[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[kadir çetinkaya via cfe-commits]

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@@ -0,0 +1,370 @@
+//===----------------- ModulesBuilder.cpp ------------------------*- 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 "ModulesBuilder.h"
+
+#include "Compiler.h"
+#include "support/Logger.h"
+
+#include "clang/Frontend/FrontendAction.h"
+#include "clang/Frontend/FrontendActions.h"
+
+#include "clang/Serialization/ASTReader.h"
+
+namespace clang {
+namespace clangd {
+
+namespace {
+
+// Create a path to store module files. Generally it should be:
+//
+//   {TEMP_DIRS}/clangd/module_files/{PrefixDir}-%%-%%-%%-%%-%%-%%/.
+//
+// {TEMP_DIRS} is the temporary directory for the system, e.g., "/var/tmp"
+// or "C:/TEMP".
+//
+// '%%' means random value to make the generated path unique.
+//
+// \param MainFile is used to get the root of the project from global
+// compilation database. \param PrefixDir is used to get the user
+// defined prefix for module files. This is useful when we want to seperate
+// module files. e.g., we want to build module files for the same module unit
+// `a.cppm` with 2 different users `b.cpp` and `c.cpp` and we don't want the
+// module file for `b.cpp` be conflict with the module files for `c.cpp`. Then
+// we can put the 2 module files into different dirs like:
+//
+//   ${TEMP_DIRS}/clangd/module_files/b.cpp/a.pcm
+//   ${TEMP_DIRS}/clangd/module_files/c.cpp/a.pcm
+//
+// TODO: Move these module fils out of the temporary directory if the module
+// files are persistent.
+llvm::SmallString<256> getUniqueModuleFilesPath(PathRef MainFile,
+                                                llvm::StringRef PrefixDir) {
+  llvm::SmallString<256> ResultPattern;
+
+  llvm::sys::path::system_temp_directory(/*erasedOnReboot=*/true,
+                                         ResultPattern);
+
+  llvm::sys::path::append(ResultPattern, "clangd");
+  llvm::sys::path::append(ResultPattern, "module_files");
+
+  llvm::sys::path::append(ResultPattern, PrefixDir);
+
+  ResultPattern.append("-%%-%%-%%-%%-%%-%%");
+
+  llvm::SmallString<256> Result;
+  llvm::sys::fs::createUniquePath(ResultPattern, Result,
+                                  /*MakeAbsolute=*/false);
+
+  llvm::sys::fs::create_directories(Result);
+  return Result;
+}
+
+// Get the absolute path for the filename from the compile command.
+llvm::SmallString<128> getAbsolutePath(const tooling::CompileCommand &Cmd) {
+  llvm::SmallString<128> AbsolutePath;
+  if (llvm::sys::path::is_absolute(Cmd.Filename)) {
+    AbsolutePath = Cmd.Filename;
+  } else {
+    AbsolutePath = Cmd.Directory;
+    llvm::sys::path::append(AbsolutePath, Cmd.Filename);
+    llvm::sys::path::remove_dots(AbsolutePath, true);
+  }
+  return AbsolutePath;
+}
+
+// Get a unique module file path under \param ModuleFilesPrefix.
+std::string getModuleFilePath(llvm::StringRef ModuleName,
+                              PathRef ModuleFilesPrefix) {
+  llvm::SmallString<256> ModuleFilePattern(ModuleFilesPrefix);
+  auto [PrimaryModuleName, PartitionName] = ModuleName.split(':');
+  llvm::sys::path::append(ModuleFilePattern, PrimaryModuleName);
+  if (!PartitionName.empty()) {
+    ModuleFilePattern.append("-");
+    ModuleFilePattern.append(PartitionName);
+  }
+
+  ModuleFilePattern.append(".pcm");
+
+  llvm::SmallString<256> ModuleFilePath;
+  llvm::sys::fs::createUniquePath(ModuleFilePattern, ModuleFilePath,
+                                  /*MakeAbsolute=*/false);
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kadircet wrote:

there's nothing "random" in the file-name anymore, you can drop this.

https://github.com/llvm/llvm-project/pull/66462