[libc-commits] [libc] [libc] implement pathconf/fpathconf (PR #87165)

[Schrodinger ZHU Yifan via libc-commits]

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@@ -0,0 +1,60 @@
+//===-- Linux implementation of fpathconf ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/fsync.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+static long pathconfig(const struct statvfs &s, int name) {
+  switch (name) {
+  case _PC_LINK_MAX:
+    return _POSIX_LINK_MAX;
+
+  case _PC_MAX_CANON:
+    return _POSIX_MAX_CANON;
+
+  case _PC_MAX_INPUT:
+    return _POSIX_MAX_INPUT;
+
+  case _PC_NAME_MAX:
+    return _POSIX_NAME_MAX;
+
+  case _PC_PATH_MAX:
+    return _POSIX_PATH_MAX;
+
+  case _PC_PIPE_BUF:
+    return _POSIX_PIPE_BUF;
+
+  case _PC_CHOWN_RESTRICTED:
+    return _POSIX_CHOWN_RESTRICTED;
+
+  case _PC_NO_TRUNC:
+    return _POSIX_NO_TRUNC;
+
+  case _PC_VDISABLE:
+    return _POSIX_VDISABLE;
----------------
SchrodingerZhu wrote:

AFAIK, not all fields are directly provided by `statfs`. You can just do the best estimation you have. For example, for name length, `statfs` give you the exact answer, so you can go ahead and use it. For other situation, you may just fallback to POSIX constants. https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/bionic/pathconf.cpp.

Some tedious parts are that you may need to take a look of the configuration per file system.

https://github.com/llvm/llvm-project/pull/87165