Add support for AT_REMOVEDIR in unlinkat syscall (emscripten-core#6466)

src/library_syscall.js

@@ -1174,9 +1174,14 @@ var SyscallsLibrary = {
     Module.printErr('warning: untested syscall');
 #endif
     var dirfd = SYSCALLS.get(), path = SYSCALLS.getStr(), flags = SYSCALLS.get();
-    assert(flags === 0);
     path = SYSCALLS.calculateAt(dirfd, path);
-    FS.unlink(path);
+    if (flags === 0) {
+      FS.unlink(path);
+    } else if (flags === {{{ cDefine('AT_REMOVEDIR') }}}) {
+      FS.rmdir(path);
+    } else {
+      abort('Invalid flags passed to unlinkat');
+    }
     return 0;
   },
   __syscall302: function(which, varargs) { // renameat

src/struct_info.json

@@ -135,7 +135,8 @@
             "F_SETLK", 
             "O_WRONLY",
             "AT_FDCWD",
-            "AT_SYMLINK_NOFOLLOW"
+            "AT_SYMLINK_NOFOLLOW",
+            "AT_REMOVEDIR"
         ],
         "structs": {
             "flock": [

tests/other/unlink/test.cpp

@@ -0,0 +1,47 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+int main() {
+  const char *filename = "test.dat";
+  const char *dirname = "test";
+
+  // Create a file
+  FILE *f = fopen(filename, "wb");
+  if (f == NULL) {
+    return 1;
+  }
+  if (fclose(f)) {
+    return 1;
+  }
+  // Check it exists
+  if (access(filename, F_OK) != 0) {
+    return 1;
+  }
+  // Delete the file
+  if (unlinkat(AT_FDCWD, filename, 0)) {
+    return 1;
+  }
+  // Check that it doesn't exist
+  if (access(filename, F_OK) != -1) {
+    return 1;
+  }
+
+  // Create a directory
+  if (mkdir(dirname, 0700)) {
+    return 1;
+  }
+  // Delete the directory
+  if (unlinkat(AT_FDCWD, dirname, AT_REMOVEDIR)) {
+    return 1;
+  }
+  // Check that it doesn't exist
+  if (access(dirname, F_OK) != -1) {
+    return 1;
+  }
+
+  printf("ok\n");
+
+  return 0;
+}

tests/other/unlink/test.out

@@ -0,0 +1 @@
+ok

tests/test_other.py

@@ -3800,6 +3800,9 @@ def test_init_file_at_offset(self):
     Popen([PYTHON, EMCC, 'src.cpp']).communicate()
     self.assertContained('read: 0\nfile size is 104\n', run_js('a.out.js'))
 
+  def test_unlink(self):
+    self.do_other_test(os.path.join('other', 'unlink'))
+
   def test_argv0_node(self):
     open('code.cpp', 'w').write(r'''
 #include <stdio.h>