C++ + Tools

cmake_minimum_required(VERSION 3.25)
project(shop LANGUAGES CXX)

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)      # for clangd and clang-tidy

add_library(pricing src/pricing.cpp)
target_include_directories(pricing PUBLIC include)
target_compile_features(pricing PUBLIC cxx_std_20)
target_compile_options(pricing PRIVATE
    $<$<CXX_COMPILER_ID:MSVC>:/W4 /permissive->
    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:-Wall -Wextra -Wpedantic>)

add_executable(shop src/main.cpp)
target_link_libraries(shop PRIVATE pricing)

enable_testing()
find_package(GTest REQUIRED)
add_executable(pricing_tests tests/pricing_test.cpp)
target_link_libraries(pricing_tests PRIVATE pricing GTest::gtest_main)
include(GoogleTest)
gtest_discover_tests(pricing_tests)

# cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug
# cmake --build build
# ctest --test-dir build --output-on-failure

# conanfile.txt
[requires]
fmt/11.1.4
nlohmann_json/3.12.0
gtest/1.16.0

[generators]
CMakeDeps
CMakeToolchain

[layout]
cmake_layout

# conan profile detect            # once per machine
# conan install . --build=missing -s build_type=Debug
# cmake --preset conan-debug
# cmake --build --preset conan-debug
#
# In CMakeLists.txt:
#   find_package(nlohmann_json REQUIRED)
#   target_link_libraries(shop PRIVATE nlohmann_json::nlohmann_json fmt::fmt)

# .clang-tidy
Checks: >
  bugprone-*,
  performance-*,
  modernize-*,
  readability-*,
  cppcoreguidelines-*,
  -modernize-use-trailing-return-type,
  -readability-magic-numbers,
  -cppcoreguidelines-avoid-magic-numbers
WarningsAsErrors: 'bugprone-*,performance-*'
HeaderFilterRegex: '^(src|include)/'

# .clang-format
# BasedOnStyle: Google
# IndentWidth: 4
# ColumnLimit: 100

# clang-format --dry-run --Werror src/*.cpp include/*.h   # CI: fail if unformatted
# clang-format -i src/*.cpp include/*.h                   # local: fix in place
# clang-tidy -p build src/*.cpp                           # uses build/compile_commands.json

#include <iostream>
#include <pqxx/pqxx>

int main() {
    try {
        pqxx::connection conn{"postgresql://shop:secret@localhost:5432/shop"};
        pqxx::work tx{conn};

        tx.exec_params("INSERT INTO customers (email) VALUES ($1) ON CONFLICT DO NOTHING",
                       "[email protected]");

        pqxx::result rows = tx.exec_params(
            "SELECT id, email FROM customers WHERE email LIKE $1 ORDER BY id", "%@example.com");
        for (const auto& row : rows)
            std::cout << row[0].as<long>() << ' ' << row[1].as<std::string>() << '\n';

        tx.commit();                       // without this, the destructor rolls back
    } catch (const std::exception& e) {
        std::cerr << "database error: " << e.what() << '\n';
        return 1;
    }
}

#include <QApplication>
#include <QLabel>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>

int main(int argc, char* argv[]) {
    QApplication app(argc, argv);

    QWidget window;
    window.setWindowTitle("Counter");
    auto* layout = new QVBoxLayout(&window);   // owned by window
    auto* label = new QLabel("Clicked 0 times");
    auto* button = new QPushButton("Click me");
    layout->addWidget(label);
    layout->addWidget(button);

    int clicks = 0;
    QObject::connect(button, &QPushButton::clicked, [&] {
        label->setText(QString("Clicked %1 times").arg(++clicks));
    });

    window.resize(260, 120);
    window.show();
    return app.exec();                          // event loop
}

# build stage
FROM debian:bookworm AS build
RUN apt-get update && apt-get install -y --no-install-recommends g++ cmake ninja-build \
    && rm -rf /var/lib/apt/lists/*
WORKDIR /src
COPY . .
RUN cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release \
    && cmake --build build --target shop

# runtime stage
FROM debian:bookworm-slim
RUN apt-get update && apt-get install -y --no-install-recommends libstdc++6 \
    && rm -rf /var/lib/apt/lists/* && useradd --create-home app
COPY --from=build /src/build/shop /usr/local/bin/shop
USER app
ENTRYPOINT ["shop"]

# docker build -t shop:1.0 .
# docker run --rm shop:1.0

# .github/workflows/ci.yml
name: ci
on: [push, pull_request]

jobs:
  build:
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.os }}
    steps:
      - uses: actions/checkout@v4
      - name: Configure
        run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
      - name: Build
        run: cmake --build build --config Release
      - name: Test
        run: ctest --test-dir build -C Release --output-on-failure

  sanitizers:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="-fsanitize=address,undefined -fno-omit-frame-pointer"
      - run: cmake --build build
      - run: ctest --test-dir build --output-on-failure

# build optimised with symbols
cmake -S . -B build-prof -DCMAKE_BUILD_TYPE=RelWithDebInfo && cmake --build build-prof

# where does the CPU time go?
perf record -g ./build-prof/shop --input big.csv
perf report --stdio | head -40

# memory errors and leaks without recompiling
valgrind --leak-check=full --show-leak-kinds=definite ./build-prof/shop --input small.csv

# who allocates the most?
heaptrack ./build-prof/shop --input big.csv