[libc] Switch sys/stat implementations over to libc_errno.

libc/src/sys/stat/linux/CMakeLists.txt

add_header_library(
   kernel_statx
   HDRS
     kernel_statx.h
   DEPENDS
     libc.include.sys_stat
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.__support.common
-    libc.src.errno.errno
 )
 
 add_entrypoint_object(
   stat
   SRCS
     stat.cpp
   HDRS
     ../stat.h
   DEPENDS
     .kernel_statx
     libc.include.fcntl
     libc.include.sys_stat
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
   lstat
   SRCS
     lstat.cpp
   HDRS
     ../lstat.h
   DEPENDS
     .kernel_statx
     libc.include.fcntl
     libc.include.sys_stat
+    libc.src.errno.errno
 )
 
 add_entrypoint_object(
   fstat
   SRCS
     fstat.cpp
   HDRS
     ../fstat.h
   DEPENDS
     .kernel_statx
     libc.include.fcntl
     libc.include.sys_stat
+    libc.src.errno.errno
 )

libc/src/sys/stat/linux/fstat.cpp

 //===-- Linux implementation of fstat -------------------------------------===//
 //
 // 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/sys/stat/fstat.h"
 #include "kernel_statx.h"
+#include "src/errno/libc_errno.h"
 
 #include "src/__support/common.h"
 
 #include <fcntl.h>
 #include <sys/stat.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fstat, (int fd, struct stat *statbuf)) {
-  return statx(fd, "", AT_EMPTY_PATH, statbuf);
+  int err = statx(fd, "", AT_EMPTY_PATH, statbuf);
+  if (err != 0) {
+    libc_errno = err;
+    return -1;
+  }
+  return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/kernel_statx.h

 //===-- Wrapper over SYS_statx syscall ------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIBC_SRC_SYS_STAT_LINUX_STATX_H
 #define LLVM_LIBC_SRC_SYS_STAT_LINUX_STATX_H
 
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
-#include <errno.h>
 #include <stdint.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 // It is safe to include this kernel header as it is designed to be
 // included from user programs without causing any name pollution.
 #include <linux/kdev_t.h>
 

 namespace __llvm_libc {
 
 LIBC_INLINE int statx(int dirfd, const char *__restrict path, int flags,
                       struct stat *__restrict statbuf) {
   // We make a statx syscall and copy out the result into the |statbuf|.
   ::statx_buf xbuf;
   long ret = __llvm_libc::syscall_impl(SYS_statx, dirfd, path, flags,
                                        ::STATX_BASIC_STATS_MASK, &xbuf);
-  if (ret < 0) {
-    errno = -ret;
-    return -1;
-  }
+  if (ret < 0)
+    return -ret;
 
   statbuf->st_dev = MKDEV(xbuf.stx_dev_major, xbuf.stx_dev_minor);
   statbuf->st_ino = xbuf.stx_ino;
   statbuf->st_mode = xbuf.stx_mode;
   statbuf->st_nlink = xbuf.stx_nlink;
   statbuf->st_uid = xbuf.stx_uid;
   statbuf->st_gid = xbuf.stx_gid;
   statbuf->st_rdev = MKDEV(xbuf.stx_rdev_major, xbuf.stx_rdev_minor);

libc/src/sys/stat/linux/lstat.cpp

 //===-- Linux implementation of lstat -------------------------------------===//
 //
 // 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/sys/stat/lstat.h"
 #include "kernel_statx.h"
+#include "src/errno/libc_errno.h"
 
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <fcntl.h>
 #include <sys/stat.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, lstat,
                    (const char *__restrict path,
                     struct stat *__restrict statbuf)) {
-  return statx(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW, statbuf);
+  int err = statx(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW, statbuf);
+  if (err != 0) {
+    libc_errno = err;
+    return -1;
+  }
+  return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/stat.cpp

 //===-- Linux implementation of stat --------------------------------------===//
 //
 // 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/sys/stat/stat.h"
 #include "kernel_statx.h"
+#include "src/errno/libc_errno.h"
 
 #include "src/__support/common.h"
 
 #include <fcntl.h>
 #include <sys/stat.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, stat,
                    (const char *__restrict path,
                     struct stat *__restrict statbuf)) {
-  return statx(AT_FDCWD, path, 0, statbuf);
+  int err = statx(AT_FDCWD, path, 0, statbuf);
+  if (err != 0) {
+    libc_errno = err;
+    return -1;
+  }
+  return 0;
 }
 
 } // namespace __llvm_libc

libc/test/src/sys/stat/lstat_test.cpp

 //===-- Unittests for lstat -----------------------------------------------===//
 //
 // 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/errno/libc_errno.h"
 #include "src/fcntl/open.h"
 #include "src/sys/stat/lstat.h"
 #include "src/unistd/close.h"
 #include "src/unistd/unlink.h"
 #include "test/ErrnoSetterMatcher.h"
 #include "test/UnitTest/Test.h"
 #include "utils/testutils/FDReader.h"
 
-#include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 
 TEST(LlvmLibcLStatTest, CreatAndReadMode) {
   using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
   using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
 
   // The test file is initially writable. We open it for writing and ensure
   // that it indeed can be opened for writing. Next, we close the file and
   // make it readonly using chmod. We test that chmod actually succeeded by
   // trying to open the file for writing and failing.
   constexpr const char *TEST_FILE = "testdata/lstat.test";
-  errno = 0;
+  libc_errno = 0;
 
   int fd = __llvm_libc::open(TEST_FILE, O_CREAT | O_WRONLY, S_IRWXU);
   ASSERT_GT(fd, 0);
-  ASSERT_EQ(errno, 0);
+  ASSERT_EQ(libc_errno, 0);
   ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
 
   struct stat statbuf;
   ASSERT_THAT(__llvm_libc::lstat(TEST_FILE, &statbuf), Succeeds(0));
 
   ASSERT_EQ(int(statbuf.st_mode), int(S_IRWXU | S_IFREG));
 
   ASSERT_THAT(__llvm_libc::unlink(TEST_FILE), Succeeds(0));
 }
 
 TEST(LlvmLibcLStatTest, NonExistentFile) {
-  errno = 0;
+  libc_errno = 0;
   using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
   struct stat statbuf;
   ASSERT_THAT(__llvm_libc::lstat("non-existent-file", &statbuf), Fails(ENOENT));
-  errno = 0;
+  libc_errno = 0;
 }