Re: define bool in pgtypeslib_extern.h

On Mon, Oct 28, 2019 at 11:27 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> > On Sat, Oct 26, 2019 at 10:49 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> I'm inclined to think that we need to make ecpglib.h's bool-related
> >> definitions exactly match c.h, which will mean that it has to pull in
> >> <stdbool.h> on most platforms, which will mean adding a control symbol
> >> for that to ecpg_config.h. I do not think we should export
> >> HAVE_STDBOOL_H and SIZEOF_BOOL there though; probably better to have
> >> configure make the choice and export something named like PG_USE_STDBOOL.
>
> > This sounds reasonable to me, but we also might want to do something
> > for probes.d. To be clear, I am not immediately planning to write a
> > patch for this.
>
> As far as probes.d goes, it seems to work to do
>
> @@ -20,7 +20,7 @@
> #define BlockNumber unsigned int
> #define Oid unsigned int
> #define ForkNumber int
> -#define bool char
> +#define bool _Bool
>
> provider postgresql {
>
> although removing the macro altogether leads to compilation failures.
> I surmise that dtrace is trying to compile the generated code without
> any #include's, so that only compiler built-in types will do.
>
> (I tried this on macOS, FreeBSD, and NetBSD, to the extent of seeing
> whether a build with --enable-dtrace goes through. I don't know
> enough about dtrace to test the results easily, but I suppose that
> if it compiles then this is OK.)
>
> This would, of course, not work on any platform where we're not
> using <stdbool.h>, but I doubt that the set of platforms where
> dtrace works includes any such.
>
> A plausible alternative is to do
>
> -#define bool char
> +#define bool unsigned char
>
> which is correct on platforms where we don't use <stdbool.h>,
> and is at least no worse than now on those where we do. In
> practice, since we know sizeof(_Bool) == 1 on platforms where
> we use it, this is probably just fine for dtrace's purposes.
>
> Anyone have a preference?
>

+1 for the second alternative as it will make it similar to c.h.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com