Re: [dpdk-dev] [PATCH v3 0/4] introduce global debug flag

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 14 Jul 2020 00:39:43 +0200
Lukasz Wojciechowski <l.wojciechow@partner.samsung.com> wrote:

> W dniu 11.07.2020 o 17:11, Thomas Monjalon pisze:
> > 09/07/2020 15:48, Lukasz Wojciechowski:  
> >> This set of patches introduces a global rte_debug flag for dpdk.
> >> This will allow easy switch to debug build configuration using a single
> >> flag. In the debug mode a RTE_DEBUG macro is defined to 1
> >> and for every enabled to be built library a RTE_DEBUG_{library name}
> >> and for every enabled to be built driver
> >> a RTE_DEBUG_{driver_class}_{driver_name} is also defined.
> >> These macros can be used to place a debug code
> >> inside #ifdef #endif clauses.
> >>
> >> The following requirements were discussed on the mailing list:
> >> 1) The global debug flag is required to enable all the sanity checks
> >> and validations that are normally not used due to performance reasons
> >>
> >> 2) The best option would be to have a single flag - not to introduce
> >> too many build options
> >>
> >> 3) This option should be separated from meson "debug" option
> >> (used for build with symbols) and can be called "rte_debug"
> >>
> >> 4) The currently existing DEBUG macros should not be replaced with
> >> a RTE_DEBUG macro. This would allow to still enable them using
> >> CFLAGS="-D..." to test a single module (library, driver).  
> > Please can we clarify this point?
> > You mean not replacing driver macros with the global RTE_DEBUG?
> > But we agree (next point) to replace existing macros?  
> Yes, I'll try.
> 
> This point was added after discussion about using a single RTE_DEBUG 
> flag for all debugs.
> I think we all agreed that it will be better to keep separate flags for 
> separate libraries or drivers instead of using only one RTE_DEBUG flag 
> for all debugs.
> e.g. in current version of patches there is a flag RTE_DEBUG_MBUF for 
> debugs related to librte_mbuf.
> This allows to enable only some debugs at compile time passing them to 
> CFLAGS.

Has anyone investigated doing static branches in userspace?
It might mean doing self-modifying code.
That would allow always keeping/compiling in the debug code but at zero runtime cost.