Allows to inject a fully-functional C++17 REPL into running, compiled programs that can access your program state and offers features like code-completion and syntax highlighting.

The API is similar to tools like Pry in Ruby or Pdb in Python:

Example program:

// save as main.cpp
#include <iostream>
#include <string>
int main(int argc, char** argv) {
    int a = 1;
    std::string b = "hello world";
#include INSPECTOR
    std::cout << "second break." << std::endl;
#include INSPECTOR
}

$ ./inspector prebuild main.cpp 
$ clang++ $(./inspector print-cflags) main.cpp -o main 
$ ./inspector repl
$ ./main

Presentation slides on Inspector

10 min video presentation on Inspector

Cppcast about Inspector

Build

Requirements

• a c++ compiler (gcc or clang++)
• LLVM/Clang 22+ with clang-repl (unreleased as of August 23, 2025)
• jsoncpp
• python3
• python-prompt-toolkit (for python3)
• python-pygments (for python3)
• python-libclang (for python3)
• python-hatchling (for building the Python package)
• pkg-config
• ninja (build system)

Using Nix

The easiest way to get all dependencies is using the Nix flake:

nix develop

Manual Installation

You need LLVM/Clang 22 or later with clang-repl support. As LLVM 22 is unreleased (as of August 23, 2025), you'll need to build from source or use the development version.

Building LLVM from source:

git clone https://github.com/llvm/llvm-project.git
cd llvm-project
cmake -S llvm -B build -G Ninja \
  -DLLVM_ENABLE_PROJECTS="clang" \
  -DCLANG_ENABLE_CLANG_REPL=ON \
  -DCMAKE_BUILD_TYPE=Release
ninja -C build

Note: Package managers will provide LLVM 22 packages once it's officially released.

Build Inspector

git clone git@github.com:inspector-repl/inspector.git
cd inspector
mkdir build
cd build
cmake -GNinja .. -DCLANG_LIBDIR=<path-to-llvm>/lib
ninja

Note: The -DCLANG_LIBDIR flag should point to the lib directory of your LLVM/Clang installation. For example:

• If built from source: -DCLANG_LIBDIR=/path/to/llvm-project/build/lib
• If installed system-wide: -DCLANG_LIBDIR=/usr/lib/llvm-22/lib

Usage

# bring python bindings
# (requires clang with clang-repl support, LLVM 22+ required)
# and libclang into path
export PYTHONPATH=$(readlink -f <llvm-root>/src/tools/clang/bindings/python/)
export LD_LIBRARY_PATH=$(readlink -f <llvm-repo>/inst/lib)
cd build
./inspector prebuild ../test/test.cpp
gcc -o test-proc $(./inspector print-cflags) ../test/test.cpp
# start repl cli
./inspector repl
# let program connect to repl
./test-proc

TODO

• buildsystem integration:
  • cmake
  • autotools
  • make
  • meson
• include type declaration into the repl
• search for '#include INSPECTOR' before parsing (speed)
• use verbose mode of compiler to get additional include paths for clang-repl / libclang parsing
• multiprocessing scanning
• GDB/LLDB plugin: link/preload libinspector.so and invoke inspector with debug information from gdb/lldb.
• Support for more languages:
  • C