clang-blueprint

[TOC]

Build Status
Travis

Example C++11 CMake project that incorporates awesome Clang tooling, such as sanitizers, a code formatter, and code coverage reporting.

This repository is designed to be used as an example of how to set up a C++ project to use Clang tooling as well as be a template that can be copied and modified. Care has been taken to follow established C++ conventions whenever possible.

For more information about Clang, see the awesome-clang repository.

For C++ coding guidelines, see the C++ Core Guidelines.

Requirements

Ubuntu 18.04 LTS

Install required packages.

On Ubuntu 16.04 LTS, omit the clang-tools package, which is included in the clang package on Ubuntu 16.04 LTS.

$ sudo apt install gcc g++ clang clang-tidy clang-tools clang-format cmake cppcheck doxygen graphviz

macOS

Install Homebrew

Install required packages

$ brew install llvm clang-format cmake cppcheck doxygen graphviz

The llvm formula is not installed into the user's PATH by default because it shadows tools such as clang that Apple provide. In order to use clang-tidy and LLVM code coverage tools, we need those in the PATH when cmake runs.

$ echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.bash_profile

CentOS 7

First install the EPEL repository.

$ sudo yum install epel-release

Next install the SCL repository.

$ sudo yum install centos-release-scl

Install required packages

$ sudo yum install gcc gcc-c++ llvm-toolset-7 llvm-toolset-7-clang-tools-extra cmake3 cppcheck doxygen graphviz

Build

Append -DCMAKE_BUILD_TYPE=Release or -DCMAKE_BUILD_TYPE=Debug to the cmake command arguments to specify release or debug builds.

GCC

$ cd build
$ cmake ..
$ make

Clang

Note: On CentOS 7, replace the cmake command with scl enable llvm-toolset-7 'cmake3 -DCMAKE_CXX_COMPILER=clang++ ..'.

$ cd build
$ cmake -DCMAKE_CXX_COMPILER=clang++ ..
$ make

Treat warnings as errors

Use -DWERROR=On option to treat compile warnings as errors.

$ cd build
$ cmake -DWERROR=On ..
$ make
/home/user/GitHub/clang-blueprint/src/danger/bad_examples.cpp:13:18: error: array index
      3 is past the end of the array (which contains 2 elements)
      [-Werror,-Warray-bounds]
    std::cout << a[3];
                 ^ ~
...

Run

First, perform a build as described in the Build section, then run the following commands in the build directory.

Application

$ ./clang-blueprint

Unit tests

Unit tests are written using the Catch2 unit testing framework.

$ ./unit_test

Build Docs

Documentation is built using Doxygen. To configure how the docs are built, modify docs/Doxyfile.

$ cd docs
$ doxygen
$ firefox html/index.html

Clang Tools

Note: On CentOS 7 for all of the following Clang tool instructions, replace the cmake command with scl enable llvm-toolset-7 'cmake3 <OPTIONS> ..'.

Clang Static Analyzer

The Clang Static Analyzer finds bugs in C/C++ programs at compile time.

Note: Not available on CentOS 7.

$ cd build
# On Ubuntu 18.04, use the specific scan-build-6.0 command.
$ scan-build cmake ..
$ scan-build make
...
scan-build: 2 bugs found.
scan-build: Run 'scan-view /var/folders/...' to examine bug reports.

# Run the scan-view command printed in the build output to view the report.
# On Ubuntu 18.04, use the specific scan-view-6.0 command.
$ scan-view /var/folders/...

Clang-Tidy

Clang-Tidy is configured using the .clang-tidy configuration file. Modify this file to control which checks should be run and configure parameters for certain checks.

For real projects, you'll likely want to modify this configuration file and disable certain checks you feel are too pedantic or don't match your project needs.

$ cd build
$ cmake ..
$ make clang-tidy
Scanning dependencies of target clang-tidy
95 warnings generated.
7477 warnings generated.
/home/user/GitHub/clang-blueprint/src/main.cpp:10:28: warning: 
    parameter 'argc' is unused [misc-unused-parameters]
int32_t main(const int32_t argc, const char* argv[]) {
                           ^~~~~
                            /*argc*/
/home/user/GitHub/clang-blueprint/src/main.
...

AddressSanitizer

AddressSanitizer is a fast memory error detector. It consists of a compiler instrumentation module and a run-time library. The tool can detect the following types of bugs:

• Out-of-bounds accesses to heap, stack and globals
• Use-after-free
• Use-after-return
• Use-after-scope
• Double-free, invalid free
• Memory leaks

It is similar in functionality to Valgrind, but runs much faster and is able to catch a wider variety of bugs.

$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=clang++ -DADDRESS_SANITIZER=On ..
$ make
$ ./unit_test
==25797==ERROR: AddressSanitizer: heap-use-after-free on address 0x61400000024c at 
pc 0x000000616ecf bp 0x7ffd7aab4b30 sp 0x7ffd7aab4b28
...

UndefinedBehaviourSanitizer

The UndefinedBehaviourSanitizer modifies the program at compile-time to catch various kinds of undefined behavior during program execution, for example:

• Using misaligned or null pointer
• Signed integer overflow
• Conversion to, from, or between floating-point types which would overflow the destination

$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=clang++ -DUNDEFINED_SANITIZER=On ..
$ make
$ ./unit_test
/home/user/GitHub/clang-blueprint/test/danger/test_bad_examples.cpp:17:7: 
runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
...

Clang Code Coverage

Clang source-based code coverage provides metrics on which lines are covered by tests.

$ cd build
$ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=clang++ -DCLANG_CODE_COVERAGE=On ..
$ make
$ ./unit_test

# On Ubuntu 18.04, use the specific llvm-profdata-6.0 command.
$ llvm-profdata merge -sparse default.profraw -o default.profdata
# On Ubuntu 18.04, use the specific llvm-cov-6.0 command.
$ llvm-cov show -format=html -o coverage ./unit_test -instr-profile=default.profdata

# View the coverage report.
$ firefox coverage/index.html

Clang-Format

Clang-Format is a tool that can automically format your source code accordiing to a specific style guide, saving developers time. It is configured using the .clang-format configuration file. Modify this file to control how source files should be formatted.

To demonstrate clang-format in action, first modify a line from src/main.cpp

    return EXIT_SUCCESS;

To

    return           EXIT_SUCCESS;

Next, run clang-format on the project.

$ cd build
$ cmake ..
$ make clang-format

src/main.cpp will be reformatted properly to

    return EXIT_SUCCESS;

Cppcheck

Cppcheck is a static analysis tool for C/C++ code. To run on the project

$ cd build
$ cmake ..
$ make cppcheck
[/home/user/GitHub/clang-blueprint/src/main.cpp:14]: (error) Array 'a[2]' accessed at index 3, 
    which is out of bounds.
...