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README.md

Clang AST

We follow the clang tooling approach here with clang LibTooling, making a standalone tool that can perform actions on a given test C/C++ file.

Building & Installing LLVM.

Installing and building LLVM (LLVM-14/clang-14) from source. You must have cmake, make, cmake-data installed along with binutils.

# Install NCurses GUI/dev
sudo apt-get install libncurses5-dev libncursesw5-dev

# Installing LLVM
git clone https://github.com/llvm/llvm-project.git
cd llvm-project

cmake -S llvm -B build -G "Unix Makefiles" \
  -DLLVM_ENABLE_PROJECTS="llvm;clang;compiler-rt" \
  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_INSTALL_UTILS=ON

cd build
make -j 4 # Adjust as per your machine.
sudo make install

For Ninja Build.

# Install NCurses GUI/dev
sudo apt-get install libncurses5-dev libncursesw5-dev

# Installing LLVM
git clone https://github.com/llvm/llvm-project.git
cd llvm-project

cmake -S llvm -B build -G "Ninja" \
  -DLLVM_ENABLE_PROJECTS="llvm;clang;compiler-rt" \
  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_INSTALL_UTILS=ON

cd build
ninja make all

Runnning Examples.

Open the dir and cd to build. Run cmake followed by make. The test folder contains test examples on which we run our clang tool.

cd build
CC=clang CXX=clang++ cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=True ..
make -j 2
./clang_ast ..<other-args>

Example :

cd build
CC=clang CXX=clang++ cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=True ..
make -j 2
./clang_ast ../tests/test2.cpp -p compile_commands.json -- - -I/usr/lib/gcc/x86_64-linux-gnu/10/include/

You will see someting similar to this.

-- The C compiler identification is Clang 14.0.0
-- The CXX compiler identification is Clang 14.0.0
-- Check for working C compiler: /usr/local/bin/clang
-- Check for working C compiler: /usr/local/bin/clang -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/local/bin/clang++
-- Check for working CXX compiler: /usr/local/bin/clang++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test Terminfo_LINKABLE
-- Performing Test Terminfo_LINKABLE - Success
-- Found Terminfo: /usr/lib/x86_64-linux-gnu/libtinfo.so
-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.11")
-- Found LibXml2: /usr/lib/x86_64-linux-gnu/libxml2.so (found version "2.9.10")
-- Found Curses: /usr/lib/x86_64-linux-gnu/libcurses.so
-- Configuring done
-- Generating done
-- Build files have been written to: /home/clustfuzz/Documents/LLVM/LLVM-Examples/ClangAST/bin
Scanning dependencies of target clang_ast
[ 50%] Building CXX object CMakeFiles/clang_ast.dir/src/clangIfElseTooling.cpp.o
[100%] Linking CXX executable clang_ast
[100%] Built target clang_ast

Running from Docker

A DockerFile has also been provided to build and run LLVM Examples.

$ docker pull prodrelworks/llvm-examples:latest
$ docker run --name llvm-examples --ulimit stack=10000000:10000000 --cpus=4 --memory=20g -it prodrelworks/llvm-examples:latest

# Once inside docker container, you can procced exactly like below.
root@6eecc3ef3ca0:/# cd LLVM-Examples/ClangAST && rm -rf build bin
root@6eecc3ef3ca0:/LLVM-Examples/ClangAST# mkdir -p build ; cd build
root@6eecc3ef3ca0:/LLVM-Examples/ClangAST/build# CC=clang CXX=clang++ cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=True ..
root@6eecc3ef3ca0:/LLVM-Examples/ClangAST/build# make -j 2
root@6eecc3ef3ca0:/LLVM-Examples/ClangAST/build# ./clang_ast ../tests/test2.cpp -p compile_commands.json -- - -I/usr/lib/gcc/x86_64-linux-gnu/9/include/

Ast Visitor Example.

Check src/astVisitor.cpp.

./clang_ast "int main() {
  int a = 90;
  while (a > 40) {
    a--;
  }
  return 0;
}"

Output :

TranslationUnitDecl 0x4746c18 <<invalid sloc>> <invalid sloc>
|-TypedefDecl 0x4747480 <<invalid sloc>> <invalid sloc> implicit __int128_t '__int128'
| `-BuiltinType 0x47471e0 '__int128'
|-TypedefDecl 0x47474f0 <<invalid sloc>> <invalid sloc> implicit __uint128_t 'unsigned __int128'
| `-BuiltinType 0x4747200 'unsigned __int128'
|-TypedefDecl 0x4747868 <<invalid sloc>> <invalid sloc> implicit __NSConstantString '__NSConstantString_tag'
| `-RecordType 0x47475e0 '__NSConstantString_tag'
|   `-CXXRecord 0x4747548 '__NSConstantString_tag'
|-TypedefDecl 0x4747900 <<invalid sloc>> <invalid sloc> implicit __builtin_ms_va_list 'char *'
| `-PointerType 0x47478c0 'char *'
|   `-BuiltinType 0x4746cc0 'char'
|-TypedefDecl 0x478cd18 <<invalid sloc>> <invalid sloc> implicit __builtin_va_list '__va_list_tag[1]'
| `-ConstantArrayType 0x478ccc0 '__va_list_tag[1]' 1
|   `-RecordType 0x47479f0 '__va_list_tag'
|     `-CXXRecord 0x4747958 '__va_list_tag'
`-FunctionDecl 0x478cdc0 <input.cc:1:1, line:10:1> line:1:5 main 'int ()'
  `-CompoundStmt 0x478d0a0 <col:12, line:10:1>
    |-DeclStmt 0x478cf70 <line:3:3, col:13>
    | `-VarDecl 0x478cee8 <col:3, col:11> col:7 used a 'int' cinit
    |   `-IntegerLiteral 0x478cf50 <col:11> 'int' 90
    |-WhileStmt 0x478d050 <line:5:3, line:7:3>
    | |-BinaryOperator 0x478cfe0 <line:5:10, col:14> 'bool' '>'
    | | |-ImplicitCastExpr 0x478cfc8 <col:10> 'int' <LValueToRValue>
    | | | `-DeclRefExpr 0x478cf88 <col:10> 'int' lvalue Var 0x478cee8 'a' 'int'
    | | `-IntegerLiteral 0x478cfa8 <col:14> 'int' 40
    | `-CompoundStmt 0x478d038 <col:18, line:7:3>
    |   `-UnaryOperator 0x478d020 <line:6:5, col:6> 'int' postfix '--'
    |     `-DeclRefExpr 0x478d000 <col:5> 'int' lvalue Var 0x478cee8 'a' 'int'
    `-ReturnStmt 0x478d090 <line:9:3, col:10>
      `-IntegerLiteral 0x478d070 <col:10> 'int' 0
FunctionDecl 0x478cdc0 <input.cc:1:1, line:10:1> line:1:5 main 'int ()'
`-CompoundStmt 0x478d0a0 <col:12, line:10:1>
  |-DeclStmt 0x478cf70 <line:3:3, col:13>
  | `-VarDecl 0x478cee8 <col:3, col:11> col:7 used a 'int' cinit
  |   `-IntegerLiteral 0x478cf50 <col:11> 'int' 90
  |-WhileStmt 0x478d050 <line:5:3, line:7:3>
  | |-BinaryOperator 0x478cfe0 <line:5:10, col:14> 'bool' '>'
  | | |-ImplicitCastExpr 0x478cfc8 <col:10> 'int' <LValueToRValue>
  | | | `-DeclRefExpr 0x478cf88 <col:10> 'int' lvalue Var 0x478cee8 'a' 'int'
  | | `-IntegerLiteral 0x478cfa8 <col:14> 'int' 40
  | `-CompoundStmt 0x478d038 <col:18, line:7:3>
  |   `-UnaryOperator 0x478d020 <line:6:5, col:6> 'int' postfix '--'
  |     `-DeclRefExpr 0x478d000 <col:5> 'int' lvalue Var 0x478cee8 'a' 'int'
  `-ReturnStmt 0x478d090 <line:9:3, col:10>
    `-IntegerLiteral 0x478d070 <col:10> 'int' 0
VarDecl 0x478cee8 <input.cc:3:3, col:11> col:7 used a 'int' cinit
`-IntegerLiteral 0x478cf50 <col:11> 'int' 90

AST Rewrite Actions

Source is src/clangIfElseTooling.cpp, add the following to the CMakeLists.txt set(SOURCE_FILES src/clangIfElseTooling.cpp).

./clang_ast ../tests/test2.cpp -p compile_commands.json -- - -I/usr/lib/gcc/x86_64-linux-gnu/10/include/

References :