posix: implement missing directory functions #433

R4ken · 2025-09-01T14:42:12Z

Implement missing POSIX functions (fdopendir,seekdir, telldir) working on DIR structs

JIRA: RTOS-1088

Description

Implemented fdopendir,seekdir and telldir functions.

Motivation and Context

Missing POSIX functions useful in porting applications

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)
Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

Already covered by automatic testing.
New test added: (add PR link here).
Tested by hand on: (ia32-generic-qemu, armv7a9-zynq7000-qemu)

Checklist:

My change requires a change to the documentation.
I have updated the documentation accordingly.
I have added tests to cover my changes.
All new and existing linter checks and tests passed.
My changes generate no new compilation warnings for any of the targets.

Special treatment

This PR needs additional PRs to work (list the PRs, preferably in merge-order).
I will merge this PR by myself when appropriate.

gemini-code-assist

Summary of Changes

Hello @R4ken, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces three essential POSIX directory functions: fdopendir, seekdir, and telldir. These additions are crucial for improving the system's compatibility with POSIX standards, thereby simplifying the porting of various applications that rely on these common directory operations. The changes enhance the system's file system interaction capabilities without altering existing functionality.

Highlights

New POSIX Directory Functions: Implemented fdopendir, seekdir, and telldir functions to provide more comprehensive POSIX-compliant directory manipulation capabilities.
Header Updates: Added declarations for the new directory functions in include/dirent.h.
Core Logic Implementation: Provided the full implementation for fdopendir, seekdir, and telldir within unistd/dir.c, including necessary error handling and file descriptor management.

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unistd/dir.c

gemini-code-assist

Code Review

This pull request implements the missing POSIX directory functions fdopendir, seekdir, and telldir. The implementations are a good start, but I've identified a few high-severity issues related to null pointer dereferences and error handling that could lead to crashes or undefined behavior. I've provided detailed comments and code suggestions to address these points, which also include a small efficiency improvement in fdopendir.

unistd/dir.c

gemini-code-assist · 2025-09-01T14:44:19Z

unistd/dir.c

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


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;

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

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

gemini-code-assist · 2025-09-01T14:44:19Z

unistd/dir.c

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


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;

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

github-actions · 2025-09-01T14:56:32Z

Unit Test Results

9 462 tests +185 8 872 ✅ +185 51m 13s ⏱️ - 3m 22s
561 suites + 16 589 💤 ± 0
1 files ± 0 1 ❌ ± 0

For more details on these failures, see this check.

Results for commit ca26bd4. ± Comparison against base commit ebfb737.

♻️ This comment has been updated with latest results.

unistd/dir.c

Darchiv · 2025-09-30T13:12:11Z

unistd/dir.c

+		free(s);
+		return NULL;
+	}
+	if ((fd_flags & O_RDONLY) == 0) {


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

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); } }

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.

unistd/dir.c

Implement missing POSIX functions (fdopendir,seekdir, telldir) working on DIR structs JIRA: RTOS-1088

oI0ck

I'd be good to introduce NULL checks while we are at it.

oI0ck · 2025-11-26T13:29:11Z

unistd/dir.c

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


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

oI0ck · 2025-11-26T13:29:16Z

unistd/dir.c

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


oI0ck · 2025-11-26T13:56:14Z

unistd/dir.c

+		free(s);
+		return NULL;
+	}
+	if ((fd_flags & O_RDONLY) == 0) {


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.

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R4ken marked this pull request as draft September 1, 2025 14:46

R4ken requested a review from jlatusek September 2, 2025 06:48

R4ken force-pushed the jrak/dir branch from f5f2225 to c48cb8e Compare September 2, 2025 07:00

R4ken requested a review from Darchiv September 8, 2025 15:08

R4ken marked this pull request as ready for review September 25, 2025 07:39

R4ken mentioned this pull request Sep 30, 2025

WASM: add webassembly-micro-runtime port phoenix-rtos/phoenix-rtos-ports#120

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posix: implement missing directory functions

78c1c32

Implement missing POSIX functions (fdopendir,seekdir, telldir) working on DIR structs JIRA: RTOS-1088

R4ken force-pushed the jrak/dir branch from aef8a73 to 78c1c32 Compare September 30, 2025 13:49

Darchiv removed the request for review from jlatusek November 26, 2025 13:51

oI0ck requested changes Nov 26, 2025

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posix: introduce NULL checks in *dir routines

ca26bd4

oI0ck requested a review from Darchiv November 26, 2025 14:12

posix: implement missing directory functions #433

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posix: implement missing directory functions #433

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R4ken commented Sep 1, 2025

Description

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Checklist:

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