[libc-commits] [libc] [libc] Add the implementation of the fdopen function (PR #94186)

Xu Zhang via libc-commits libc-commits at lists.llvm.org
Tue Jun 4 08:52:46 PDT 2024


https://github.com/simonzgx updated https://github.com/llvm/llvm-project/pull/94186

>From 6460fbaed3017c2de20e8d1d39b6431315ed81ca Mon Sep 17 00:00:00 2001
From: Xu Zhang <simonzgx at gmail.com>
Date: Tue, 4 Jun 2024 01:54:59 +0800
Subject: [PATCH 1/2] [libc] Add the implementation of the fdopen function

---
 libc/config/linux/aarch64/entrypoints.txt |  1 +
 libc/config/linux/riscv/entrypoints.txt   |  1 +
 libc/config/linux/x86_64/entrypoints.txt  |  1 +
 libc/spec/posix.td                        |  5 ++
 libc/src/fcntl/linux/fcntl.cpp            | 13 ++--
 libc/src/stdio/CMakeLists.txt             |  7 ++
 libc/src/stdio/fdopen.h                   | 20 ++++++
 libc/src/stdio/linux/CMakeLists.txt       | 15 +++++
 libc/src/stdio/linux/fdopen.cpp           | 79 +++++++++++++++++++++++
 libc/test/src/fcntl/fcntl_test.cpp        | 10 +++
 libc/test/src/stdio/CMakeLists.txt        | 14 ++++
 libc/test/src/stdio/fdopen_test.cpp       | 68 +++++++++++++++++++
 12 files changed, 230 insertions(+), 4 deletions(-)
 create mode 100644 libc/src/stdio/fdopen.h
 create mode 100644 libc/src/stdio/linux/fdopen.cpp
 create mode 100644 libc/test/src/stdio/fdopen_test.cpp

diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index ca0418c3618ae..81d14271547dc 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -201,6 +201,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.snprintf
     libc.src.stdio.vsprintf
     libc.src.stdio.vsnprintf
+    libc.src.stdio.fdopen
     #libc.src.stdio.sscanf
     #libc.src.stdio.scanf
     #libc.src.stdio.fscanf
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index 479af40b5b26b..fc5300f9be2d0 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -209,6 +209,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.sscanf
     libc.src.stdio.scanf
     libc.src.stdio.fscanf
+    libc.src.stdio.fdopen
 
     # sys/mman.h entrypoints
     libc.src.sys.mman.madvise
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 367db7d384d23..e607d69748e12 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -215,6 +215,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.scanf
     libc.src.stdio.fscanf
     libc.src.stdio.fileno
+    libc.src.stdio.fdopen
 
     # sys/epoll.h entrypoints
     libc.src.sys.epoll.epoll_create
diff --git a/libc/spec/posix.td b/libc/spec/posix.td
index e16353b8142de..78d9d727ac7b4 100644
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -1293,6 +1293,11 @@ def POSIX : StandardSpec<"POSIX"> {
             RetValSpec<IntType>,
             [ArgSpec<FILEPtr>]
           >,
+          FunctionSpec<
+            "fdopen",
+            RetValSpec<FILEPtr>,
+            [ArgSpec<IntType>, ArgSpec<ConstCharPtr>]
+          >,
       ]
   >;
 
diff --git a/libc/src/fcntl/linux/fcntl.cpp b/libc/src/fcntl/linux/fcntl.cpp
index 24a20fb364109..4100ec4298a20 100644
--- a/libc/src/fcntl/linux/fcntl.cpp
+++ b/libc/src/fcntl/linux/fcntl.cpp
@@ -29,8 +29,6 @@ LLVM_LIBC_FUNCTION(int, fcntl, (int fd, int cmd, ...)) {
   va_end(varargs);
 
   switch (cmd) {
-  case F_SETLKW:
-    return syscall_impl<int>(SYS_fcntl, fd, cmd, arg);
   case F_OFD_SETLKW: {
     struct flock *flk = reinterpret_cast<struct flock *>(arg);
     // convert the struct to a flock64
@@ -86,8 +84,15 @@ LLVM_LIBC_FUNCTION(int, fcntl, (int fd, int cmd, ...)) {
     return -1;
   }
   // The general case
-  default:
-    return syscall_impl<int>(SYS_fcntl, fd, cmd, reinterpret_cast<void *>(arg));
+  default: {
+    int retVal =
+        syscall_impl<int>(SYS_fcntl, fd, cmd, reinterpret_cast<void *>(arg));
+    if (retVal >= 0) {
+      return retVal;
+    }
+    libc_errno = -retVal;
+    return -1;
+  }
   }
 }
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdio/CMakeLists.txt b/libc/src/stdio/CMakeLists.txt
index 1056f38fc7513..deb7e5ad942bf 100644
--- a/libc/src/stdio/CMakeLists.txt
+++ b/libc/src/stdio/CMakeLists.txt
@@ -263,6 +263,13 @@ add_entrypoint_object(
     .${LIBC_TARGET_OS}.rename
 )
 
+add_entrypoint_object(
+  fdopen
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.fdopen
+)
+
 # These entrypoints have multiple potential implementations.
 add_stdio_entrypoint_object(feof)
 add_stdio_entrypoint_object(feof_unlocked)
diff --git a/libc/src/stdio/fdopen.h b/libc/src/stdio/fdopen.h
new file mode 100644
index 0000000000000..158a133e7e131
--- /dev/null
+++ b/libc/src/stdio/fdopen.h
@@ -0,0 +1,20 @@
+//===-- Implementation header of open ---------------------------*- C++ -*-===//
+//
+// 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_STDIO_FDOPEN_H
+#define LLVM_LIBC_SRC_STDIO_FDOPEN_H
+
+#include <stdio.h>
+
+namespace LIBC_NAMESPACE {
+
+FILE *fdopen(int fd, const char *mode);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDIO_FDOPEN_H
diff --git a/libc/src/stdio/linux/CMakeLists.txt b/libc/src/stdio/linux/CMakeLists.txt
index a08ff0ba4832f..fe8b529d094fb 100644
--- a/libc/src/stdio/linux/CMakeLists.txt
+++ b/libc/src/stdio/linux/CMakeLists.txt
@@ -24,3 +24,18 @@ add_entrypoint_object(
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
+
+add_entrypoint_object(
+  fdopen
+  SRCS
+    fdopen.cpp
+  HDRS
+    ../fdopen.h
+  DEPENDS
+    libc.include.fcntl
+    libc.include.stdio
+    libc.src.errno.errno
+    libc.src.fcntl.fcntl
+    libc.src.stdio.fseek
+    libc.src.__support.File.linux.file
+)
\ No newline at end of file
diff --git a/libc/src/stdio/linux/fdopen.cpp b/libc/src/stdio/linux/fdopen.cpp
new file mode 100644
index 0000000000000..2f4c69f58b92d
--- /dev/null
+++ b/libc/src/stdio/linux/fdopen.cpp
@@ -0,0 +1,79 @@
+//===-- Implementation of fprintf -------------------------------*- C++ -*-===//
+//
+// 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/stdio/fdopen.h"
+
+#include "include/llvm-libc-macros/generic-error-number-macros.h"
+#include "include/llvm-libc-macros/linux/fcntl-macros.h"
+#include "src/__support/File/linux/file.h"
+#include "src/errno/libc_errno.h"
+#include "src/fcntl/fcntl.h"
+#include "src/stdio/fseek.h"
+
+#include <stdio.h>
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(::FILE *, fdopen, (int fd, const char *mode)) {
+  using ModeFlags = File::ModeFlags;
+  ModeFlags modeflags = File::mode_flags(mode);
+  if (modeflags == 0) {
+    libc_errno = EINVAL;
+    return nullptr;
+  }
+
+  int fd_flags = LIBC_NAMESPACE::fcntl(fd, F_GETFL);
+  if (fd_flags == -1) {
+    return nullptr;
+  }
+
+  using OpenMode = File::OpenMode;
+  if (((fd_flags & O_ACCMODE) == O_RDONLY &&
+       !(modeflags & static_cast<ModeFlags>(OpenMode::READ))) ||
+      ((fd_flags & O_ACCMODE) == O_WRONLY &&
+       !(modeflags & static_cast<ModeFlags>(OpenMode::WRITE)))) {
+    libc_errno = EINVAL;
+    return nullptr;
+  }
+
+  bool do_seek = false;
+  if ((modeflags & static_cast<ModeFlags>(OpenMode::APPEND)) &&
+      !(fd_flags & O_APPEND)) {
+    do_seek = true;
+    if (LIBC_NAMESPACE::fcntl(fd, F_SETFL, fd_flags | O_APPEND) == -1) {
+      libc_errno = EBADF;
+      return nullptr;
+    }
+  }
+
+  uint8_t *buffer;
+  {
+    AllocChecker ac;
+    buffer = new (ac) uint8_t[File::DEFAULT_BUFFER_SIZE];
+    if (!ac) {
+      libc_errno = ENOMEM;
+      return nullptr;
+    }
+  }
+  AllocChecker ac;
+  auto *linux_file = new (ac)
+      LinuxFile(fd, buffer, File::DEFAULT_BUFFER_SIZE, _IOFBF, true, modeflags);
+  if (!ac) {
+    libc_errno = ENOMEM;
+    return nullptr;
+  }
+  auto *file = reinterpret_cast<::FILE *>(linux_file);
+  if (do_seek && LIBC_NAMESPACE::fseek(file, 0, SEEK_END) != 0) {
+    free(linux_file);
+    return nullptr;
+  }
+
+  return file;
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/test/src/fcntl/fcntl_test.cpp b/libc/test/src/fcntl/fcntl_test.cpp
index c5cbb61b4ed8a..e0641b2e3fc6b 100644
--- a/libc/test/src/fcntl/fcntl_test.cpp
+++ b/libc/test/src/fcntl/fcntl_test.cpp
@@ -153,3 +153,13 @@ TEST(LlvmLibcFcntlTest, FcntlGetLkWrite) {
 
   ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
 }
+
+TEST(LlvmLibcFcntlTest, UseAfterClose) {
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_FILE_NAME = "testdata/fcntl_use_after_close.test";
+  auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDWR, S_IRWXU);
+  ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds(0));
+  ASSERT_EQ(-1, LIBC_NAMESPACE::fcntl(fd, F_GETFL));
+  ASSERT_ERRNO_EQ(EBADF);
+}
\ No newline at end of file
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
index 03c43eaefebe5..45f3147089d06 100644
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -369,6 +369,20 @@ if(${LIBC_TARGET_OS} STREQUAL "linux")
       libc.src.unistd.close
       libc.test.UnitTest.ErrnoSetterMatcher
   )
+
+  add_libc_test(
+    fdopen_test
+    SUITE
+      libc_stdio_unittests
+    SRCS
+      fdopen_test.cpp
+    DEPENDS
+      libc.src.fcntl.open
+      libc.src.stdio.fclose
+      libc.src.stdio.fdopen
+      libc.src.unistd.close
+      libc.test.UnitTest.ErrnoSetterMatcher
+  )
 endif()
 
 add_libc_test(
diff --git a/libc/test/src/stdio/fdopen_test.cpp b/libc/test/src/stdio/fdopen_test.cpp
new file mode 100644
index 0000000000000..399321b2bf8c8
--- /dev/null
+++ b/libc/test/src/stdio/fdopen_test.cpp
@@ -0,0 +1,68 @@
+//===-- Unittest for fcntl ------------------------------------------------===//
+//
+// 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 "include/llvm-libc-macros/linux/fcntl-macros.h"
+#include "src/stdio/fdopen.h"
+
+#include "src/errno/libc_errno.h"
+#include "src/fcntl/fcntl.h"
+#include "src/fcntl/open.h"
+#include "src/stdio/fclose.h"
+#include "src/unistd/close.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/LibcTest.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/stat.h> // For S_IRWXU
+
+TEST(LlvmLibcStdioFdopenTest, InvalidInput) {
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+  LIBC_NAMESPACE::libc_errno = 0;
+  constexpr const char *TEST_FILE_NAME = "testdata/fdopen_invalid_inputs.test";
+  auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
+  auto *fp = LIBC_NAMESPACE::fdopen(fd, "m+");
+  ASSERT_ERRNO_EQ(EINVAL);
+  ASSERT_TRUE(nullptr == fp);
+  LIBC_NAMESPACE::close(fd);
+  LIBC_NAMESPACE::libc_errno = 0;
+  fp = LIBC_NAMESPACE::fdopen(fd, "r");
+  ASSERT_ERRNO_EQ(EBADF);
+  ASSERT_TRUE(nullptr == fp);
+}
+
+TEST(LlvmLibcStdioFdopenTest, InvalidMode) {
+  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+  LIBC_NAMESPACE::libc_errno = 0;
+  constexpr const char *TEST_FILE_NAME = "testdata/fdopen_invid_mode.test";
+  auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GT(fd, 0);
+  auto *fp = LIBC_NAMESPACE::fdopen(fd, "r+");
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_TRUE(nullptr != fp);
+  ASSERT_THAT(LIBC_NAMESPACE::fclose(fp), Succeeds(0));
+  // If the mode argument is invalid, then `fdopen` returns a nullptr and sets
+  // the `errno` to EINVAL. In this case the `mode` param can only be "r" or
+  // "r+"
+  int fd2 = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_GT(fd2, 0);
+  auto *fp2 = LIBC_NAMESPACE::fdopen(fd2, "w");
+  ASSERT_ERRNO_EQ(EINVAL);
+  ASSERT_TRUE(nullptr == fp2);
+}
+
+TEST(LlvmLibcStdioFdopenTest, WriteRead) {
+
+}
+
+TEST(LlvmLibcStdioFdopenTest, Append) {}
+
+TEST(LlvmLibcStdioFdopenTest, AppendPlus) {}
\ No newline at end of file

>From 7d86b4d29720bd129ce636249ed46704572df69c Mon Sep 17 00:00:00 2001
From: Xu Zhang <simonzgx at gmail.com>
Date: Tue, 4 Jun 2024 23:52:28 +0800
Subject: [PATCH 2/2] Update unit test

---
 libc/src/stdio/linux/fdopen.cpp     |  1 -
 libc/test/src/stdio/CMakeLists.txt  |  2 +
 libc/test/src/stdio/fdopen_test.cpp | 77 ++++++++++++++++++-----------
 3 files changed, 51 insertions(+), 29 deletions(-)

diff --git a/libc/src/stdio/linux/fdopen.cpp b/libc/src/stdio/linux/fdopen.cpp
index 2f4c69f58b92d..6d35e68853917 100644
--- a/libc/src/stdio/linux/fdopen.cpp
+++ b/libc/src/stdio/linux/fdopen.cpp
@@ -46,7 +46,6 @@ LLVM_LIBC_FUNCTION(::FILE *, fdopen, (int fd, const char *mode)) {
       !(fd_flags & O_APPEND)) {
     do_seek = true;
     if (LIBC_NAMESPACE::fcntl(fd, F_SETFL, fd_flags | O_APPEND) == -1) {
-      libc_errno = EBADF;
       return nullptr;
     }
   }
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
index 45f3147089d06..5eb8c9577893b 100644
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -380,6 +380,8 @@ if(${LIBC_TARGET_OS} STREQUAL "linux")
       libc.src.fcntl.open
       libc.src.stdio.fclose
       libc.src.stdio.fdopen
+      libc.src.stdio.fgets
+      libc.src.stdio.fputs
       libc.src.unistd.close
       libc.test.UnitTest.ErrnoSetterMatcher
   )
diff --git a/libc/test/src/stdio/fdopen_test.cpp b/libc/test/src/stdio/fdopen_test.cpp
index 399321b2bf8c8..4cf693a0d9d01 100644
--- a/libc/test/src/stdio/fdopen_test.cpp
+++ b/libc/test/src/stdio/fdopen_test.cpp
@@ -10,9 +10,10 @@
 #include "src/stdio/fdopen.h"
 
 #include "src/errno/libc_errno.h"
-#include "src/fcntl/fcntl.h"
 #include "src/fcntl/open.h"
 #include "src/stdio/fclose.h"
+#include "src/stdio/fgets.h"
+#include "src/stdio/fputs.h"
 #include "src/unistd/close.h"
 #include "test/UnitTest/ErrnoSetterMatcher.h"
 #include "test/UnitTest/LibcTest.h"
@@ -20,49 +21,69 @@
 
 #include <sys/stat.h> // For S_IRWXU
 
-TEST(LlvmLibcStdioFdopenTest, InvalidInput) {
+TEST(LlvmLibcStdioFdopenTest, WriteAppendRead) {
   using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
   LIBC_NAMESPACE::libc_errno = 0;
-  constexpr const char *TEST_FILE_NAME = "testdata/fdopen_invalid_inputs.test";
+  constexpr const char *TEST_FILE_NAME = "testdata/write_read_append.test";
   auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
-  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
-  auto *fp = LIBC_NAMESPACE::fdopen(fd, "m+");
-  ASSERT_ERRNO_EQ(EINVAL);
-  ASSERT_TRUE(nullptr == fp);
-  LIBC_NAMESPACE::close(fd);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDWR, S_IRWXU);
+  auto *fp = LIBC_NAMESPACE::fdopen(fd, "w");
+  ASSERT_ERRNO_SUCCESS();
+  ASSERT_TRUE(nullptr != fp);
+  constexpr const char HELLO[] = "Hello";
+  LIBC_NAMESPACE::fputs(HELLO, fp);
+  LIBC_NAMESPACE::fclose(fp);
+  ASSERT_ERRNO_SUCCESS();
+
+  constexpr const char LLVM[] = "LLVM";
+  int fd2 = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_RDWR);
+  auto *fp2 = LIBC_NAMESPACE::fdopen(fd2, "a");
+  LIBC_NAMESPACE::fputs(LLVM, fp2);
+  LIBC_NAMESPACE::fclose(fp2);
+  ASSERT_ERRNO_SUCCESS();
+
+  int fd3 = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_RDWR);
+  auto *fp3 = LIBC_NAMESPACE::fdopen(fd3, "r");
+  char buffer[10];
+  LIBC_NAMESPACE::fgets(buffer, sizeof(buffer), fp3);
+  EXPECT_EQ('H', buffer[0]);
+  EXPECT_EQ('M', buffer[8]);
+  LIBC_NAMESPACE::fclose(fp3);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcStdioFdopenTest, InvalidFd) {
   LIBC_NAMESPACE::libc_errno = 0;
-  fp = LIBC_NAMESPACE::fdopen(fd, "r");
+  constexpr const char *TEST_FILE_NAME = "testdata/invalid_fd.test";
+  auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC);
+  LIBC_NAMESPACE::close(fd);
+  // With `fd` already closed, `fdopen` should fail and set the `errno` to EBADF
+  auto *fp = LIBC_NAMESPACE::fdopen(fd, "r");
   ASSERT_ERRNO_EQ(EBADF);
   ASSERT_TRUE(nullptr == fp);
 }
 
 TEST(LlvmLibcStdioFdopenTest, InvalidMode) {
-  using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
   LIBC_NAMESPACE::libc_errno = 0;
-  constexpr const char *TEST_FILE_NAME = "testdata/fdopen_invid_mode.test";
+  constexpr const char *TEST_FILE_NAME = "testdata/invalid_mode.test";
   auto TEST_FILE = libc_make_test_file_path(TEST_FILE_NAME);
-  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
+  int fd = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_RDONLY, S_IRWXU);
   ASSERT_ERRNO_SUCCESS();
   ASSERT_GT(fd, 0);
-  auto *fp = LIBC_NAMESPACE::fdopen(fd, "r+");
-  ASSERT_ERRNO_SUCCESS();
-  ASSERT_TRUE(nullptr != fp);
-  ASSERT_THAT(LIBC_NAMESPACE::fclose(fp), Succeeds(0));
+
+  // `Mode` must be one of "r", "w" or "a"
+  auto *fp = LIBC_NAMESPACE::fdopen(fd, "m+");
+  ASSERT_ERRNO_EQ(EINVAL);
+  ASSERT_TRUE(nullptr == fp);
+
   // If the mode argument is invalid, then `fdopen` returns a nullptr and sets
   // the `errno` to EINVAL. In this case the `mode` param can only be "r" or
   // "r+"
-  int fd2 = LIBC_NAMESPACE::open(TEST_FILE, O_CREAT | O_TRUNC | O_RDONLY);
-  ASSERT_ERRNO_SUCCESS();
-  ASSERT_GT(fd2, 0);
-  auto *fp2 = LIBC_NAMESPACE::fdopen(fd2, "w");
+  auto *fp2 = LIBC_NAMESPACE::fdopen(fd, "w");
   ASSERT_ERRNO_EQ(EINVAL);
   ASSERT_TRUE(nullptr == fp2);
+  LIBC_NAMESPACE::libc_errno = 0;
+  LIBC_NAMESPACE::close(fd);
+  ASSERT_ERRNO_SUCCESS();
 }
-
-TEST(LlvmLibcStdioFdopenTest, WriteRead) {
-
-}
-
-TEST(LlvmLibcStdioFdopenTest, Append) {}
-
-TEST(LlvmLibcStdioFdopenTest, AppendPlus) {}
\ No newline at end of file



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