Re: [dpdk-dev] [PATCH v2] cmdline: rework as a wrapper to libedit

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Jun 26, 2018 at 03:21:21PM +0200, Olivier Matz wrote:
> Hi Adrien,
> 
> Better late than never, please find below some comments
> about your patch.
> 
> On Thu, Apr 19, 2018 at 05:13:53PM +0200, Adrien Mazarguil wrote:
> > Disclaimer: this patch must not be confused with the CLI library [1]
> > (work in progress) that will eventually supersede librte_cmdline itself
> > with a different API.
> > 
> > Rather, it modifies librte_cmdline to delegate all the heavy lifting
> > (terminal and history handling), strips unused features and re-implements
> > what remains of its public API as a wrapper to the editline library (also
> > known as libedit) [2], a well-known, BSD-licensed and widely available
> > library used by many projects which does everything needed and more [3].
> > 
> > This approach was chosen because converting librte_cmdline as a wrapper to
> > a more capable library was easier and faster than addressing its
> > shortcomings and results in much less code to maintain in DPDK.
> > 
> > It also provides a drop-in solution for applications that rely on
> > librte_cmdline. They benefit from greatly improved command line handling
> > without a meaningful impact on their code base.
> > 
> > The main motivation behind this patch is testpmd's flow (rte_flow) command,
> > which requires support for dynamic tokens and very long lines that must be
> > broken down when displayed. This is not supported by librte_cmdline's
> > limited terminal handling capabilities, resulting in a rather frustrating
> > user experience.
> > 
> > It had to be addressed given the importance of testpmd as one of the
> > primary tool used by PMD developers.
> > 
> > This rework results in the following changes:
> > 
> > - Removed circular buffer management interface for command history
> >   (cmdline_cirbuf.c), command history being handled by libedit.
> > - Removed raw command-line interpreter (cmdline_rdline.c).
> > - Removed raw terminal handler (cmdline_vt100.c).
> > - Removed all test/example code for the above.
> > - Re-implemented high level interactive and non-interactive command-line
> >   handlers (cmdline.c and cmdline_socket.c) on top of libedit using its
> >   native interface, not its readline compatibility layer.
> > - Made struct cmdline opaque so that applications relying on librte_cmdline
> >   do not need to include any libedit headers.
> > - Applications do not need to include cmdline_rdline.h anymore.
> > - Terminal resizing is now automatically handled.
> > - New external dependency for applications relying on librte_cmdline.
> > - Major version bump due to the ABI impact of these changes.
> > 
> > [1] http://dpdk.org/browse/draft/dpdk-draft-cli/
> > [2] http://thrysoee.dk/editline/
> > [3] http://netbsd.gw.com/cgi-bin/man-cgi?editline++NetBSD-current
> > 
> > Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> > Cc: Olivier Matz <olivier.matz@6wind.com>
> > Cc: Keith Wiles <keith.wiles@intel.com>
> > Cc: Jingjing Wu <jingjing.wu@intel.com>
> > Cc: Thomas Monjalon <thomas@monjalon.net>
> > Cc: Ferruh Yigit <ferruh.yigit@intel.com>
> > Cc: Jim Thompson <jim@netgate.com>
> > Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> > 
> > --
> > 
> > v2 changes:
> > 
> > - Replaced an instance of snprintf() with rte_strlcpy() [5].
> > - Rebased patch.
> > 
> > [5] http://dpdk.org/ml/archives/dev/2018-April/097721.html
> > 
> > v1 changes:
> > 
> > No fundamental change since the original RFC [4], except it's been rebased
> > several times and Meson build support was added in the meantime. Commit log
> > was also shortened a bit.
> > 
> > I'm re-sending this because I think it's useful, at least to me (duh). As
> > the maintainer of rte_flow, I spend most of my time typing flow commands in
> > testpmd and libedit makes that a pleasant experience.
> > 
> > Try it out! And don't hesitate to send your acked-by line to get this in
> > time for 18.05 :)
> > 
> > [4] http://dpdk.org/ml/archives/dev/2017-November/081605.html
> 
> Re-saying what I said the first time: I think this is a very good
> improvement, removing lots of dpdk code that is better implemented in
> well-known libraries.
> 
> 
> The compilation with shared libraries fail. Please try for instance:
> ./devtools/test-build.sh -j4 x86_64-native-linuxapp-clang+shared+debug
> 
> I suggest to add in lib/librte_cmdline/Makefile:
> 
>   LDLIBS += $(shell pkg-config --libs libedit)
> 
> 
> I also think something should be added in
> /doc/guides/linux_gsg/sys_reqs.rst to highlight the new build
> dependency.
> 
> 
> I noticed a bad behavior change (in addition to many good ones):
> ctrl-c now quits the application, and this was not the case before.
> I often use ctrl-c to delete the line I'm currently editing. Please
> see at the end a proposition to restore this feature.
> 

I 100% disagree, please set things up that "ctrl-c" quits the application.

Having our DPDK testpmd and auto-test apps fail to close on ctrl-c is just
awful from a usability perspective IMHO! If there is ever a problem with
the app and you need to kill it quickly, e.g. you want to stop one of those
long-running autotests, the lack of ctrl-c is a pain.

For me, the only valid use-case for a command-line app to catch the signal
from ctrl-c is to allow the app to do some cleanup before it quits.

/Bruce