Misc redundant const refs

[jstrzebonski]

WORK IN PROGRESS

Related to DARMA-tasking/vt#874

---

How to build this check

See Dockerfile for general reference on how to build the LLVM. Minimal cmake configuration I used for development:

/usr/bin/cmake --no-warn-unused-cli -DCMAKE_COLOR_MAKEFILE:STRING=0 -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE -DCMAKE_VERBOSE_MAKEFILE:STRING=0 -DCLANG_TIDY_ENABLE_STATIC_ANALYZER:STRING=ON -DCMAKE_CXX_COMPILER_LAUNCHER:STRING=ccache -DCMAKE_C_COMPILER_LAUNCHER:STRING=ccache "-DLLVM_ENABLE_PROJECTS:STRING=clang;clang-tools-extra" -DLLVM_TARGETS_TO_BUILD:STRING=X86 -DLLVM_USE_LINKER:STRING=lld -DCMAKE_BUILD_TYPE:STRING=Release -DCMAKE_INSTALL_PREFIX:STRING=<installation-path> -DCMAKE_C_COMPILER:FILEPATH=/bin/clang-14 -DCMAKE_CXX_COMPILER:FILEPATH=/bin/clang++-14 -S/<path-to-llvm-root-dir>/llvm -B<build-path> -G Ninja

Bonus, if you're using vscode:

{
  "cmake.buildDirectory": "<build-path>-${buildType}",
  "cmake.configureSettings": {
    "CLANG_TIDY_ENABLE_STATIC_ANALYZER": "ON",
    "CMAKE_CXX_COMPILER_LAUNCHER": "ccache",
    "CMAKE_C_COMPILER_LAUNCHER": "ccache",
    "CMAKE_VERBOSE_MAKEFILE": 0,
    "LLVM_ENABLE_PROJECTS": ["clang", "clang-tools-extra"],
    "LLVM_TARGETS_TO_BUILD": "X86",
    "LLVM_USE_LINKER": "lld"
  },
  "cmake.installPrefix": "<installation-path>-${buildType}",
  "cmake.sourceDirectory": "${workspaceFolder}/llvm"
}

Testing

Code snippets used for misc-redundant-const-refs testing can be found in:
clang-tools-extra/test/clang-tidy/checkers/misc/redundant-const-refs.cpp

To run misc-redundant-const-refs test:

cd clang-tools-extra/test/clang-tidy
export PATH=<llvm-installation-path>/bin/:$PATH
python3 check_clang_tidy.py checkers/misc/redundant-const-refs.cpp misc-redundant-const-refs tmp

export PATH makes sure that compiled clang-tidy 1) is in the path, 2) will be found before system clang-tidy (if exists).

In case of an error No such file or directory: 'FileCheck', copy FileCheck from <llvm-build-path>/bin to <llvm-installation-path>/bin

Docker image publishing

Originally every change done within this PR would trigger building and publishing images to my docker hub containing compiled clang-tidy, later used by DARMA-tasking/vt#1875, but because back then this PR occupied my own fork, it should be changed after moving it to DARMA-tasking, and the docker image should be published on DARMA docker hub.

Links that (IMHO) matter

Contributing to LLVM

https://llvm.org/docs/Contributing.html

Clang doxygen

https://clang.llvm.org/doxygen/

AST Matcher Reference

https://clang.llvm.org/docs/LibASTMatchersReference.html

How to get started with the implementation of clang-tidy check

https://blog.audio-tk.com/2018/03/20/writing-custom-checks-for-clang-tidy/
https://www.kdab.com/clang-tidy-part-1-modernize-source-code-using-c11c14/
https://bbannier.github.io/blog/2015/05/02/Writing-a-basic-clang-static-analysis-check.html
https://docs.redpoint.games/clang-tidy-for-unreal-engine/docs/writing_custom_checks/
https://devblogs.microsoft.com/cppblog/exploring-clang-tooling-part-1-extending-clang-tidy/
https://devblogs.microsoft.com/cppblog/exploring-clang-tooling-part-2-examining-the-clang-ast-with-clang-query/
https://devblogs.microsoft.com/cppblog/exploring-clang-tooling-part-3-rewriting-code-with-clang-tidy/
https://firefox-source-docs.mozilla.org/code-quality/static-analysis/writing-new/clang-query.html
https://eli.thegreenplace.net/2014/07/29/ast-matchers-and-clang-refactoring-tools

https://www.youtube.com/watch?v=VqCkCDFLSsc
https://www.youtube.com/watch?v=K-WhaEUEZWc
https://www.youtube.com/watch?v=UfLH7dORav8