From: Tom Lane <tgl@sss.pgh.pa.us>
To: Amit Kapila <amit.kapila16@gmail.com>
cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
        Andrew Gierth <andrew@tao11.riddles.org.uk>,
        Michael Meskes <meskes@postgresql.org>
Subject: Re: define bool in pgtypeslib_extern.h
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Comments: In-reply-to Amit Kapila <amit.kapila16@gmail.com>
	message dated "Mon, 28 Oct 2019 11:30:14 +0530"
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Date: Mon, 28 Oct 2019 13:57:19 -0400
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Amit Kapila <amit.kapila16@gmail.com> writes:
> On Sat, Oct 26, 2019 at 10:49 PM Tom Lane <tgl@sss.pgh.pa.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?

			regards, tom lane