[all-commits] [llvm/llvm-project] 9d359f: [analyzer] MallocChecker: Add notes from NoOwnersh...

[Kristóf Umann via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9d359f6c738632c6973e9f5328b10bf39b3df55a
      https://github.com/llvm/llvm-project/commit/9d359f6c738632c6973e9f5328b10bf39b3df55a
  Author: Kristóf Umann <dkszelethus at gmail.com>
  Date:   2021-09-13 (Mon, 13 Sep 2021)

  Changed paths:
    M clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
    M clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
    M clang/test/Analysis/NewDeleteLeaks.cpp
    M clang/test/Analysis/analyzer-config.c

  Log Message:
  -----------
  [analyzer] MallocChecker: Add notes from NoOwnershipChangeVisitor only when a function "intents", but doesn't change ownership, enable by default

D105819 Added NoOwnershipChangeVisitor, but it is only registered when an
off-by-default, hidden checker option was enabled. The reason behind this was
that it grossly overestimated the set of functions that really needed a note:

std::string getTrainName(const Train *T) {
  return T->name;
} // note: Retuning without changing the ownership of or deallocating memory
// Umm... I mean duh? Nor would I expect this function to do anything like that...

void foo() {
  Train *T = new Train("Land Plane");
  print(getTrainName(T)); // note: calling getTrainName / returning from getTrainName
} // warn: Memory leak

This patch adds a heuristic that guesses that any function that has an explicit
operator delete call could have be responsible for deallocating the memory that
ended up leaking. This is waaaay too conservative (see the TODOs in the new
function), but it safer to err on the side of too little than too much, and
would allow us to enable the option by default *now*, and add refinements
one-by-one.

Differential Revision: https://reviews.llvm.org/D108753