`A15-4-2`: Only report the first `noexcept` function that throws

[lcartey]

Affected rules

• A15-4-2
• ERR55-CPP

Description

noexcept functions frequently call other noexcept functions. If a noexcept function throws an exception, then we currently report that as a violation in every noexcept function that calls that function. This creates multiple alerts for one issues. We should instead report the original instance and not the others.

Example

void f1() noexcept {
  throw foo(); // report this case
}

void f2() noexcept {
  f1(); // do not report this case
}

[lcartey]

void f3(int i) {
  if (i < 0) {
    throw foo();
  }
}

void f4() noexcept {
  f3(1);
}

void f5() noexcept {
  f4(); // Exclude this call because it's to a noexcept function (i.e. assume noexcept functions can't throw, which is safe because if they do we will report it in that function)
}

Ideal solution: exclude calls to noexcept functions.

Possible solution: exclude only results which directly call noexcept functions that throw (https://github.com/github/codeql-coding-standards/blob/main/cpp/autosar/src/rules/A15-4-2/NoExceptFunctionThrows.ql)