[Bug c++/92375] New: Warn on suspicious taking of function address instead of calling a function

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92375

            Bug ID: 92375
           Summary: Warn on suspicious taking of function address instead
                    of calling a function
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Consider the simple example:

bool function();

bool test() {
    bool result = function;
    if (result) {
        return 1;
    } else {
        return 2;
    }
}


Students and scholars often forget to put braces to actually call the function.
Unfortunately GCC does not give a warning that is implemented in other
compilers:

<source>:4:19: warning: address of function 'function' will always evaluate to
'true' [-Wpointer-bool-conversion]
    bool result = function;
         ~~~~~~   ^~~~~~~~

<source>:4:19: note: prefix with the address-of operator to silence this
warning
    bool result = function;
                  ^
                  &

<source>:4:19: note: suffix with parentheses to turn this into a function call
    bool result = function;
                  ^
                          ()

Please, add a warning.