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posix: implement missing directory functions #433

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posix: implement missing directory functions #433

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78c1c32
posix: implement missing directory functions
R4ken Aug 13, 2025
ca26bd4
posix: introduce NULL checks in *dir routines
oI0ck Nov 26, 2025
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5 changes: 5 additions & 0 deletions include/dirent.h
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,11 @@ extern struct dirent *readdir(DIR *s);

extern DIR *opendir(const char *dirname);

extern DIR *fdopendir(int fd);

extern void seekdir(DIR *dirp, long loc);

extern long telldir(DIR *dirp);

extern void rewinddir(DIR *dirp);

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64 changes: 64 additions & 0 deletions unistd/dir.c
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Expand Up @@ -26,6 +26,7 @@
#include <sys/stat.h>
#include <sys/file.h>
#include <posix/utils.h>
#include <fcntl.h>


static struct {
Expand Down Expand Up @@ -440,6 +441,69 @@ DIR *opendir(const char *dirname)
}


DIR *fdopendir(int fd)
{
DIR *s;
struct stat statbuf;
int fd_flags;

fd_flags = fcntl(fd, F_GETFL);
if (fd_flags < 0) {
return NULL;
}
if ((fd_flags & O_RDONLY) == 0) {
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@Darchiv Darchiv Sep 30, 2025

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What if O_RDWR is set, so O_RDONLY is not? I think a file descriptor open for reading can be as well open for writing, as long as it is still readable

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@R4ken R4ken Sep 30, 2025 •
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open from libphoenix sets EISDIR on errno while opening directory with either O_WRONLY or O_RDWR flag.
Thus opening directory with O_RDWR is not possible

Fragment of open function from libphoenix

if (oflag & (O_WRONLY | O_RDWR)) {
  if ((err = stat(filename, &st)) < 0) {
	  if (errno != ENOENT)
		  return err;
  }
  else if (S_ISDIR(st.st_mode)) {
	  return SET_ERRNO(-EISDIR);
  }
}

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@oI0ck oI0ck Nov 26, 2025

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This behaviour seems common, I can replicate it on both Linux and one of the BSD's, I think we can keep it like that for the sake of compatibility.

errno = EBADF;
return NULL; /* EBADF */
}

if (fstat(fd, &statbuf) < 0) {
return NULL;
}

msg_t msg = {
.type = mtGetAttr,
.oid = { .port = statbuf.st_dev, .id = statbuf.st_ino },
.i.attr.type = atType,
};

if ((msgSend(statbuf.st_dev, &msg) < 0) || (msg.o.err < 0)) {
errno = EIO;
return NULL; /* EIO */
}

if (msg.o.attr.val != otDir) {
errno = ENOTDIR;
return NULL; /* ENOTDIR */
}

if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0) {
return NULL;
}

s = calloc(1, sizeof(DIR));
if (s == NULL) {
errno = ENOMEM;
return NULL;
}
s->oid = msg.oid;
s->dirent = NULL;

return s;
}


void seekdir(DIR *dirp, long loc)
{
dirp->pos = loc;
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high

The function should handle the case where dirp is NULL to prevent a segmentation fault. Dereferencing a NULL pointer is undefined behavior.

	if (dirp != NULL)
		dirp->pos = loc;

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@R4ken R4ken Sep 25, 2025

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Other libphoenix functions don't validate whether dirp is non NULL pointer

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@oI0ck oI0ck Nov 26, 2025

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Yes, you are right, although I think that this might be a good opportunity to introduce those checks here.
Linux's behaviour in these calls is not unreasonable and helping the programmer by making this deterministic is IMO good

}


long telldir(DIR *dirp)
{
return dirp->pos;
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high

The function should handle the case where dirp is NULL. According to the POSIX standard, if dirp does not refer to a valid directory stream, telldir() should return -1 and set errno to EBADF.

	if (dirp == NULL) {
		errno = EBADF;
		return -1;
	}
	return dirp->pos;

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@R4ken R4ken Sep 17, 2025

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No, this behavior exists in Linux, POSIX does not specify it

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@oI0ck oI0ck Nov 26, 2025

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As above

}


void rewinddir(DIR *dirp)
{
dirp->pos = 0;
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