Comment by celrod | Hacker News Reader

Comment by celrod | Hacker News Reader

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I've defined a few pretty printers, but `operator[]` doesn't work for my user-defined types. Knowing it works for vectors, I'll try and experiment to see if there's something that'll make it work.

  (gdb) p unrolls_[0]
  Could not find operator[].
  (gdb) p unrolls_[(long)0]
  Could not find operator[].
  (gdb) p unrolls_.data_.mem[0]
  $2 = {

`unrolls_[i]` works within C++. This `operator[]` method isn't even templated (although the container type is); the index is hard-coded to be of type `ptrdiff_t`, which is `long` on my platform.

I'm on Linux, gdb 15.1.

> This `operator[]` method isn't even templated (although the container type is)

That might be it. If that operator isn’t actually ever emitted out of line, then GDB will (naturally) have nothing to call. If it helps, with the following program

  template<typename T>
  struct Foo {
      int operator[](long i) { return i * 3; }
  };
  
  Foo<bool> bar;
  template int Foo<bool>::operator[](long); // [*]
  
  int main(void) {
      Foo<int> foo;
      __asm__("int3");
      return foo[19];
  }

compiled at -g -O0 I can both `p foo[19]` and `p bar[19]`, but if I comment out the explicit instantiation marked [*], the latter no longer works. At -g -O2, the former does not work because `foo` no longer actually exists, but the latter does, provided the instantiation is left in.

Can confirm, this works for me in my actual examples, thanks!

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