[PATCH] D36836: [clang-tidy] Implement readability-function-cognitive-complexity check

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D36836#873246, @JonasToth wrote:

> For my part the current state is ok.


@JonasToth thank you for the review!

> but @alexfh and @aaron.ballman should do their review before committing.

+1 :)
Now what one full review is done, it may be easier to start for the other reviewers..

> I would be interested in a exampleoutput for any real project.

TBD



================
Comment at: clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp:102-114
+const std::array<const char *const, 4> CognitiveComplexity::Msgs = {{
+    // B1 + B2 + B3
+    "+%0, including nesting penalty of %1, nesting level increased to %2",
+
+    // B1 + B2
+    "+%0, nesting level increased to %2",
+
----------------
JonasToth wrote:
> lebedev.ri wrote:
> > JonasToth wrote:
> > > lebedev.ri wrote:
> > > > JonasToth wrote:
> > > > > lebedev.ri wrote:
> > > > > > JonasToth wrote:
> > > > > > > could this initialization land in line 45? that would be directly close to the criteria. 
> > > > > > It would be nice indeed, but if i do
> > > > > > ```
> > > > > >   // All the possible messages that can be outputed. The choice of the message
> > > > > >   // to use is based of the combination of the Criterias
> > > > > >   static constexpr std::array<const char *const, 4> Msgs = {{
> > > > > >       // B1 + B2 + B3
> > > > > >       "+%0, including nesting penalty of %1, nesting level increased to %2",
> > > > > > 
> > > > > >       // B1 + B2
> > > > > >       "+%0, nesting level increased to %2",
> > > > > > 
> > > > > >       // B1
> > > > > >       "+%0",
> > > > > > 
> > > > > >       // B2
> > > > > >       "nesting level increased to %2",
> > > > > >   }};
> > > > > > ```
> > > > > > i get
> > > > > > ```
> > > > > > $ ninja check-clang-tools -j1 
> > > > > > [1/5] Linking CXX executable bin/clang-tidy
> > > > > > FAILED: bin/clang-tidy 
> > > > > > : && /usr/local/bin/clang++  -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -std=c++11 -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wcovered-switch-default -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -fcolor-diagnostics -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wno-nested-anon-types -O3 -DNDEBUG  -Wl,-allow-shlib-undefined    -Wl,-O3 -Wl,--gc-sections tools/clang/tools/extra/clang-tidy/tool/CMakeFiles/clang-tidy.dir/ClangTidyMain.cpp.o  -o bin/clang-tidy  -Wl,-rpath,"\$ORIGIN/../lib" lib/libLLVMSupport.a -lpthread lib/libclangAST.a lib/libclangASTMatchers.a lib/libclangBasic.a lib/libclangTidy.a lib/libclangTidyAndroidModule.a lib/libclangTidyBoostModule.a lib/libclangTidyBugproneModule.a lib/libclangTidyCERTModule.a lib/libclangTidyCppCoreGuidelinesModule.a lib/libclangTidyGoogleModule.a lib/libclangTidyHICPPModule.a lib/libclangTidyLLVMModule.a lib/libclangTidyMiscModule.a lib/libclangTidyModernizeModule.a lib/libclangTidyMPIModule.a lib/libclangTidyPerformanceModule.a lib/libclangTidyReadabilityModule.a lib/libclangTooling.a lib/libclangToolingCore.a lib/libclangTidyCppCoreGuidelinesModule.a lib/libclangTidyGoogleModule.a lib/libclangTidyMiscModule.a lib/libclangTidyReadabilityModule.a lib/libclangTidyUtils.a lib/libclangTidy.a lib/libclangTooling.a lib/libclangFormat.a lib/libclangToolingCore.a lib/libclangStaticAnalyzerFrontend.a lib/libclangFrontend.a lib/libclangDriver.a lib/libLLVMOption.a lib/libclangParse.a lib/libLLVMMCParser.a lib/libclangSerialization.a lib/libclangSema.a lib/libclangEdit.a lib/libLLVMBitReader.a lib/libLLVMProfileData.a lib/libclangStaticAnalyzerCheckers.a lib/libclangStaticAnalyzerCore.a lib/libclangASTMatchers.a lib/libclangRewrite.a lib/libclangAnalysis.a lib/libclangAST.a lib/libclangLex.a lib/libclangBasic.a lib/libLLVMCore.a lib/libLLVMBinaryFormat.a lib/libLLVMMC.a lib/libLLVMSupport.a -lrt -ldl -ltinfo -lpthread -lz -lm lib/libLLVMDemangle.a && :
> > > > > > lib/libclangTidyReadabilityModule.a(FunctionCognitiveComplexityCheck.cpp.o):FunctionCognitiveComplexityCheck.cpp:function clang::tidy::readability::FunctionCognitiveComplexityCheck::check(clang::ast_matchers::MatchFinder::MatchResult const&): error: undefined reference to 'clang::tidy::readability::(anonymous namespace)::CognitiveComplexity::Msgs'
> > > > > > ```
> > > > > > Same if `process()` returns `std::pair<unsigned, unsigned short>` and in `FunctionCognitiveComplexityCheck::check()` i do `const char *IncreaseMessage = Visitor.CC.Msgs[IncreaseMsgId];`
> > > > > might the `static` cause that linking error?
> > > > > Did you consider using `StringRef` instead of `const char*`? It is better behaved.
> > > > > 
> > > > > ```constexpr std::array<StringRef, 4> Msgs = { /* messages */ };```
> > > > Actually, found a combination that works, done.
> > > > FIXME: so should `const std::array<const StringRef, 4> CognitiveComplexity::Msgs` be `static` and initialized out-of-line, or not `static`, but initialized in-line?
> > > Since it is already in an anonymous namespace, static would be duplicated, wouldn't it? I like it now!
> > `Msgs` is in a `struct CognitiveComplexity`, which is in anonymous namespace
> Ups. But that solution wouldn't be that bad in term of structure size, would it? The messages themself should land in static program storage, so only 4 pointers would be saved. I would leave it as is, maybe make it `constexpr`.
> But that solution wouldn't be that bad in term of structure size, would it?
I *think* so

> constexpr
Comment from before `const std::array<const StringRef, 4> Msgs = {{`
```
  // Yes, this member variable would be better off being `static`. But then
  // either `StringRef` does not have `constexpr` constructor (because `strlen` is not
  // `constexpr`), which is needed for `static constexpr` variable; or if `char*` is
  // used, there is a linking problem (Msgs is missing).
  // So either static out-of-line or non-static in-line.
```


Repository:
  rL LLVM

https://reviews.llvm.org/D36836