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fix: empty stat-family paths #882

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Merged
alexcrichton merged 1 commit into from
Oct 1, 2026
Merged

fix: empty stat-family paths #882

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1 change: 1 addition & 0 deletions expected/wasm32-wasip1-threads/predefined-macros.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@
#define ARG_MAX 131072
#define ARMAG "!<arch>\n"
#define AT_EACCESS (0x0)
#define AT_EMPTY_PATH (0x8)
#define AT_FDCWD (-2)
#define AT_REMOVEDIR (0x4)
#define AT_SYMLINK_FOLLOW (0x2)
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1 change: 1 addition & 0 deletions expected/wasm32-wasip1/predefined-macros.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@
#define ARG_MAX 131072
#define ARMAG "!<arch>\n"
#define AT_EACCESS (0x0)
#define AT_EMPTY_PATH (0x8)
#define AT_FDCWD (-2)
#define AT_REMOVEDIR (0x4)
#define AT_SYMLINK_FOLLOW (0x2)
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1 change: 1 addition & 0 deletions expected/wasm32-wasip2/predefined-macros.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
#define ARG_MAX 131072
#define ARMAG "!<arch>\n"
#define AT_EACCESS (0x0)
#define AT_EMPTY_PATH (0x8)
#define AT_FDCWD (-2)
#define AT_REMOVEDIR (0x4)
#define AT_SYMLINK_FOLLOW (0x2)
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1 change: 1 addition & 0 deletions expected/wasm32-wasip3-coop/predefined-macros.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
#define ARG_MAX 131072
#define ARMAG "!<arch>\n"
#define AT_EACCESS (0x0)
#define AT_EMPTY_PATH (0x8)
#define AT_FDCWD (-2)
#define AT_REMOVEDIR (0x4)
#define AT_SYMLINK_FOLLOW (0x2)
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1 change: 1 addition & 0 deletions expected/wasm32-wasip3/predefined-macros.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
#define ARG_MAX 131072
#define ARMAG "!<arch>\n"
#define AT_EACCESS (0x0)
#define AT_EMPTY_PATH (0x8)
#define AT_FDCWD (-2)
#define AT_REMOVEDIR (0x4)
#define AT_SYMLINK_FOLLOW (0x2)
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9 changes: 9 additions & 0 deletions libc-bottom-half/cloudlibc/src/libc/sys/stat/fstatat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,15 @@

int __wasilibc_nocwd_fstatat(int fd, const char *restrict path, struct stat *restrict buf,
int flag) {
if (path[0] == '\0') {

@alexcrichton alexcrichton Sep 30, 2026

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Should this also check flag for AT_EMPTY_PATH and skip this check in that case?

@eduardomourar eduardomourar Sep 30, 2026

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I agree with you it should be taken into account. I was looking into POSIX.1-2017 documentation, which does not reference the flag, so I will update the description pointing to POSIX.1-2024 docs.

// With AT_EMPTY_PATH an empty path refers to fd itself; otherwise the
// WASI path-relative stat calls cannot resolve it, so reject as ENOENT.
if (flag & AT_EMPTY_PATH)
return fstat(fd, buf);
errno = ENOENT;
return -1;
}

#if defined(__wasip1__)
__wasi_lookupflags_t lookup_flags = 0;
if ((flag & AT_SYMLINK_NOFOLLOW) == 0)
Expand Down
1 change: 1 addition & 0 deletions libc-bottom-half/headers/public/__header_fcntl.h
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Expand Up @@ -63,6 +63,7 @@
#define AT_SYMLINK_NOFOLLOW (0x1)
#define AT_SYMLINK_FOLLOW (0x2)
#define AT_REMOVEDIR (0x4)
#define AT_EMPTY_PATH (0x8)

#define AT_FDCWD (-2)

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15 changes: 15 additions & 0 deletions libc-bottom-half/sources/posix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,11 @@ ssize_t readlink(const char *restrict path, char *restrict buf,
}

int stat(const char *restrict path, struct stat *restrict buf) {
if (path[0] == '\0') {
errno = ENOENT;
return -1;
}

char *relative_path;
int dirfd = find_relpath(path, &relative_path);

Expand All @@ -106,6 +111,11 @@ int stat(const char *restrict path, struct stat *restrict buf) {
}

int lstat(const char *restrict path, struct stat *restrict buf) {
if (path[0] == '\0') {
errno = ENOENT;
return -1;
}

char *relative_path;
int dirfd = find_relpath(path, &relative_path);

Expand Down Expand Up @@ -387,6 +397,11 @@ int __wasilibc_utimens(const char *path, const struct timespec times[2],
// Like `stat`, but with `fstatat`'s flags argument.
int __wasilibc_stat(const char *__restrict path, struct stat *__restrict st,
int flags) {
if (path[0] == '\0') {
errno = ENOENT;
return -1;
}

char *relative_path;
int dirfd = find_relpath(path, &relative_path);

Expand Down
15 changes: 15 additions & 0 deletions test/src/stat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

#include "test.h"
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
Expand All @@ -27,6 +28,20 @@ int main(void) {
FILE *f;
time_t t;

TEST(stat("", &st) == -1 && errno == ENOENT, "errno = %s\n", strerror(errno));
TEST(lstat("", &st) == -1 && errno == ENOENT, "errno = %s\n",
strerror(errno));
int dirfd = open(".", O_RDONLY);
if (TEST(dirfd >= 0, "errno = %s\n", strerror(errno))) {
TEST(fstatat(dirfd, "", &st, 0) == -1 && errno == ENOENT, "errno = %s\n",
strerror(errno));
if (TEST(fstatat(dirfd, "", &st, AT_EMPTY_PATH) == 0, "errno = %s\n",
strerror(errno))) {
TEST(S_ISDIR(st.st_mode), "\n");
}
close(dirfd);
}

if (TEST(stat(".", &st) == 0, "errno = %s\n", strerror(errno))) {
TEST(S_ISDIR(st.st_mode), "\n");
TEST(st.st_nlink > 0, "%ju\n", (uintmax_t)st.st_nlink);
Expand Down
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