On Fri, 2017-03-31 at 10:34 -0700, Steve deRosier wrote:

On Fri, Mar 31, 2017 at 10:23 AM, Joe Perches [off-list ref] wrote:

quoted

On Fri, 2017-03-31 at 10:19 -0700, Steve deRosier wrote:

quoted

On Thu, Mar 30, 2017 at 3:57 PM, Joe Perches [off-list ref] wrote:

quoted

Fix fallout too.

[]

quoted

My only question is why bother doing a format check on something
that's going to be compiled out anyway?

To avoid introducing defects when writing new code
and not using the debugging code path.

Fair enough. And I totally agree with the defensive programming here
in that case and feel it's worth the tradeoff (if indeed there really
is any cost, I'm unsure what gcc actually does in this instance).

For sake of discussion though - shouldn't anything not using the debug
code path in this case always be of the form that compiles out? ie
would be empty functions intended here just to make compilation work
and the code that depends on it simpler? Thus, there really should
never be a risk of introducing said defects. If any "real" code were
put in that else clause, that'd be a big red-flag in the review of
said hypothetical patch.

Generically, all debugging forms should strive to avoid side-effects.

For instance, look at no_printk/pr_debug in the #ifndef DEBUG paths.

It uses if (0) to avoid compilation of arguments that might be
function calls or volatile accesses and so might have side-effects
altogether.

include/linux/printk.h-/*
include/linux/printk.h- * Dummy printk for disabled debugging statements to use whilst maintaining
include/linux/printk.h- * gcc's format checking.
include/linux/printk.h- */
include/linux/printk.h:#define no_printk(fmt, ...)                              \
include/linux/printk.h-({                                                       \
include/linux/printk.h- do {                                            \
include/linux/printk.h-         if (0)                                  \
include/linux/printk.h-                 printk(fmt, ##__VA_ARGS__);     \
include/linux/printk.h- } while (0);                                    \
include/linux/printk.h- 0;                                              \
include/linux/printk.h-})
i