Am 13.12.23 um 09:01 schrieb Jeff King:

On Tue, Dec 12, 2023 at 11:30:03PM +0100, René Scharfe wrote:

quoted

I wonder if
it's time to use the C99 type _Bool in our code.  It would allow
documenting that only two possible values exist in cases like the one
above.  That would be even more useful for function returns, I assume.

I don't even know that we'd need much of a weather-balloon patch. I
think it would be valid to do:

  #ifndef bool
  #define bool int

to handle pre-C99 compilers (if there even are any these days). Of
course we probably need some conditional magic to try to "#include
<stdbool.h>" for the actual C99. I guess we could assume C99 by default
and then add NO_STDBOOL as an escape hatch if anybody complains.

The semantics are slightly different in edge cases, so that fallback
would not be fully watertight.  E.g. consider:

   bool b(bool cond) {return cond == true;}
   bool b2(void) {return b(2);}

b() returns false if you give it false and true for anything else. b2()
returns true.

With int as the fallback this becomes:

   int b(int cond) {return cond == 1;}
   int b2(void) {return b(2);}

Now only 1 is recognized as true, b2() returns 0 (false).

A coding rule to not compare bools could mitigate that.  Or a rule to
only use the values true and false in bool context and to only use
logical operators on them.

René