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#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"
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;
}
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