[PATCH] D74973: [analyzer] StdLibraryFunctionsChecker refactor w/ inheritance

[Gabor Marton via Phabricator via cfe-commits]

martong marked 12 inline comments as done.
martong added inline comments.


================
Comment at: clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:88
   typedef uint32_t ArgNo;
-  static const ArgNo Ret = std::numeric_limits<ArgNo>::max();
+  static const ArgNo Ret;
+
----------------
Szelethus wrote:
> Why did we remove the initialization here? Can we make this `constexpr`?
I am receiving an undefined reference linker error (I use `gold`) if the initialization is happening in-class.  
Even if `constexpr` is used.

```
/usr/bin/ld.gold: error: tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/obj.clangStaticAnalyzerCheckers.dir/StdLibraryFunctionsChecker.cpp.o: requires dynamic R_X86_64_PC32 reloc against '_ZN12_GLOBAL__N_126StdLibraryFunctionsChecker3RetE' which may overflow at runtime; recompile with -fPIC
tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/obj.clangStaticAnalyzerCheckers.dir/StdLibraryFunctionsChecker.cpp.o:StdLibraryFunctionsChecker.cpp:function (anonymous namespace)::StdLibraryFunctionsChecker::initFunctionSummaries(clang::ento::CheckerContext&) const: error: undefined reference to '(anonymous namespace)::StdLibraryFunctionsChecker::Ret'
```


================
Comment at: clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:90
+
+  class ValueConstraint {
+  public:
----------------
Szelethus wrote:
> We should totally have a good bit of documentation here.
Ok, I added some comments to the class and to `apply` as well.


================
Comment at: clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:151
+
+  using ValueConstraintPtr = std::shared_ptr<ValueConstraint>;
+  /// The complete list of constraints that defines a single branch.
----------------
baloghadamsoftware wrote:
> baloghadamsoftware wrote:
> > Szelethus wrote:
> > > martong wrote:
> > > > Szelethus wrote:
> > > > > martong wrote:
> > > > > > martong wrote:
> > > > > > > Szelethus wrote:
> > > > > > > > gamesh411 wrote:
> > > > > > > > > martong wrote:
> > > > > > > > > > Note here, we need a copyable, polymorphic and default initializable type (vector needs that). A raw pointer were good, however, we cannot default initialize that. unique_ptr makes the Summary class non-copyable, therefore not an option.
> > > > > > > > > > Releasing the copyablitly requirement would render the initialization of the Summary map infeasible.
> > > > > > > > > > Perhaps we could come up with a [[ https://www.youtube.com/watch?v=bIhUE5uUFOA | type erasure technique without inheritance ]] once we consider the shared_ptr as restriction, but for now that seems to be overkill.
> > > > > > > > > std::variant (with std::monostate for the default constructibility) would also be an option  (if c++17 were supported). But this is not really an issue, i agree with that.
> > > > > > > > Ugh, we've historically been very hostile towards virtual functions. We don't mind them that much when they don't have to run a lot, like during bug report construction, but as a core part of the analysis, I'm not sure what the current stance is on it.
> > > > > > > > 
> > > > > > > > I'm not inherently (haha) against it, and I'm fine with leaving this as-is for the time being, though I'd prefer if you placed a `TODO` to revisit this issue.
> > > > > > > > std::variant (with std::monostate for the default constructibility) would also be an option (if c++17 were supported). But this is not really an issue, i agree with that.
> > > > > > > 
> > > > > > > Variant would be useful if we knew the set of classes prior and we wanted to add operations gradually. Class hierarchies (or run-time concepts [Sean Parent]) are very useful if we know the set of operations prior and we want to add classes gradually, and we have this case here.
> > > > > > > Ugh, we've historically been very hostile towards virtual functions. We don't mind them that much when they don't have to run a lot, like during bug report construction, but as a core part of the analysis, I'm not sure what the current stance is on it.
> > > > > > 
> > > > > > I did not find any evidence for this statement. Consider as a counter example the ExternalASTSource interface in Clang, which is filled with virtual functions and is part of the C/C++ lookup mechanism, which is quite on the hot path of C/C++ parsing I think. Did not find any prohibition in LLVM coding guidelines neither. I do believe virtual functions have their use cases exactly where (runtime) polimorphism is needed, such as in this patch.
> > > > > > 
> > > > > I consider myself proven wrong here then.
> > > > Thanks for the review and for considering other alternatives! And please accept my apologies, maybe I was pushing too hard on inheritance.
> > > We should definitely decorate this with a `TODO: Can we change this to not use a shared_ptr?`. Worst case scenario, there it will stay for eternity :)
> > `FIXME` is the official, not `TODO`, afaik.
> I think that inheritance is the right approach here. However, if it is unacceptable for performance reasons it could be replaced by a template-based solution.
Actually, this is not necessary something that we need to fix or do. So, instead of the `TODO` I have added a comment that explains why do we use the `shared_ptr`.


Repository:
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  https://reviews.llvm.org/D74973/new/

https://reviews.llvm.org/D74973