Handle AT_SYMLINK_NOFOLLOW in __syscall_faccessat

src/lib/libsyscall.js

@@ -930,14 +930,15 @@ var SyscallsLibrary = {
   __syscall_faccessat: (dirfd, path, amode, flags) => {
     path = SYSCALLS.getStr(path);
 #if ASSERTIONS
-    assert(!flags || flags == {{{ cDefs.AT_EACCESS }}});
+    assert(!(flags & ~({{{ cDefs.AT_EACCESS }}} | {{{ cDefs.AT_SYMLINK_NOFOLLOW }}})));
 #endif
     path = SYSCALLS.calculateAt(dirfd, path);
     if (amode & ~{{{ cDefs.S_IRWXO }}}) {
       // need a valid mode
       return -{{{ cDefs.EINVAL }}};
     }
-    var lookup = FS.lookupPath(path, { follow: true });
+    var nofollow = !!(flags & {{{ cDefs.AT_SYMLINK_NOFOLLOW }}});
+    var lookup = FS.lookupPath(path, { follow: !nofollow });
     var node = lookup.node;
     if (!node) {
       return -{{{ cDefs.ENOENT }}};

test/unistd/access.c

@@ -76,6 +76,29 @@ void test_lchmod() {
 #endif
 }
 
+void test_symlink_nofollow() {
+  FILE* f = fopen("target_file", "w");
+  fclose(f);
+  symlink("target_file", "test_symlink");
+  symlink("dangling_target", "dangling_symlink");
+
+  // With AT_SYMLINK_NOFOLLOW, faccessat checks the symlink itself, not the target
+  printf("F_OK symlink nofollow: %s\n",
+    faccessat(AT_FDCWD, "test_symlink", F_OK, AT_SYMLINK_NOFOLLOW) == 0 ? "OK" : strerror(errno));
+
+  // Dangling symlink should still be found with AT_SYMLINK_NOFOLLOW (symlink exists)
+  printf("F_OK dangling nofollow: %s\n",
+    faccessat(AT_FDCWD, "dangling_symlink", F_OK, AT_SYMLINK_NOFOLLOW) == 0 ? "OK" : strerror(errno));
+
+  // Without AT_SYMLINK_NOFOLLOW, dangling symlink should fail
+  printf("F_OK dangling follow: %s\n",
+    faccessat(AT_FDCWD, "dangling_symlink", F_OK, 0) == 0 ? "OK" : strerror(errno));
+
+  // Combined flags should work
+  printf("F_OK symlink eaccess|nofollow: %s\n",
+    faccessat(AT_FDCWD, "test_symlink", F_OK, AT_EACCESS | AT_SYMLINK_NOFOLLOW) == 0 ? "OK" : strerror(errno));
+}
+
 void test_chmod_errors() {
   EM_ASM(
     var ex;
@@ -119,6 +142,7 @@ int main() {
   test_rename();
   test_fchmod();
   test_lchmod();
+  test_symlink_nofollow();
   test_chmod_errors();
 
   return 0;

test/unistd/access.out

@@ -32,3 +32,7 @@ F_OK('filetorename'): -1
 F_OK('renamedfile'): 0
 F_OK('filetorename'): -1
 F_OK('renamedfile'): 0
+F_OK symlink nofollow: OK
+F_OK dangling nofollow: OK
+F_OK dangling follow: No such file or directory
+F_OK symlink eaccess|nofollow: OK