Date: Wed, 17 Jul 2013 15:19:49 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Subject: Re: time code progress * Jens Gustedt <jens.gustedt@...ia.fr> [2013-07-17 14:09:38 +0200]: > Am Mittwoch, den 17.07.2013, 13:39 +0200 schrieb Szabolcs Nagy: > > (i think it did not like the syscall arg counting in case of 0 args in > > #define __SYSCALL_NARGS_X(a,b,c,d,e,f,g,h,n,...) n > > #define __SYSCALL_NARGS(...) __SYSCALL_NARGS_X(__VA_ARGS__,7,6,5,4,3,2,1,0) > > ) > > yes, this is in fact not suitable to test for 0 args. For the > preprocessor 0 args basically doesn't exist, there is always one > argument, but which is empty. > note that the problem is not that __VA_ARGS__ is empty (it's not, contrary to what i might implied), but that if n becomes 0 (== __VA_ARGS__ expands to one argument), then there is no more arguments in the __SYSCALL_NARGS_X call to substitute for '...', so a simple fix would be #define __SYSCALL_NARGS(...) __SYSCALL_NARGS_X(__VA_ARGS__,7,6,5,4,3,2,1,0, tralala) but i'm not sure if this should be fixed (this is internal code and i think there are no 0 argument syscalls) i just wanted to record how i found the close without fd issue (which shows that some kind of type checking for syscall arguments would help libc hacking.. but that's non-trivial to do)
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