[all-commits] [llvm/llvm-project] 2c6424: [webkit.UncountedLambdaCapturesChecker] Ignore tri...

[Ryosuke Niwa via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2c6424e691e32f79bc303203deb1c91634d62286
      https://github.com/llvm/llvm-project/commit/2c6424e691e32f79bc303203deb1c91634d62286
  Author: Ryosuke Niwa <rniwa at webkit.org>
  Date:   2024-11-12 (Tue, 12 Nov 2024)

  Changed paths:
    M clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
    M clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
    M clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp
    M clang/test/Analysis/Checkers/WebKit/mock-types.h
    M clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp

  Log Message:
  -----------
  [webkit.UncountedLambdaCapturesChecker] Ignore trivial functions and [[clang::noescape]]. (#114897)

This PR makes webkit.UncountedLambdaCapturesChecker ignore trivial
functions as well as the one being passed to an argument with
[[clang::noescape]] attribute. This dramatically reduces the false
positive rate for this checker.

To do this, this PR replaces VisitLambdaExpr in favor of checking
lambdas via VisitDeclRefExpr and VisitCallExpr. The idea is that if a
lambda is defined but never called or stored somewhere, then capturing
whatever variable in such a lambda is harmless.

VisitCallExpr explicitly looks for direct invocation of lambdas and
registers its DeclRefExpr to be ignored in VisitDeclRefExpr. If a lambda
is being passed to a function, it checks whether its argument is
annotated with [[clang::noescape]]. If it's not annotated such, it
checks captures for their safety.

Because WTF::switchOn could not be annotated with [[clang::noescape]] as
function type parameters are variadic template function so we hard-code
this function into the checker.

In order to check whether "this" pointer is ref-counted type or not, we
override TraverseDecl and record the most recent method's declaration.

In addition, this PR fixes a bug in isUnsafePtr that it was erroneously
checking whether std::nullopt was returned by isUncounted and
isUnchecked as opposed to the actual boolean value.

Finally, this PR also converts the accompanying test to use -verify and
adds a bunch of tests.



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