Yueh-Shun Li <shamrocklee@xxxxxxxxxx> writes: > In section "18) Don't re-invent the kernel macros" in "Linux kernel > coding style": > > Show how reusing macros from shared headers prevents naming collisions > using "stringify", the one of the most widely reinvented macro, as an > example. > > This patch aims to provide a stronger reason to reuse shared macros, > by showing the risk of improvised macro variants. > > Signed-off-by: Yueh-Shun Li <shamrocklee@xxxxxxxxxx> > --- > Documentation/process/coding-style.rst | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst > index 2504cb00a961..1e79aba4b346 100644 > --- a/Documentation/process/coding-style.rst > +++ b/Documentation/process/coding-style.rst > @@ -1070,6 +1070,28 @@ Similarly, if you need to calculate the size of some structure member, use > There are also ``min()`` and ``max()`` macros in ``include/linux/minmax.h`` > that do strict type checking if you need them. > > +Using existing macros provided by the shared headers also prevents naming > +collisions. For example, if one developer define in ``foo.h`` > + > +.. code-block:: c > + > + #define __stringify(x) __stringify_1(x) > + #define __stringify_1(x) #x > + > +and another define in ``bar.h`` > + > +.. code-block:: c > + > + #define stringify(x) __stringify(x) > + #define __stringify(x) #x > + > +When both headers are ``#include``-d into the same file, the facilities provided > +by ``foo.h`` might be broken by ``bar.h``. > + > +If both ``foo.h`` and ``bar.h`` use the macro ``__stringify()`` provided by > +``include/linux/stringify.h``, they wouldn't have stepped onto each other's > +toes. > + So everything we add to our documentation has a cost in terms of reader attention. We ask people to read through a lot of material now, and should only increase that ask for good reason. With that context, I have to wonder whether we really need to tell our readers, who are supposed to be capable developers, that reuse can help to avoid name collisions? Thanks, jon
