On 25 December 2016 at 20:41, Gert Doering <g...@greenie.muc.de> wrote: > On Sun, Dec 25, 2016 at 08:58:23PM +0800, Antonio Quartulli wrote: >> What is the general rule then? cron2 explained me on IRC that in the past >> some C >> programs would crash when trying to print NULL, but it should not be >> the case anymore (at least on Linux). > > As mentioned occasionally, we run on more than Linux. So this is only > safe if all supported platforms can handle > > printf( "%s\n", NULL ); > > correctly - Solaris, all the BSDs, MacOS, Windows(!), AIX. > > "It works on Linux" is good, but this is a "boolean and" condition - it > needs to work on *all* supported platforms. > > I'm not generally opposed to modernizing the code, but the onus of > recherching whether such a change is safe is on the proposer.
We use -std=c99, and according to C99, passing a NULL to printf() results in undefined behaviour. Excerpt from the C99 standard, section 7.1.4 "Use of library functions": "Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as [...] or a null pointer, [...]) or [...], the behavior is undefined." The section about printf() does not state otherwise. Some, most or all platforms we support might print "(null)", but I don't think it's wise to rely on that. So yes, if the pointer can be NULL, I think we should check for it. In this case, in particular with the (new) wrapper, I think it is simpler to just check for NULL then to figure out if the code can ever be passed a NULL pointer. At least the np() wrappers that are used seem to indicate that it might be possible. -Steffan ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today.http://sdm.link/intel _______________________________________________ Openvpn-devel mailing list Openvpn-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openvpn-devel
