realpath.c: include limits.h and use sysconf(_SC_SYMLOOP_MAX)

This is more portable and eliminates the need to check for SYMLOOP_MAX
(and provide it if missing) in configure.  Also quiet some -Wconversion
warnings.

config.h.in

@@ -213,10 +213,6 @@
    don't. */
 #undef HAVE_DECL_SSIZE_MAX
 
-/* Define to 1 if you have the declaration of 'SYMLOOP_MAX', and to 0 if you
-   don't. */
-#undef HAVE_DECL_SYMLOOP_MAX
-
 /* Define to 1 if you have the declaration of 'sys_sigabbrev', and to 0 if you
    don't. */
 #undef HAVE_DECL_SYS_SIGABBREV
@@ -253,10 +249,6 @@
    you don't. */
 #undef HAVE_DECL__POSIX_PATH_MAX
 
-/* Define to 1 if you have the declaration of '_POSIX_SYMLOOP_MAX', and to 0
-   if you don't. */
-#undef HAVE_DECL__POSIX_SYMLOOP_MAX
-
 /* Define to 1 if you have the declaration of '_sys_siglist', and to 0 if you
    don't. */
 #undef HAVE_DECL__SYS_SIGLIST

configure

@@ -28460,19 +28460,6 @@ else case e in #(
 esac
 fi
 printf "%s\n" "#define HAVE_DECL_SSIZE_MAX $ac_have_decl" >>confdefs.h
-ac_fn_check_decl "$LINENO" "SYMLOOP_MAX" "ac_cv_have_decl_SYMLOOP_MAX" "
-#include <sys/types.h>
-#include <limits.h>
-
-" "$ac_c_undeclared_builtin_options" "CFLAGS"
-if test "x$ac_cv_have_decl_SYMLOOP_MAX" = xyes
-then :
-  ac_have_decl=1
-else case e in #(
-  e) ac_have_decl=0 ;;
-esac
-fi
-printf "%s\n" "#define HAVE_DECL_SYMLOOP_MAX $ac_have_decl" >>confdefs.h
 
 ac_fn_check_decl "$LINENO" "SIZE_MAX" "ac_cv_have_decl_SIZE_MAX" "
 #include <sys/types.h>
@@ -28587,25 +28574,6 @@ fi
 printf "%s\n" "#define HAVE_DECL__POSIX_PATH_MAX $ac_have_decl" >>confdefs.h
 
 
-fi
-if test "$ac_cv_have_decl_SYMLOOP_MAX" != "yes"
-then :
-
-    ac_fn_check_decl "$LINENO" "_POSIX_SYMLOOP_MAX" "ac_cv_have_decl__POSIX_SYMLOOP_MAX" "
-#include <sys/types.h>
-#include <limits.h>
-
-" "$ac_c_undeclared_builtin_options" "CFLAGS"
-if test "x$ac_cv_have_decl__POSIX_SYMLOOP_MAX" = xyes
-then :
-  ac_have_decl=1
-else case e in #(
-  e) ac_have_decl=0 ;;
-esac
-fi
-printf "%s\n" "#define HAVE_DECL__POSIX_SYMLOOP_MAX $ac_have_decl" >>confdefs.h
-
-
 fi
 
 

configure.ac

@@ -3323,7 +3323,7 @@ AC_INCLUDES_DEFAULT
 dnl
 dnl Check for incomplete limits.h and missing SIZE_MAX.
 dnl
-AC_CHECK_DECLS([LLONG_MAX, LLONG_MIN, ULLONG_MAX, PATH_MAX, SSIZE_MAX, SYMLOOP_MAX], [], [], [
+AC_CHECK_DECLS([LLONG_MAX, LLONG_MIN, ULLONG_MAX, PATH_MAX, SSIZE_MAX], [], [], [
 #include <sys/types.h>
 #include <limits.h>
 ])
@@ -3369,12 +3369,6 @@ AS_IF([test "$ac_cv_have_decl_PATH_MAX" != "yes"], [
 #include <limits.h>
     ]])
 ])
-AS_IF([test "$ac_cv_have_decl_SYMLOOP_MAX" != "yes"], [
-    AC_CHECK_DECLS([_POSIX_SYMLOOP_MAX], [], [], [[
-#include <sys/types.h>
-#include <limits.h>
-    ]])
-])
 
 dnl
 dnl Check for strsignal() or sys_siglist

include/sudo_compat.h

@@ -103,14 +103,6 @@
 # endif
 #endif
 
-#if defined(HAVE_DECL_SYMLOOP_MAX) && !HAVE_DECL_SYMLOOP_MAX
-# if defined(HAVE_DECL__POSIX_SYMLOOP_MAX) && HAVE_DECL__POSIX_SYMLOOP_MAX
-#  define SYMLOOP_MAX		_POSIX_SYMLOOP_MAX
-# else
-#  define SYMLOOP_MAX		8
-# endif
-#endif
-
 /* ACCESSPERMS and ALLPERMS are handy BSDisms. */
 #ifndef ACCESSPERMS
 # define ACCESSPERMS	00777

lib/util/realpath.c

@@ -40,6 +40,7 @@
 #include <sys/stat.h>
 
 #include <errno.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -58,6 +59,7 @@ sudo_realpath(const char *path, char *resolved)
 	int idx = 0, nlnk = 0;
 	const char *q;
 	char *p, wbuf[2][PATH_MAX], *fres = NULL;
+	static long symloop_max;
 	size_t len;
 	ssize_t n;
 
@@ -66,6 +68,11 @@ sudo_realpath(const char *path, char *resolved)
 		return NULL;
 	}
 
+	if (symloop_max == 0) {
+	    if ((symloop_max = sysconf(_SC_SYMLOOP_MAX)) <= 0)
+		symloop_max = 8;	/* POSIX */
+	}
+
 	if (resolved == NULL) {
 		fres = resolved = malloc(PATH_MAX);
 		if (resolved == NULL)
@@ -145,7 +152,7 @@ loop:
 		goto out;
 	}
 	p[0] = '/';
-	memcpy(&p[1], path, q - path);
+	memcpy(&p[1], path, (size_t)(q - path));
 	p[1 + q - path] = '\0';
 
 	/*
@@ -156,7 +163,7 @@ loop:
 		goto out;
 
 	if (S_ISLNK(sb.st_mode)) {
-		if (nlnk++ >= SYMLOOP_MAX) {
+		if (nlnk++ >= symloop_max) {
 			errno = ELOOP;
 			goto out;
 		}
@@ -169,7 +176,7 @@ loop:
 		}
 
 		/* Append unresolved path to link target and switch to it. */
-		if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
+		if ((size_t)n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
 			errno = ENAMETOOLONG;
 			goto out;
 		}