On Tue, Dec 14, 2021 at 01:58:03AM +0300, Dmitry Kozlyuk wrote: > 2021-12-10 14:53 (UTC+0000), Bruce Richardson: > [...] > > Acked-by: Dmitry Kozlyuk <dmitry.kozl...@gmail.com> > with one typo below and some considerations for the future in the bottom. > > > +Defines to Avoid Conditional Compilation > > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > + > > +In many cases in DPDK, one wants to optionally compile code based on the > > target platform, > > +or runtime environment. > > "Compile" -> "run", that's the point to use conditionals instead of macros. > > > +While this can be done using the conditional compilation directives, > > +e.g. ``#ifdef RTE_EXEC_ENV_LINUX``, present in DPDK for many releases, > > +this can also be done in many cases using regular ``if`` statements and > > the following defines: > > > + > > +* ``RTE_ENV_FREEBSD``, ``RTE_ENV_LINUX``, ``RTE_ENV_WINDOWS`` - these > > define ids for each operating system environment. > > +* ``RTE_EXEC_ENV`` - this defines the id of the current environment, i.e. > > one of the items in list above. > > +* ``RTE_EXEC_ENV_IS_FREEBSD``, ``RTE_EXEC_ENV_IS_LINUX``, > > ``RTE_EXEC_ENV_IS_WINDOWS`` - 0/1 values indicating if the current > > environment is that specified, > > + shortcuts for checking e.g. ``RTE_EXEC_ENV == RTE_ENV_WINDOWS`` > [...] > > I wonder whether #if RTE_EXEC_ENV_IS_xxx > should be preferred over #ifdef RTE_EXEC_ENV_xxx, > so that all checks use the same symbol > (and then remove old macros one day). > > Since C conditionals are preferred over #ifdef, > I suggest to give pointers when to use one or another mechanism: > > If a code fragment can compile on all platforms, > but cannot run on some due to lack of support, > branch on constants. > > If a code fragment cannot compile on all platforms > (e.g. use of OS-specific headers or macros), > but constitutes only a small fraction of the file, > use conditional compilation. > > If a group of functions implement an interface > in an OS- or platform-specific way, > create a file for each of the supported environments > and plug an appropriate file from ``meson.build``.
Good suggestions. I rework into a v2 when I get the chance. /Bruce
