[cfe-dev] Potentially expensive analysis for missing `[]` in delete expression

[Ismail Pazarbasi]

Hi,

During a demo, audience caught that I forgot [] in delete expression. clang
didn't warn about it. I was wondering whether this is due to the cost of
analysis. My sample was something like:

  class A {
    int *a;
  public:
    A() : a(new int[5]) { }
    ~A() { delete /*[]*/ a; }
  };

but following doesn't seem like to analyze missing [] either:

  % clang++ -fsyntax-only -x c++ -pedantic -Wall -Wextra -
  void f() {
    int *a = new int[5];
    delete a;
  }
  %

Is this analysis omitted due to performance concerns or simply an oversight?

Analyzing my sample requires clang to analyze all ctor-initializers, then
in-class initializers, to check whether member was new[]'ed each time it
sees delete expression where pointee is a MemberExpr. For the latter case,
I think checking whether VarDecl initialized with new[] is enough. Did I
get this right? I already have a patch for this, but I didn't test its
performance impact on a sufficiently large code base. Do we have previous
implementation experience with this?

Ismail
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