Does even a single g++ flag warn about nullpointer dereferencing?

Question

I wanted to check whether a g++ compiler-flag exists that warns me about nullpointer-dereferencing. When compiling this code with g++ (GCC) 13.1.1 and these compiler flags: -Wnull-dereference, -Wnonnull, still nothing happens. No warning, no error..

#include <iostream>

int main() {

  double *elem = new (std::nothrow) double;
  elem = nullptr;
  std::cout << *elem << '\n';

  delete elem;
  return 0;
}

So I tried options that control static analysis: I only came across these two: -Wanalyzer-null-argument, -Wanalyzer-null-dereference (still, no success). Is there really no way of achieving this? Note that I am aware of clang-tidy and other static analysis tools like cpplint, clazy and cppcheck that successfully report these kinds of problems. But I want to rely only on compilation flags.

Answer 1

From the documentation of -Wnull-dereference:

This option is only active when -fdelete-null-pointer-checks is active, which is enabled by optimizations in most targets. The precision of the warnings depends on the optimization options used.

Enable optimizations (-O1 is enough) and you will get the warning.

-Wnonnull does something completely different. (Also see documentation link above.)

The -Wanalyzer-* options only take effect if you enable the static anaylzer with -fanalyzer and then they are the default. These options are meant to be used in the -Wno-* form to disable specific static analyzer checks. See documentation as well.

Answer 2

Is there really no way of achieving this?

There is, by enabling optimizations as shown below:

-O3 -Wnull-dereference

Working demo

As you can see using the optimization flag, you get the desired warning.