On Thu, Feb 12 2015, "Rustad, Mark D" <[email protected]> wrote:
> On Feb 11, 2015, at 2:51 PM, Rasmus Villemoes <[email protected]> > wrote: > >> Since these fmt_* variables are just const char*, and not const >> char[], gcc (and smatch) doesn't to type checking of the arguments to >> the printf functions. Since the linker knows perfectly well to merge >> identical string constants, there's no point in having three static >> pointers waste memory and give an extra level of indirection. >> >> This removes over 100 "non-constant format argument" warnings from >> smatch, accounting for about 20% of all such warnings in an >> allmodconfig. >> >> Signed-off-by: Rasmus Villemoes <[email protected]> >> --- >> drivers/net/wireless/iwlegacy/4965-debug.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/net/wireless/iwlegacy/4965-debug.c >> b/drivers/net/wireless/iwlegacy/4965-debug.c >> index e0597bfdddb8..18855325cc1c 100644 >> --- a/drivers/net/wireless/iwlegacy/4965-debug.c >> +++ b/drivers/net/wireless/iwlegacy/4965-debug.c >> @@ -28,10 +28,9 @@ >> #include "common.h" >> #include "4965.h" >> >> -static const char *fmt_value = " %-30s %10u\n"; >> -static const char *fmt_table = " %-30s %10u %10u %10u %10u\n"; >> -static const char *fmt_header = >> - "%-32s current cumulative delta max\n"; > > Why not change these to: > static const char fmt_value[] = " %-30s %10u\n"; > static const char fmt_table[] = " %-30s %10u %10u %10u %10u\n"; > static const char fmt_header[] = > "%-32s current cumulative delta max\n"; > > I think that is better than the macros and avoids the extra pointers that I > agree are useless. Rather weak arguments, but I have three of them :-) (1) If I'm reading some code and spot a non-constant format argument, I sometimes track back to see how e.g. fmt_value is defined. If I then see it's a macro, I immediately think "ok, the compiler is doing type-checking". If it is a const char[], I have to remember that gcc also does it in that case (as opposed to for example const char*const). (2) The names of these variables themselves may end up wasting a few bytes in the image. (3) gcc/the linker doesn't merge identical const char[] arrays across translation units. It also doesn't consider their tails for merging with string literals. So although these specific strings are unlikely to appear elsewhere, a string such as "%10u\n" or "max\n" couldn't be merged with one of the above. Rasmus -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
