54:49PM +0100, Thomas Monjalon wrote:
> Hi Neil,
> 
> I remove parts that I agree and reply to those which deserve more discussion.
> 
> 2015-03-04 06:49, Neil Horman:
> > On Tue, Mar 03, 2015 at 11:18:47PM +0100, Thomas Monjalon wrote:
> > > 2015-02-02 13:18, Neil Horman:
> > > > +# Validate that we have all the arguments we need
> > > > +res=$(validate_args)
> > > > +if [ -n "$res" ]
> > > > +then
> > > > +	echo $res
> > > 
> > > Should be redirected to stderr >&2
> > > 
> > Why? this is eactly what I intended.  All the other messages from log are
> > directed to stdout, so should this be.
> 
> I'm wondering if there's some normal output which could be redirected for
> further processing, and some error output.
> My comment was not only for this log but also for every error message.
> 

No, the report output is in html format and always to a file, so stdout isn't
used for any inline informational reporting.

> > > I guess this is the tool:
> > > 	http://ispras.linuxbase.org/index.php/ABI_compliance_checker
> > 
> > Correct.
> 
> So maybe you should add this URL in the commit log.
> 
sure, fine.

> > > > +log "INFO" "We're going to check and make sure that applications built"
> > > > +log "INFO" "against DPDK DSOs from tag $TAG1 will still run when executed"
> > > > +log "INFO" "against DPDK DSOs built from tag $TAG2."
> > > > +log "INFO" ""
> 
> > > > +if [ ! -d ./.git ]
> > > > +then
> > > > +	log "WARN" "You must be in the root of the dpdk git tree"
> > > > +	log "WARN" "You are in $PWD"
> > > > +	cleanup_and_exit 1
> > > > +fi
> > > 
> > > Why not cd $(dirname $0)/.. instead of returning an error?
> > 
> > Why would that help in finding the base of the git tree.  Theres no guarantee
> > that you are in a subdirectory of a git tree.  I suppose we can try it
> > recursively until we hit /, but it seems just as easy and clear to tell the user
> > whats needed.
> 
> No I'm saying that you could avoid this check by going into the right
> directory from the beginning.
> We know that the root dir is $(dirname $0)/.. because this script is in
> scripts/ directory.
> 
That only helps if you start from the right directory.  If you run this command
from some other location, your solution just breaks.

> > > > +# Make sure we configure SHARED libraries
> > > > +# Also turn off IGB and KNI as those require kernel headers to build
> > > > +sed -i -e"$ a\CONFIG_RTE_BUILD_SHARED_LIB=y" config/defconfig_$TARGET
> > > > +sed -i -e"$ a\CONFIG_RTE_EAL_IGB_UIO=n" config/defconfig_$TARGET
> > > > +sed -i -e"$ a\CONFIG_RTE_LIBRTE_KNI=n" config/defconfig_$TARGET
> > > 
> > > Why not tuning configuration after make config in .config file?
> > > 
> > Because this way we save a reconfig (from a developer viewpoint), you should run
> > make config again after changing configs, and so this way you save doing that.
> 
> No, you run make config once and update .config file. That's the recommended
> way to configure DPDK.
> defconfig files are default configurations and should stay read-only.
They get overwritten when we do the git resets.  Its silly to modify your config
file after you run make config, in the event the make target has to re-read any
modified options and adjust dependent config files accordingly.  I understand
that doesn't happen now, but its common practice for every open source project
in existance.

> 
> > > > +for i in `ls *.so`
> > > 
> > > I think ls is useless.
> > > 
> > Um, I don't?  Not sure what you're getting at here.
> 
> I think "for i in *.so" should work.
> 
Then its irrelevant in my mind.  They both work equally well.


> > > > +	#compare the abi dumps
> > > > +	$ABICHECK -l $LIBNAME -old $ABI_DIR/$OLDNAME -new $ABI_DIR/$NEWNAME
> > > 
> > > Do we need to do a visual check? I didn't try yet.
> > > 
> > Yes, it generates an html report of all the symbols exported in a build and
> > compares them with the alternate version.  That needs manual review.
> 
> OK I think it's important to explain in the commit log.
Ok.

> 
> > > So you compare the ABI dumps.
> > > Do we also need to run an app from TAG2 with libs from TAG1?
> > 
> > I started down that path, but its not really that helpful, as all it will do is
> > refuse to run if there is a symbol missing from a later version.  While that
> > might be helpful, its no where near as through as the full report from the
> > compliance checker.
> > 
> > The bottom line is that real ABI compliance requires a developer to be aware of
> > the changes going into the code and how they affect binary layout. A simple
> > "does it still work" test isn't sufficient.
> 
> I hope we'll be able to integrate this kind of tool in an automated sanity
> check in order to find obvious errors.
> 
> Thanks
>