Use dynamic maximum configuration values when necessary (#370)

This commit fixes an issue with how ksh was obtaining the value of
NGROUPS_MAX. On some systems this setting can be changed (e.g., on
illumos adding 'set ngroups_max=32' to /etc/system then rebooting
changes NGROUPS_MAX from 16 to 32). Ksh was using NGROUPS_MAX with
the assumption it's a static value, which could cause issues on
systems where it isn't static. This bugfix is inspired by the one
from <b1362c3a5>, although it
has been expanded a bit to account for OPEN_MAX as well.

src/cmd/ksh93/sh/init.c, src/lib/libcmd/fds.c:
- Rename the getconf() macro to astconf_long() and move it to ast.h
  to prevent redundancy. Other sections of the code have been
  modified to use this macro for astconf() to account for
  dynamic settings.
- An equivalent macro for unsigned long values (astconf_ulong) has
  been added.
- Prefer sysconf(3) where available. It has better performance as it
  returns a numeric value directly instead of via string
  conversion.
- The astconf_long and astconf_ulong macros have been documented in
  the ast(3) man page.

src/cmd/ksh93/bltins/test.c

@@ -666,7 +666,7 @@ skip:
 				if((maxgroups=getgroups(0,(gid_t*)0)) <= 0)
 				{
 					/* pre-POSIX system */
-					maxgroups=NGROUPS_MAX;
+					maxgroups = (int)astconf_long(CONF_NGROUPS_MAX);
 				}
 			}
 			groups = (gid_t*)stakalloc((maxgroups+1)*sizeof(gid_t));
@@ -680,7 +680,7 @@ skip:
 				}
 			}
 		}
-#   endif /* _lib_getgroups */
+#endif /* _lib_getgroups */
 		if(statb.st_mode & mode)
 			return(0);
 	}

src/cmd/ksh93/features/externs

@@ -46,7 +46,7 @@ tst	note{ determining extra bytes per argument for arguments list }end output{
 			for(i=0; environ[i]; i++)
 				envlen += strlen(environ[i]) + 1 + extra_bytes;
 			envlen += 1 + extra_bytes;	/* final null element */
-			argmax = strtoimax(astconf("ARG_MAX",NiL,NiL),NiL,0) - envlen;
+			argmax = (int)astconf_long(CONF_ARG_MAX) - envlen;
 			if (argmax < 2048)
 			{
 				error(ERROR_ERROR|2, "argmax too small");

src/cmd/ksh93/sh/init.c

@@ -144,9 +144,6 @@ char e_version[]	= "\n@(#)$Id: Version "
     extern char	**environ;
 #endif
 
-#undef	getconf
-#define getconf(x)	strtol(astconf(x,NiL,NiL),NiL,0)
-
 struct seconds
 {
 	Namfun_t	hdr;
@@ -1223,9 +1220,9 @@ Shell_t *sh_init(register int argc,register char *argv[], Shinit_f userinit)
 		shgd->euserid=geteuid();
 		shgd->groupid=getgid();
 		shgd->egroupid=getegid();
-		shgd->lim.clk_tck = getconf("CLK_TCK");
-		shgd->lim.arg_max = getconf("ARG_MAX");
-		shgd->lim.child_max = getconf("CHILD_MAX");
+		shgd->lim.arg_max = astconf_long(CONF_ARG_MAX);
+		shgd->lim.child_max = (int)astconf_long(CONF_CHILD_MAX);
+		shgd->lim.clk_tck = (int)astconf_long(CONF_CLK_TCK);
 		if(shgd->lim.arg_max <=0)
 			shgd->lim.arg_max = ARG_MAX;
 		if(shgd->lim.child_max <=0)

src/cmd/ksh93/sh/io.c

@@ -403,7 +403,7 @@ int  sh_iovalidfd(Shell_t *shp, int fd)
 		return(0);
 	if(fd < shp->gd->lim.open_max)
 		return(1);
-	max = strtol(astconf("OPEN_MAX",NiL,NiL),NiL,0);
+	max = (int)astconf_long(CONF_OPEN_MAX);
 	if(fd >= max)
 	{
 		errno = EBADF;

src/cmd/ksh93/sh/suid_exec.c

@@ -329,7 +329,7 @@ int eaccess(register const char *name, register int mode)
 				if((maxgroups=getgroups(0,groups)) < 0)
 				{
 					/* pre-POSIX system */
-					maxgroups=NGROUPS_MAX;
+					maxgroups = (int)astconf_long(CONF_NGROUPS_MAX);
 				}
 			}
 			groups = (gid_t*)malloc((maxgroups+1)*sizeof(gid_t));