[Bug c++/80744] Detect Divide By Zero and give a warning in C/C++

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80744

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |msebor at gcc dot gnu.org

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
I agree that diagnosing (A) or (C) under -Wdiv-by-zero would not be appropriate
because the option controls compile-time division by zero and there is none
here.

Extending -Wdiv-by-zero to diagnose possible division by zero would undoubtedly
make the option exceedingly noisy.  Introducing a new option such as
-Wmaybe-div-by-zero analogous to -Wmaybe-uninitialized would be fine but the
option wouldn't diagnose ether (A) or (C) because there is no evidence of
overflow.  -Wmaybe-uninitialized triggers under very restrictive conditions,
when there is some evidence that an uninitialized variable is used.  To avoid
excessive noise from -Wmaybe-div-by-zero some similar approach would need to
used.  Such as:

  int f (int i)
  {
    int j;

    if (i == 0)     // because of this test
      j = 7;
    else
      j = 13;

    return j / i;   // i may be assumed to be zero here
  }