> > Hi, > > I stumbled across the following definitions in <sys/param.h>, which are > defined in Linux, but not in Hurd: > > /* BSD names for some <limits.h> values. */ > > #define NBBY CHAR_BIT > #ifndef NGROUPS > #define NGROUPS NGROUPS_MAX > #endif > #define MAXSYMLINKS 5 > #define CANBSIZ MAX_CANON > #define NCARGS ARG_MAX > #define MAXPATHLEN PATH_MAX > #define NOFILE OPEN_MAX
The current hurd <sys/params.h> does define NBBY, NGROUPS, MAXSYMLINKS, CANBSIZ, and NCARGS. The NCARGS and NGROUPS definitions are fictitious, since there are no actual limits on those things. > Especially the last two are used frequently. No program that uses them unconditionally complies to 1003.1-1996. > Notice that neither PATH_MAX nor OPEN_MAX are defined in Hurd, too. > > Why? Because there are no limits. Aside from runtime memory availability, there is no limit whatsoever on the length of a file name imposed by the system architecture (individual filesystems may have limits, which pathconf reports). The only limit on open file descriptors is the soft resource limit settable with setrlimit(RLIM_NOFILE). A POSIX-compliant program takes absence of these definitions to mean there is no limit determinable at compile-time, and uses sysconf or pathconf as appropriate to ascertain the run-time limits; in most cases, they can return -1 to indicate there is no ascertainable limit. When that is true on the Hurd, that is what it returns. I can dig the standard out and quote chapter and verse if it would help.
