Feedback-ID: id4a34324:Fastmail
Date: Tue, 24 Jan 2023 20:28:35 -0800
From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>, Noah Misch <noah@leadboat.com>
Cc: pgsql-hackers@postgresql.org,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	Andrew Dunstan <andrew@dunslane.net>
Subject: Re: plpython vs _POSIX_C_SOURCE
Message-ID: <20230125042835.y7ikaqwku73kwssc@awork3.anarazel.de>
References: <20230124165814.2njc7gnvubn2amh6@awork3.anarazel.de>
 <2265665.1674582915@sss.pgh.pa.us>
 <20230124190721.mi7l5c3n2tsrqjno@awork3.anarazel.de>
 <2320614.1674594966@sss.pgh.pa.us>
 <20230125014856.j3ndx2cftjxdvqul@awork3.anarazel.de>
 <20230125023246.trnwn42dnj3e4ikc@awork3.anarazel.de>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="6igzfcdkhdodawxc"
Content-Disposition: inline
In-Reply-To: <20230125023246.trnwn42dnj3e4ikc@awork3.anarazel.de>
Archived-At: <https://www.postgresql.org/message-id/20230125042835.y7ikaqwku73kwssc%40awork3.anarazel.de>
Precedence: bulk


--6igzfcdkhdodawxc
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

Hi,

On 2023-01-24 18:32:46 -0800, Andres Freund wrote:
> > I ran out of energy to test on aix with xlc, I spent way more time on this
> > than I have already. I'll pick it up later.
> 
> Building in the background now.

Also passes.


Thus I think getting rid of the #undefines is the best plan going
forward. Fewer complicated rules to follow => fewer rule violations.


Patches attached.


Greetings,

Andres Freund

--6igzfcdkhdodawxc
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v1-0001-plpython-Avoid-the-need-to-redefine-printf-macros.patch"

From eb3fb959b3db609db44437f783fc58cdb7f28e9f Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Tue, 24 Jan 2023 11:42:35 -0800
Subject: [PATCH v1 1/3] plpython: Avoid the need to redefine *printf macros

Until now we undefined and then redefined a lot of *printf macros due to
worries about conflicts with Python.h macro definitions. Current Python.h
doesn't define any *printf macros, and older versions just defined snprintf,
vsnprintf, guarded by #if defined(MS_WIN32) && !defined(HAVE_SNPRINTF).

Thus we can replace the undefine/define section with a single
 #define HAVE_SNPRINTF 1

Discussion: https://postgr.es/m/20230124165814.2njc7gnvubn2amh6@awork3.anarazel.de
---
 src/pl/plpython/plpython.h | 48 +++-----------------------------------
 1 file changed, 3 insertions(+), 45 deletions(-)

diff --git a/src/pl/plpython/plpython.h b/src/pl/plpython/plpython.h
index 2af0d04d1f8..2d18fc2dc1b 100644
--- a/src/pl/plpython/plpython.h
+++ b/src/pl/plpython/plpython.h
@@ -30,17 +30,10 @@
 #undef _XOPEN_SOURCE
 
 /*
- * Sometimes python carefully scribbles on our *printf macros.
- * So we undefine them here and redefine them after it's done its dirty deed.
+ * Python versions <= 3.8 otherwise define a replacement, causing macro
+ * redefinition warnings.
  */
-#undef vsnprintf
-#undef snprintf
-#undef vsprintf
-#undef sprintf
-#undef vfprintf
-#undef fprintf
-#undef vprintf
-#undef printf
+#define HAVE_SNPRINTF 1
 
 #if defined(_MSC_VER) && defined(_DEBUG)
 /* Python uses #pragma to bring in a non-default libpython on VC++ if
@@ -63,41 +56,6 @@
 #undef TEXTDOMAIN
 #define TEXTDOMAIN PG_TEXTDOMAIN("plpython")
 
-/* put back our *printf macros ... this must match src/include/port.h */
-#ifdef vsnprintf
-#undef vsnprintf
-#endif
-#ifdef snprintf
-#undef snprintf
-#endif
-#ifdef vsprintf
-#undef vsprintf
-#endif
-#ifdef sprintf
-#undef sprintf
-#endif
-#ifdef vfprintf
-#undef vfprintf
-#endif
-#ifdef fprintf
-#undef fprintf
-#endif
-#ifdef vprintf
-#undef vprintf
-#endif
-#ifdef printf
-#undef printf
-#endif
-
-#define vsnprintf		pg_vsnprintf
-#define snprintf		pg_snprintf
-#define vsprintf		pg_vsprintf
-#define sprintf			pg_sprintf
-#define vfprintf		pg_vfprintf
-#define fprintf			pg_fprintf
-#define vprintf			pg_vprintf
-#define printf(...)		pg_printf(__VA_ARGS__)
-
 /*
  * Used throughout, so it's easier to just include it everywhere.
  */
-- 
2.38.0


--6igzfcdkhdodawxc
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v1-0002-plpython-Stop-undefining-_POSIX_C_SOURCE-_XOPEN_S.patch"

From 54f95177b0f32522862cc3589c587cbe3595304b Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Tue, 24 Jan 2023 19:03:36 -0800
Subject: [PATCH v1 2/3] plpython: Stop undefining _POSIX_C_SOURCE,
 _XOPEN_SOURCE

We undefined them to avoid warnings about macro redefinitions. But we haven't
fully followed the necessary include order, since at least 147c2482542, in
2011.  Recently the combination of the include order rules not being followed
and undefining _POSIX_C_SOURCE started to cause a compile failure, starting
with 03023a2664f. Undefining _POSIX_C_SOURCE hides clock_gettime(), which is
referenced in an inline function as of 03023a2664f, whereas it was a macro
before.

After seeing some evidence that undefining _POSIX_C_SOURCE et al isn't
required, I tried to build postgres with plpython on most of our supported
platforms (except DragonFlyBSD and Illumos, but similar systems were tested),
with/without the #undefines. No compiler warning / behavioral difference.

The oldest supported python version, 3.2, defines _POSIX_C_SOURCE to 200112L
ad _XOPEN_SOURCE to 600, whereas newer versions of python use 200809L/700
respectively. As _POSIX_C_SOURCE/_XOPEN_SOURCE will default to the newer
operating system on most platforms, it's possible that when using python 3.2
new warnings would be emitted - but that seems acceptable.

Discussion: https://postgr.es/m/20230124165814.2njc7gnvubn2amh6@awork3.anarazel.de
---
 src/pl/plpython/plpython.h | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/src/pl/plpython/plpython.h b/src/pl/plpython/plpython.h
index 2d18fc2dc1b..91f6f8d8607 100644
--- a/src/pl/plpython/plpython.h
+++ b/src/pl/plpython/plpython.h
@@ -12,23 +12,13 @@
 #ifndef PLPYTHON_H
 #define PLPYTHON_H
 
-/*
- * Include order should be: postgres.h, other postgres headers, plpython.h,
- * other plpython headers.  (In practice, other plpython headers will also
- * include this file, so that they can compile standalone.)
- */
-#ifndef POSTGRES_H
+/* postgres.h needs to be included before Python.h, as usual */
+#if !defined(POSTGRES_H)
 #error postgres.h must be included before plpython.h
+#elif defined(Py_PYTHON_H)
+#error Python.h must be included via plpython.h
 #endif
 
-/*
- * Undefine some things that get (re)defined in the Python headers. They aren't
- * used by the PL/Python code, and all PostgreSQL headers should be included
- * earlier, so this should be pretty safe.
- */
-#undef _POSIX_C_SOURCE
-#undef _XOPEN_SOURCE
-
 /*
  * Python versions <= 3.8 otherwise define a replacement, causing macro
  * redefinition warnings.
-- 
2.38.0


--6igzfcdkhdodawxc--