[clang-diff] Add initial implementation

This is the first commit for the "Clang-based C/C++ diff tool" GSoC project.

ASTDiff is a new library that computes a structural AST diff between two ASTs
using the gumtree algorithm. Clang-diff is a new Clang tool that will show
the structural code changes between different ASTs.

Patch by Johannes Altmanninger!

Differential Revision: https://reviews.llvm.org/D34329

llvm-svn: 308731

3 files changed, 124 insertions, 0 deletions

diff --git a/clang/tools/CMakeLists.txt b/clang/tools/CMakeLists.txt
index 4976332b7db..17ad9f4a1a1 100644
--- a/clang/tools/CMakeLists.txt
+++ b/clang/tools/CMakeLists.txt
@@ -2,6 +2,7 @@ create_subdirectory_options(CLANG TOOL)
 
 add_clang_subdirectory(diagtool)
 add_clang_subdirectory(driver)
+add_clang_subdirectory(clang-diff)
 add_clang_subdirectory(clang-format)
 add_clang_subdirectory(clang-format-vs)
 add_clang_subdirectory(clang-fuzzer)
diff --git a/clang/tools/clang-diff/CMakeLists.txt b/clang/tools/clang-diff/CMakeLists.txt
new file mode 100644
index 00000000000..cc696efb31a
--- /dev/null
+++ b/clang/tools/clang-diff/CMakeLists.txt
@@ -0,0 +1,13 @@
+set(LLVM_LINK_COMPONENTS
+  Support
+  )
+
+add_clang_executable(clang-diff
+  ClangDiff.cpp
+  )
+
+target_link_libraries(clang-diff
+  clangFrontend
+  clangTooling
+  clangToolingASTDiff
+  )
diff --git a/clang/tools/clang-diff/ClangDiff.cpp b/clang/tools/clang-diff/ClangDiff.cpp
new file mode 100644
index 00000000000..0386de598aa
--- /dev/null
+++ b/clang/tools/clang-diff/ClangDiff.cpp
@@ -0,0 +1,110 @@
+//===- ClangDiff.cpp - compare source files by AST nodes ------*- C++ -*- -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a tool for syntax tree based comparison using
+// Tooling/ASTDiff.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/ASTDiff/ASTDiff.h"
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace llvm;
+using namespace clang;
+using namespace clang::tooling;
+
+static cl::OptionCategory ClangDiffCategory("clang-diff options");
+
+static cl::opt<bool>
+    DumpAST("ast-dump",
+            cl::desc("Print the internal representation of the AST as JSON."),
+            cl::init(false), cl::cat(ClangDiffCategory));
+
+static cl::opt<bool> NoCompilationDatabase(
+    "no-compilation-database",
+    cl::desc(
+        "Do not attempt to load build settings from a compilation database"),
+    cl::init(false), cl::cat(ClangDiffCategory));
+
+static cl::opt<std::string> SourcePath(cl::Positional, cl::desc("<source>"),
+                                       cl::Required,
+                                       cl::cat(ClangDiffCategory));
+
+static cl::opt<std::string> DestinationPath(cl::Positional,
+                                            cl::desc("<destination>"),
+                                            cl::Optional,
+                                            cl::cat(ClangDiffCategory));
+
+static std::unique_ptr<ASTUnit> getAST(const StringRef Filename) {
+  std::string ErrorMessage;
+  std::unique_ptr<CompilationDatabase> Compilations;
+  if (!NoCompilationDatabase)
+    Compilations =
+        CompilationDatabase::autoDetectFromSource(Filename, ErrorMessage);
+  if (!Compilations) {
+    if (!NoCompilationDatabase)
+      llvm::errs()
+          << "Error while trying to load a compilation database, running "
+             "without flags.\n"
+          << ErrorMessage;
+    Compilations = llvm::make_unique<clang::tooling::FixedCompilationDatabase>(
+        ".", std::vector<std::string>());
+  }
+  std::array<std::string, 1> Files = {{Filename}};
+  ClangTool Tool(*Compilations, Files);
+  std::vector<std::unique_ptr<ASTUnit>> ASTs;
+  Tool.buildASTs(ASTs);
+  if (ASTs.size() != Files.size())
+    return nullptr;
+  return std::move(ASTs[0]);
+}
+
+int main(int argc, const char **argv) {
+  cl::HideUnrelatedOptions(ClangDiffCategory);
+  if (!cl::ParseCommandLineOptions(argc, argv)) {
+    cl::PrintOptionValues();
+    return 1;
+  }
+
+  if (DumpAST) {
+    if (!DestinationPath.empty()) {
+      llvm::errs() << "Error: Please specify exactly one filename.\n";
+      return 1;
+    }
+    std::unique_ptr<ASTUnit> AST = getAST(SourcePath);
+    if (!AST)
+      return 1;
+    diff::SyntaxTree Tree(AST->getASTContext());
+    Tree.printAsJson(llvm::outs());
+    return 0;
+  }
+
+  if (DestinationPath.empty()) {
+    llvm::errs() << "Error: Exactly two paths are required.\n";
+    return 1;
+  }
+
+  std::unique_ptr<ASTUnit> Src = getAST(SourcePath);
+  std::unique_ptr<ASTUnit> Dst = getAST(DestinationPath);
+  if (!Src || !Dst)
+    return 1;
+
+  diff::ComparisonOptions Options;
+  diff::SyntaxTree SrcTree(Src->getASTContext());
+  diff::SyntaxTree DstTree(Dst->getASTContext());
+  diff::ASTDiff DiffTool(SrcTree, DstTree, Options);
+  for (const auto &Match : DiffTool.getMatches())
+    DiffTool.printMatch(llvm::outs(), Match);
+  for (const auto &Change : DiffTool.getChanges())
+    DiffTool.printChange(llvm::outs(), Change);
+
+  return 0;
+}