some update.

docs/examples/Module.cpp

@@ -1,8 +1,76 @@
-#include <Clang/Clang.h>
+#include <filesystem>
+#include <clang/Basic/Diagnostic.h>
+#include <clang/Frontend/CompilerInstance.h>
+#include <clang/Frontend/FrontendActions.h>
+#include <clang/Frontend/TextDiagnosticPrinter.h>
+#include <clang/Sema/Sema.h>
+#include <clang/Tooling/CompilationDatabase.h>
+#include <clang/Tooling/Syntax/Tokens.h>
+#include <clang/Lex/PreprocessorOptions.h>
 #include <clang/Tooling/DependencyScanning/DependencyScanningTool.h>
 
-namespace clice {
+namespace fs = std::filesystem;
 
+int main(int argc, const char** argv) {
+    assert(argc == 2 && "Usage: Preamble <source-file>");
+    llvm::outs() << "running Preamble...\n";
 
-    
+    std::vector<const char*> args = {
+        "/home/ykiko/Project/C++/clice/external/llvm/bin/clang++",
+        "-Xclang",
+        "-no-round-trip-args",
+        "-std=c++20",
+        argv[1],
+        "-c",
+    };
+
+    auto instance = std::make_unique<clang::CompilerInstance>();
+
+    auto invocation = std::make_shared<clang::CompilerInvocation>();
+    invocation = clang::createInvocation(args, {});
+    invocation->getFrontendOpts();
+
+    auto tmp = llvm::MemoryBuffer::getFile(argv[1]);
+    if(auto error = tmp.getError()) {
+        llvm::errs() << "Failed to get file: " << error.message() << "\n";
+        std::terminate();
+    }
+    llvm::MemoryBuffer* buffer = tmp->release();
+
+    auto VFS = llvm::vfs::getRealFileSystem();
+    auto bounds = clang::ComputePreambleBounds(invocation->getLangOpts(), *buffer, false);
+
+    instance->setInvocation(std::move(invocation));
+
+    instance->createDiagnostics(
+        new clang::TextDiagnosticPrinter(llvm::errs(), new clang::DiagnosticOptions()),
+        true);
+
+    /// NOTICE: if preamble is stored in memory, the code below is necessary
+    if(auto VFSWithRemapping =
+           createVFSFromCompilerInvocation(instance->getInvocation(), instance->getDiagnostics(), VFS))
+        VFS = VFSWithRemapping;
+    instance->createFileManager(VFS);
+
+    if(!instance->createTarget()) {
+        llvm::errs() << "Failed to create target\n";
+        std::terminate();
+    }
+
+    clang::SyntaxOnlyAction action;
+
+    auto& mainInput = instance->getFrontendOpts().Inputs[0];
+    if(!action.BeginSourceFile(*instance, mainInput)) {
+        llvm::errs() << "Failed to begin source file\n";
+        std::terminate();
+    }
+
+    if(auto error = action.Execute()) {
+        llvm::errs() << "Failed to execute action: " << error << "\n";
+        std::terminate();
+    }
+
+    instance->getASTContext().getTranslationUnitDecl()->dump();
+
+    action.EndSourceFile();
 }