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[flang][runtime] Add ACCESS library procedure #88517

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merged 6 commits into from
Apr 16, 2024
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@tblah tblah commented Apr 12, 2024

Re-land #88395

Two build-bots were broken by the old version:

The problem in both cases was that the compiler did not support std::filesystem (which I use in the unit test).

I have removed the dependency upon std::filesystem because there isn't an easy way to add the right linker options so that this is supported correctly in all build environments [1]

[1] https://gitlab.kitware.com/cmake/cmake/-/issues/17834


This is a GNU extension:
https://gcc.gnu.org/onlinedocs/gfortran/ACCESS.html

Used in SALMON:
https://salmon-tddft.jp/download.html

Unfortunately the intrinsic takes a file path to operate on so there isn't an easy way to make the test robust. The unit test expects to be able to create, set read write and execute permissions, and delete files called
std::filesystem::temp_directory_path() / <test_name>.

The test will fail if a file already exists with that name.

I have not implemented the intrinsic on Windows because this is wrapping a POSIX system call and Windows doesn't support all of the permission bits tested by the intrinsic. I don't have a Windows machine easily available to check if Gfortran implements this intrinsic on Windows.

This is a GNU extension:
https://gcc.gnu.org/onlinedocs/gfortran/ACCESS.html

Used in SALMON:
https://salmon-tddft.jp/download.html

Unfortunately the intrinsic takes a file path to operate on so there
isn't an easy way to make the test robust. The unit test expects to be
able to create, set read write and execute permissions, and delete
files called
  std::filesystem::temp_directory_path() / <test_name>.<pid>

The test will fail if a file already exists with that name.

I have not implemented the intrinsic on Windows because this is wrapping
a POSIX system call and Windows doesn't support all of the permission
bits tested by the intrinsic. I don't have a Windows machine easily
available to check if Gfortran implements this intrinsic on Windows.
I didn't apply braced initialization to very common C programming
patterns in the unittest because when something is extremely common, I
think it increases cognitive load when reading. For example
  int fd = open(...);
vs
  int fd{open(...)};

I did change all uses in the runtime implementation as requested in code
review.
@llvmbot llvmbot added flang:runtime flang Flang issues not falling into any other category labels Apr 12, 2024
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llvmbot commented Apr 12, 2024

@llvm/pr-subscribers-flang-runtime

Author: Tom Eccles (tblah)

Changes

Re-land #88395

Two build-bots were broken by the old version:

The problem in both cases was that the compiler did not support std::filesystem (which I use in the unit test).

I believe that flang already requires a compiler capable of c++ 17 so this should be okay. I have adjusted CMake in 66f32b5 so that hopefully std::filesystem will be linked for those compilers. However, I am worried that linking stdc++fs, could break some other platform. CMake does not appear to have any built in magic to do the right thing [1].

Another alternative would be to rewrite the unit test not to use std::filesystem. I would prefer to avoid this so that I don't have to add a manual implementation of std::filesystem::temp_directory_path(), as that might be a pain point when porting flang to new systems.

[1] https://gitlab.kitware.com/cmake/cmake/-/issues/17834


This is a GNU extension:
https://gcc.gnu.org/onlinedocs/gfortran/ACCESS.html

Used in SALMON:
https://salmon-tddft.jp/download.html

Unfortunately the intrinsic takes a file path to operate on so there isn't an easy way to make the test robust. The unit test expects to be able to create, set read write and execute permissions, and delete files called
std::filesystem::temp_directory_path() / <test_name>.<pid>

The test will fail if a file already exists with that name.

I have not implemented the intrinsic on Windows because this is wrapping a POSIX system call and Windows doesn't support all of the permission bits tested by the intrinsic. I don't have a Windows machine easily available to check if Gfortran implements this intrinsic on Windows.


Full diff: https://github.com/llvm/llvm-project/pull/88517.diff

5 Files Affected:

  • (modified) flang/docs/Intrinsics.md (+8)
  • (modified) flang/include/flang/Runtime/extensions.h (+7)
  • (modified) flang/runtime/extensions.cpp (+73)
  • (added) flang/unittests/Runtime/AccessTest.cpp (+390)
  • (modified) flang/unittests/Runtime/CMakeLists.txt (+4)
diff --git a/flang/docs/Intrinsics.md b/flang/docs/Intrinsics.md
index ccb93e104dab65..848619cb65d909 100644
--- a/flang/docs/Intrinsics.md
+++ b/flang/docs/Intrinsics.md
@@ -657,6 +657,14 @@ CALL CO_REDUCE
 CALL CO_SUM
 ```
 
+### Inquiry Functions
+ACCESS (GNU extension) is not supported on Windows. Otherwise:
+```
+CHARACTER(LEN=*) :: path = 'path/to/file'
+IF (ACCESS(path, 'rwx')) &
+  ...
+```
+
 ## Non-standard intrinsics
 ### PGI
 ```
diff --git a/flang/include/flang/Runtime/extensions.h b/flang/include/flang/Runtime/extensions.h
index 7d0952206fc195..fef651f3b2eedb 100644
--- a/flang/include/flang/Runtime/extensions.h
+++ b/flang/include/flang/Runtime/extensions.h
@@ -44,5 +44,12 @@ std::int64_t RTNAME(Signal)(std::int64_t number, void (*handler)(int));
 // GNU extension subroutine SLEEP(SECONDS)
 void RTNAME(Sleep)(std::int64_t seconds);
 
+// GNU extension function ACCESS(NAME, MODE)
+// TODO: not supported on Windows
+#ifndef _WIN32
+std::int64_t FORTRAN_PROCEDURE_NAME(access)(const char *name,
+    std::int64_t nameLength, const char *mode, std::int64_t modeLength);
+#endif
+
 } // extern "C"
 #endif // FORTRAN_RUNTIME_EXTENSIONS_H_
diff --git a/flang/runtime/extensions.cpp b/flang/runtime/extensions.cpp
index 3ac98000335d7d..12498b502ae1cf 100644
--- a/flang/runtime/extensions.cpp
+++ b/flang/runtime/extensions.cpp
@@ -17,6 +17,7 @@
 #include "flang/Runtime/entry-names.h"
 #include "flang/Runtime/io-api.h"
 #include <chrono>
+#include <cstring>
 #include <ctime>
 #include <signal.h>
 #include <thread>
@@ -138,5 +139,77 @@ void RTNAME(Sleep)(std::int64_t seconds) {
   std::this_thread::sleep_for(std::chrono::seconds(seconds));
 }
 
+// TODO: not supported on Windows
+#ifndef _WIN32
+std::int64_t FORTRAN_PROCEDURE_NAME(access)(const char *name,
+    std::int64_t nameLength, const char *mode, std::int64_t modeLength) {
+  std::int64_t ret{-1};
+  if (nameLength <= 0 || modeLength <= 0 || !name || !mode) {
+    return ret;
+  }
+
+  // ensure name is null terminated
+  char *newName{nullptr};
+  if (name[nameLength - 1] != '\0') {
+    newName = static_cast<char *>(std::malloc(nameLength + 1));
+    std::memcpy(newName, name, nameLength);
+    newName[nameLength] = '\0';
+    name = newName;
+  }
+
+  // calculate mode
+  bool read{false};
+  bool write{false};
+  bool execute{false};
+  bool exists{false};
+  int imode{0};
+
+  for (std::int64_t i = 0; i < modeLength; ++i) {
+    switch (mode[i]) {
+    case 'r':
+      read = true;
+      break;
+    case 'w':
+      write = true;
+      break;
+    case 'x':
+      execute = true;
+      break;
+    case ' ':
+      exists = true;
+      break;
+    default:
+      // invalid mode
+      goto cleanup;
+    }
+  }
+  if (!read && !write && !execute && !exists) {
+    // invalid mode
+    goto cleanup;
+  }
+
+  if (!read && !write && !execute) {
+    imode = F_OK;
+  } else {
+    if (read) {
+      imode |= R_OK;
+    }
+    if (write) {
+      imode |= W_OK;
+    }
+    if (execute) {
+      imode |= X_OK;
+    }
+  }
+  ret = access(name, imode);
+
+cleanup:
+  if (newName) {
+    free(newName);
+  }
+  return ret;
+}
+#endif
+
 } // namespace Fortran::runtime
 } // extern "C"
diff --git a/flang/unittests/Runtime/AccessTest.cpp b/flang/unittests/Runtime/AccessTest.cpp
new file mode 100644
index 00000000000000..5c8a634192d92b
--- /dev/null
+++ b/flang/unittests/Runtime/AccessTest.cpp
@@ -0,0 +1,390 @@
+//===-- flang/unittests/Runtime/AccessTest.cpp ----------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// TODO: ACCESS is not yet implemented on Windows
+#ifndef _WIN32
+
+#include "CrashHandlerFixture.h"
+#include "gtest/gtest.h"
+#include "flang/Runtime/extensions.h"
+
+#include <fcntl.h>
+#include <filesystem>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+namespace {
+
+struct AccessTests : public CrashHandlerFixture {};
+
+struct AccessType {
+  bool read{false};
+  bool write{false};
+  bool execute{false};
+  bool exists{false};
+};
+
+} // namespace
+
+static std::string addPIDSuffix(const char *name) {
+  std::stringstream ss;
+  ss << name;
+  ss << '.';
+
+  ss << getpid();
+
+  return ss.str();
+}
+
+static std::filesystem::path createTemporaryFile(
+    const char *name, const AccessType &accessType) {
+  std::filesystem::path path{
+      std::filesystem::temp_directory_path() / addPIDSuffix(name)};
+
+  // O_CREAT | O_EXCL enforces that this file is newly created by this call.
+  // This feels risky. If we don't have permission to create files in the
+  // temporary directory or if the files already exist, the test will fail.
+  // But we can't use std::tmpfile() because we need a path to the file and
+  // to control the filesystem permissions
+  mode_t mode{0};
+  if (accessType.read) {
+    mode |= S_IRUSR;
+  }
+  if (accessType.write) {
+    mode |= S_IWUSR;
+  }
+  if (accessType.execute) {
+    mode |= S_IXUSR;
+  }
+
+  int file = open(path.c_str(), O_CREAT | O_EXCL, mode);
+  if (file == -1) {
+    return {};
+  }
+
+  close(file);
+
+  return path;
+}
+
+static std::int64_t callAccess(
+    const std::filesystem::path &path, const AccessType &accessType) {
+  const char *cpath{path.c_str()};
+  std::int64_t pathlen = std::strlen(cpath);
+
+  std::string mode;
+  if (accessType.read) {
+    mode += 'r';
+  }
+  if (accessType.write) {
+    mode += 'w';
+  }
+  if (accessType.execute) {
+    mode += 'x';
+  }
+  if (accessType.exists) {
+    mode += ' ';
+  }
+
+  const char *cmode = mode.c_str();
+  std::int64_t modelen = std::strlen(cmode);
+
+  return FORTRAN_PROCEDURE_NAME(access)(cpath, pathlen, cmode, modelen);
+}
+
+TEST(AccessTests, TestExists) {
+  AccessType accessType;
+  accessType.exists = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotExists) {
+  std::filesystem::path nonExistant{addPIDSuffix(__func__)};
+  ASSERT_FALSE(std::filesystem::exists(nonExistant));
+
+  AccessType accessType;
+  accessType.exists = true;
+  std::int64_t res = callAccess(nonExistant, accessType);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestRead) {
+  AccessType accessType;
+  accessType.read = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotRead) {
+  AccessType accessType;
+  accessType.read = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestWrite) {
+  AccessType accessType;
+  accessType.write = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotWrite) {
+  AccessType accessType;
+  accessType.write = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.write = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestReadWrite) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotReadWrite0) {
+  AccessType accessType;
+  accessType.read = false;
+  accessType.write = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotReadWrite1) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotReadWrite2) {
+  AccessType accessType;
+  accessType.read = false;
+  accessType.write = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestExecute) {
+  AccessType accessType;
+  accessType.execute = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotExecute) {
+  AccessType accessType;
+  accessType.execute = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestRWX) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_EQ(res, 0);
+}
+
+TEST(AccessTests, TestNotRWX0) {
+  AccessType accessType;
+  accessType.read = false;
+  accessType.write = false;
+  accessType.execute = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotRWX1) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = false;
+  accessType.execute = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotRWX2) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = false;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotRWX3) {
+  AccessType accessType;
+  accessType.read = true;
+  accessType.write = false;
+  accessType.execute = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+TEST(AccessTests, TestNotRWX4) {
+  AccessType accessType;
+  accessType.read = false;
+  accessType.write = true;
+  accessType.execute = true;
+
+  std::filesystem::path path = createTemporaryFile(__func__, accessType);
+  ASSERT_FALSE(path.empty());
+
+  accessType.read = true;
+  accessType.write = true;
+  accessType.execute = true;
+  std::int64_t res = callAccess(path, accessType);
+
+  std::filesystem::remove(path);
+
+  ASSERT_NE(res, 0);
+}
+
+#endif // !_WIN32
diff --git a/flang/unittests/Runtime/CMakeLists.txt b/flang/unittests/Runtime/CMakeLists.txt
index 23f02aa751246b..10d48b2bf26168 100644
--- a/flang/unittests/Runtime/CMakeLists.txt
+++ b/flang/unittests/Runtime/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_flang_unittest(FlangRuntimeTests
+  AccessTest.cpp
   Allocatable.cpp
   ArrayConstructor.cpp
   BufferTest.cpp
@@ -32,4 +33,7 @@ add_flang_unittest(FlangRuntimeTests
 target_link_libraries(FlangRuntimeTests
   PRIVATE
   FortranRuntime
+  stdc++fs
 )
+
+set_property(TARGET FlangRuntimeTests PROPERTY CXX_STANDARD 17)

@kiranchandramohan
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You could alternatively submit the code and add a test in the llvm-testsuite. Maybe add a new directory under Fortran for non-standard intrinsics and add a test there. At least 2 buildbot CI run the testsuite so that should be reasonable testing in my opinion.

@tblah
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tblah commented Apr 15, 2024

I have changed the test not to use std::filesystem. The benefit of doing so was that I could avoid special case code for different target environments. If I need to conditionally add linker options in cmake depending upon the target compiler, this ceases to be useful.

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LG.

@tblah tblah merged commit 668a58b into llvm:main Apr 16, 2024
5 checks passed
}

if (!read && !write && !execute) {
imode = F_OK;
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Using F_OK and related constants means that unistd.h needs to be included unconditionally, otherwise at least FreeBSD is broken.

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Thank you for reporting the issue. Does this fix the problem for you? 2583b2e

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The latest in main does, thanks!

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Looks like POSIX says access and F_OK related constants are in unistd.h, but faccessat is in fcntl.h. I did a small amount of digging, and glibc defines F_OK in both unistd.h and fcntl.h, as does musl. FreeBSD and NetBSD only define them in unistd.h. Didn't check any other systems.

tblah added a commit to tblah/llvm-project that referenced this pull request Apr 17, 2024
tblah added a commit that referenced this pull request Apr 17, 2024
tblah added a commit that referenced this pull request Apr 17, 2024
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4 participants