[libc] Add the implementation of the "remove" function.

[lntue]

libc/src/stdio/linux/remove.cpp

24

In the implementation of linux/unlinkat, SYS_unlinkat is guarded: https://github.com/llvm/llvm-project/blob/main/libc/src/unistd/linux/unlinkat.cpp#L21
Do you need the same guard here?

[sivachandra]

libc/src/stdio/linux/remove.cpp

24

I think that example is being a bit too pedantic. We can remove it - if SYS_unlinkat is missing, there will be a compile failure providing equivalent information.

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     # stdlib.h external entrypoints
     libc.src.stdlib.malloc
     libc.src.stdlib.calloc
     libc.src.stdlib.realloc
     libc.src.stdlib.aligned_alloc
     libc.src.stdlib.free
 
     # stdio.h entrypoints
+    libc.src.stdio.remove
     libc.src.stdio.sprintf
     libc.src.stdio.snprintf
 
     # sys/mman.h entrypoints
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap
 
     # sys/sendfile entrypoints

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     # stdlib.h external entrypoints
     libc.src.stdlib.malloc
     libc.src.stdlib.calloc
     libc.src.stdlib.realloc
     libc.src.stdlib.aligned_alloc
     libc.src.stdlib.free
 
     # stdio.h entrypoints
+    libc.src.stdio.remove
     libc.src.stdio.sprintf
     libc.src.stdio.snprintf
 
     # sys/mman.h entrypoints
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap
 
     # sys/sendfile entrypoints

libc/spec/stdc.td

HeaderSpec StdIO = HeaderSpec<
               "fwrite",
               RetValSpec<SizeTType>,
               [ArgSpec<ConstVoidRestrictedPtr>,
                ArgSpec<SizeTType>,
                ArgSpec<SizeTType>,
                ArgSpec<FILERestrictedPtr>]
           >,
           FunctionSpec<
+              "remove",
+              RetValSpec<IntType>,
+              [ArgSpec<ConstCharPtr>]
+          >,
+          FunctionSpec<
               "sprintf",
               RetValSpec<IntType>,
               [ArgSpec<CharRestrictedPtr>,
                ArgSpec<ConstCharRestrictedPtr>,
                ArgSpec<VarArgType>]
           >,
           FunctionSpec<
               "snprintf",

libc/src/stdio/CMakeLists.txt

+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
 add_subdirectory(printf_core)
 
 add_entrypoint_object(
   fopen
   SRCS
     fopen.cpp
   HDRS
     fopen.h
add_entrypoint_object(
   HDRS
     printf.h
   DEPENDS
     libc.src.__support.File.file
     libc.src.__support.File.platform_file
     libc.src.__support.arg_list
     libc.src.stdio.printf_core.vfprintf_internal
 )
+
+add_entrypoint_object(
+  remove
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.remove
+)

libc/src/stdio/linux/CMakeLists.txt

+add_entrypoint_object(
+  remove
+  SRCS
+    remove.cpp
+  HDRS
+    ../remove.h
+  DEPENDS
+    libc.include.fcntl
+    libc.include.unistd
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/stdio/linux/remove.cpp

+//===-- Linux implementation of remove ------------------------------------===//
+//
+// 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/remove.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <fcntl.h>       // For AT_* macros.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, remove, (const char *path)) {
+  // We first try unlinking it as a file. If it is ia file, it will succeed. If
+  // it fails with EISDIR, we will try unlinking it as a directory.
+  int ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, 0);
+  if (ret == -EISDIR)
+    ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
+  if (ret >= 0)
+    return 0;
+  errno = -ret;
+  return -1;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/remove.h

+//===-- Implementation header of remove -------------------------*- 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_REMOVE_H
+#define LLVM_LIBC_SRC_STDIO_REMOVE_H
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+int remove(const char *path);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STDIO_REMOVE_H

libc/test/src/stdio/CMakeLists.txt

SUITE
     libc_stdio_unittests
   SRCS
     printf_test.cpp
   DEPENDS
     libc.src.stdio.printf
     libc.src.fenv.fesetround
 )
 
-add_subdirectory(printf_core)
+add_libc_unittest(
+  remove_test
+  SUITE
+    libc_stdio_unittests
+  SRCS
+    remove_test.cpp
+  DEPENDS
+    libc.include.errno
+    libc.include.unistd
+    libc.src.fcntl.open
+    libc.src.stdio.remove
+    libc.src.sys.stat.mkdirat
+    libc.src.unistd.access
+    libc.src.unistd.close
+)
 
+add_subdirectory(printf_core)
 add_subdirectory(testdata)

libc/test/src/stdio/remove_test.cpp

+//===-- Unittests for remove ----------------------------------------------===//
+//
+// 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/fcntl/open.h"
+#include "src/stdio/remove.h"
+#include "src/sys/stat/mkdirat.h"
+#include "src/unistd/access.h"
+#include "src/unistd/close.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include "utils/testutils/FDReader.h"
+
+#include <errno.h>
+#include <unistd.h>
+
+TEST(LlvmLibcRemoveTest, CreateAndRemoveFile) {
+  // The test strategy is to create a file and remove it, and also verify that
+  // it was removed.
+  errno = 0;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_FILE = "testdata/remove.test.file";
+  int fd = __llvm_libc::open(TEST_FILE, O_WRONLY | O_CREAT, S_IRWXU);
+  ASSERT_EQ(errno, 0);
+  ASSERT_GT(fd, 0);
+  ASSERT_THAT(__llvm_libc::close(fd), Succeeds(0));
+
+  ASSERT_THAT(__llvm_libc::access(TEST_FILE, F_OK), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::remove(TEST_FILE), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::access(TEST_FILE, F_OK), Fails(ENOENT));
+}
+
+TEST(LlvmLibcRemoveTest, CreateAndRemoveDir) {
+  // The test strategy is to create a dir and remove it, and also verify that
+  // it was removed.
+  errno = 0;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+  constexpr const char *TEST_DIR = "testdata/remove.test.dir";
+  ASSERT_THAT(__llvm_libc::mkdirat(AT_FDCWD, TEST_DIR, S_IRWXU), Succeeds(0));
+
+  ASSERT_THAT(__llvm_libc::access(TEST_DIR, F_OK), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::remove(TEST_DIR), Succeeds(0));
+  ASSERT_THAT(__llvm_libc::access(TEST_DIR, F_OK), Fails(ENOENT));
+}
+
+TEST(LlvmLibcRemoveTest, RemoveNonExistent) {
+  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
+  ASSERT_THAT(__llvm_libc::remove("testdata/non-existent"), Fails(ENOENT));
+}