Re: Bug in macro LOG_MAKEPRI in syslog.h

[Rich Felker <dalias@libc.org>]

On Tue, Oct 06, 2015 at 09:06:49PM +0200, Pepe Aracil wrote:
> Hi all.
> 
> 
> Now the macro is defined as:
> #define LOG_MAKEPRI(f, p) (((f)<<3) | (p))
> And must be:
> #define LOG_MAKEPRI(f, p) ((f) | (p))
> 
> The next example posts wrong facility (LOG_LOCAL1) because LOG_LOCAL1 is
> already rotated ( #define LOG_LOCAL1   (17<<3) ).
> 
> syslog (LOG_MAKEPRI(LOG_LOCAL1, LOG_ERROR),
>         "Unable to make network connection to %s.  Error=%m", host);

Upon further investigation and discussion, it looks like making this
change is the right thing to do. For example:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=729666

I kind of wonder if it would be better to do something like:

#define LOG_MAKEPRI(f, p) (((f)&-8) | (p))

in case programs expecting the old definition use the result of
LOG_FAC. On the other hand this is all cruft, and LOG_FAC is probably
wrong too (anyone have a BSD definition to compare against?) so it
might make sense to just start out with a minimal change.

Best would be to get programs to stop using these bogus and
problematic macros...

Rich