#include <stdlib.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+#include "syscall.h"
-char *realpath(const char *filename, char *resolved)
+void __procfdname(char *, unsigned);
+
+char *realpath(const char *restrict filename, char *restrict resolved)
{
+ int fd;
+ ssize_t r;
+ struct stat st1, st2;
+ char buf[15+3*sizeof(int)];
+ char tmp[PATH_MAX];
+
+ if (!filename) {
+ errno = EINVAL;
+ return 0;
+ }
+
+ fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC);
+ if (fd < 0) return 0;
+ __procfdname(buf, fd);
+
+ r = readlink(buf, tmp, sizeof tmp - 1);
+ if (r < 0) goto err;
+ tmp[r] = 0;
+
+ fstat(fd, &st1);
+ r = stat(tmp, &st2);
+ if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
+ if (!r) errno = ELOOP;
+ goto err;
+ }
+
+ __syscall(SYS_close, fd);
+ return resolved ? strcpy(resolved, tmp) : strdup(tmp);
+err:
+ __syscall(SYS_close, fd);
return 0;
}