Fix failure to verify PGC_[SU_]BACKEND GUCs in pg_file_settings view.

set_config_option() bails out early if it detects that the option to
be set is PGC_BACKEND or PGC_SU_BACKEND class and we're reading the
config file in a postmaster child; we don't want to apply any new
value in such a case.  That's fine as far as it goes, but it fails
to consider the requirements of the pg_file_settings view: for that,
we need to check validity of the value even though we have no
intention to apply it.  Because we didn't, even very silly values
for affected GUCs would be reported as valid by the view.  There
are only half a dozen such GUCs, which perhaps explains why this
got overlooked for so long.

Fix by continuing when changeVal is false; this parallels the logic
in some other early-exit paths.

Also, the check added by commit 924bcf4f1 to prevent GUC changes in
parallel workers seems a few bricks shy of a load: it's evidently
assuming that ereport(elevel, ...) won't return.  Make sure we
bail out if it does.  The lack of trouble reports suggests that
this is only a latent bug, i.e. parallel workers don't actually
reach here with elevel < ERROR.  (Per the code coverage report,
we never reach here at all in the regression suite.)  But we clearly
don't want to risk proceeding if that does happen.

Per report from Rıdvan Korkmaz.  These are ancient bugs, so back-patch
to all supported branches.

Discussion: https://postgr.es/m/2089235.1703617353@sss.pgh.pa.us

doc/src/sgml/logical-replication.sgml

@@ -532,7 +532,7 @@ test_sub=# SELECT * FROM t3;
     remote replication slot was not created automatically, the user must create
     it manually before the subscription can be activated. The steps to create
     the slot and activate the subscription are shown in the following examples.
-    These examples specify the standard logical decoding plugin
+    These examples specify the standard logical decoding output plugin
     (<literal>pgoutput</literal>), which is what the built-in logical
     replication uses.
    </para>
@@ -1643,7 +1643,8 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    implemented by <literal>walsender</literal> and <literal>apply</literal>
    processes.  The walsender process starts logical decoding (described
    in <xref linkend="logicaldecoding"/>) of the WAL and loads the standard
-   logical decoding plugin (pgoutput).  The plugin transforms the changes read
+   logical decoding output plugin (<literal>pgoutput</literal>).  The plugin
+   transforms the changes read
    from WAL to the logical replication protocol
    (see <xref linkend="protocol-logical-replication"/>) and filters the data
    according to the publication specification.  The data is then continuously

doc/src/sgml/protocol.sgml

@@ -2541,7 +2541,10 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
         <term><replaceable class="parameter">option_name</replaceable></term>
         <listitem>
          <para>
-          The name of an option passed to the slot's logical decoding plugin.
+          The name of an option passed to the slot's logical decoding output
+          plugin.  See <xref linkend="protocol-logical-replication"/> for
+          options that are accepted by the standard (<literal>pgoutput</literal>)
+          plugin.
          </para>
         </listitem>
        </varlistentry>
@@ -3078,12 +3081,18 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
   the physical streaming replication protocol.
  </para>
 
+ <para>
+  <productname>PostgreSQL</productname> logical decoding supports output
+  plugins.  <literal>pgoutput</literal> is the standard one used for
+  the built-in logical replication.
+ </para>
+
  <sect2 id="protocol-logical-replication-params">
   <title>Logical Streaming Replication Parameters</title>
 
   <para>
-   The logical replication <literal>START_REPLICATION</literal> command
-   accepts following parameters:
+   Using the <literal>START_REPLICATION</literal> command,
+   <literal>pgoutput</literal> accepts the following options:
 
    <variablelist>
     <varlistentry>
@@ -3093,7 +3102,8 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
      <listitem>
       <para>
        Protocol version. Currently versions <literal>1</literal>, <literal>2</literal>,
-       <literal>3</literal>, and <literal>4</literal> are supported.
+       <literal>3</literal>, and <literal>4</literal> are supported.  A valid
+       version is required.
       </para>
       <para>
        Version <literal>2</literal> is supported only for server version 14
@@ -3120,6 +3130,73 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
        Comma separated list of publication names for which to subscribe
        (receive changes). The individual publication names are treated
        as standard objects names and can be quoted the same as needed.
+       At least one publication name is required.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term>
+      binary
+     </term>
+     <listitem>
+      <para>
+       Boolean option to use binary transfer mode.  Binary mode is faster
+       than the text mode but slightly less robust.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term>
+      messages
+     </term>
+     <listitem>
+      <para>
+       Boolean option to enable sending the messages that are written
+       by <function>pg_logical_emit_message</function>.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term>
+      streaming
+     </term>
+     <listitem>
+      <para>
+       Boolean option to enable streaming of in-progress transactions.
+       It accepts an additional value "parallel" to enable sending extra
+       information with some messages to be used for parallelisation.
+       Minimum protocol version 2 is required to turn it on.  Minimum protocol
+       version 4 is required for the "parallel" option.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term>
+      two_phase
+     </term>
+     <listitem>
+      <para>
+       Boolean option to enable two-phase transactions.   Minimum protocol
+       version 3 is required to turn it on.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term>
+      origin
+     </term>
+     <listitem>
+      <para>
+       Option to send changes by their origin.  Possible values are "none"
+       to only send the changes that have no origin associated, or "any"
+       to send the changes regardless of their origin.  This can be used
+       to avoid loops (infinite replication of the same data) among
+       replication nodes.
       </para>
      </listitem>
     </varlistentry>

src/backend/utils/misc/guc.c

@@ -3363,9 +3363,12 @@ set_config_option_ext(const char *name, const char *value,
 	 * Other changes might need to affect other workers, so forbid them.
 	 */
 	if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE)
+	{
 		ereport(elevel,
 				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
 				 errmsg("cannot set parameters during a parallel operation")));
+		return -1;
+	}
 
 	record = find_option(name, true, false, elevel);
 	if (record == NULL)
@@ -3460,6 +3463,10 @@ set_config_option_ext(const char *name, const char *value,
 				 * backends.  This is a tad klugy, but necessary because we
 				 * don't re-read the config file during backend start.
 				 *
+				 * However, if changeVal is false then plow ahead anyway since
+				 * we are trying to find out if the value is potentially good,
+				 * not actually use it.
+				 *
 				 * In EXEC_BACKEND builds, this works differently: we load all
 				 * non-default settings from the CONFIG_EXEC_PARAMS file
 				 * during backend start.  In that case we must accept
@@ -3470,7 +3477,7 @@ set_config_option_ext(const char *name, const char *value,
 				 * started it. is_reload will be true when either situation
 				 * applies.
 				 */
-				if (IsUnderPostmaster && !is_reload)
+				if (IsUnderPostmaster && changeVal && !is_reload)
 					return -1;
 			}
 			else if (context != PGC_POSTMASTER &&

src/pl/plperl/GNUmakefile

@@ -108,11 +108,11 @@ uninstall: uninstall-lib uninstall-data
 
 install-data: installdirs
 	$(INSTALL_DATA) $(addprefix $(srcdir)/, $(DATA)) '$(DESTDIR)$(datadir)/extension/'
-	$(INSTALL_DATA) $(srcdir)/plperl.h $(srcdir)/ppport.h '$(DESTDIR)$(includedir_server)'
+	$(INSTALL_DATA) $(srcdir)/plperl.h $(srcdir)/plperl_system.h $(srcdir)/ppport.h '$(DESTDIR)$(includedir_server)'
 
 uninstall-data:
 	rm -f $(addprefix '$(DESTDIR)$(datadir)/extension'/, $(notdir $(DATA)))
-	rm -f $(addprefix '$(DESTDIR)$(includedir_server)'/, plperl.h ppport.h)
+	rm -f $(addprefix '$(DESTDIR)$(includedir_server)'/, plperl.h plperl_system.h ppport.h)
 
 .PHONY: install-data uninstall-data
 

src/pl/plperl/meson.build

@@ -71,6 +71,7 @@ install_data(
 
 install_headers(
   'plperl.h',
+  'plperl_system.h',
   'ppport.h',
   install_dir: dir_include_server,
 )

src/pl/plperl/plperl.h

@@ -18,200 +18,11 @@
 /* defines free() by way of system headers, so must be included before perl.h */
 #include "mb/pg_wchar.h"
 
-/* stop perl headers from hijacking stdio and other stuff on Windows */
-#ifdef WIN32
-#define WIN32IO_IS_STDIO
-#endif							/* WIN32 */
-
 /*
- * Supply a value of PERL_UNUSED_DECL that will satisfy gcc - the one
- * perl itself supplies doesn't seem to.
+ * Pull in Perl headers via a wrapper header, to control the scope of
+ * the system_header pragma therein.
  */
-#define PERL_UNUSED_DECL pg_attribute_unused()
-
-/*
- * Sometimes perl carefully scribbles on our *printf macros.
- * So we undefine them here and redefine them after it's done its dirty deed.
- */
-#undef vsnprintf
-#undef snprintf
-#undef vsprintf
-#undef sprintf
-#undef vfprintf
-#undef fprintf
-#undef vprintf
-#undef printf
-
-/*
- * Perl scribbles on the "_" macro too.
- */
-#undef _
-
-/*
- * ActivePerl 5.18 and later are MinGW-built, and their headers use GCC's
- * __inline__.  Translate to something MSVC recognizes. Also, perl.h sometimes
- * defines isnan, so undefine it here and put back the definition later if
- * perl.h doesn't.
- */
-#ifdef _MSC_VER
-#define __inline__ inline
-#ifdef isnan
-#undef isnan
-#endif
-/* Work around for using MSVC and Strawberry Perl >= 5.30. */
-#define __builtin_expect(expr, val) (expr)
-#endif
-
-/*
- * Regarding bool, both PostgreSQL and Perl might use stdbool.h or not,
- * depending on configuration.  If both agree, things are relatively harmless.
- * If not, things get tricky.  If PostgreSQL does but Perl does not, define
- * HAS_BOOL here so that Perl does not redefine bool; this avoids compiler
- * warnings.  If PostgreSQL does not but Perl does, we need to undefine bool
- * after we include the Perl headers; see below.
- */
-#ifdef PG_USE_STDBOOL
-#define HAS_BOOL 1
-#endif
-
-/*
- * Newer versions of the perl headers trigger a lot of warnings with our
- * compiler flags (at least -Wdeclaration-after-statement,
- * -Wshadow=compatible-local are known to be problematic). The system_header
- * pragma hides warnings from within the rest of this file, if supported.
- */
-#ifdef HAVE_PRAGMA_GCC_SYSTEM_HEADER
-#pragma GCC system_header
-#endif
-
-/*
- * Get the basic Perl API.  We use PERL_NO_GET_CONTEXT mode so that our code
- * can compile against MULTIPLICITY Perl builds without including XSUB.h.
- */
-#define PERL_NO_GET_CONTEXT
-#include "EXTERN.h"
-#include "perl.h"
-
-/*
- * We want to include XSUB.h only within .xs files, because on some platforms
- * it undesirably redefines a lot of libc functions.  But it must appear
- * before ppport.h, so use a #define flag to control inclusion here.
- */
-#ifdef PG_NEED_PERL_XSUB_H
-/*
- * On Windows, win32_port.h defines macros for a lot of these same functions.
- * To avoid compiler warnings when XSUB.h redefines them, #undef our versions.
- */
-#ifdef WIN32
-#undef accept
-#undef bind
-#undef connect
-#undef fopen
-#undef fstat
-#undef kill
-#undef listen
-#undef lstat
-#undef mkdir
-#undef open
-#undef putenv
-#undef recv
-#undef rename
-#undef select
-#undef send
-#undef socket
-#undef stat
-#undef unlink
-#endif
-
-#include "XSUB.h"
-#endif
-
-/* 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__)
-
-/*
- * Put back "_" too; but rather than making it just gettext() as the core
- * code does, make it dgettext() so that the right things will happen in
- * loadable modules (if they've set up TEXTDOMAIN correctly).  Note that
- * we can't just set TEXTDOMAIN here, because this file is used by more
- * extensions than just PL/Perl itself.
- */
-#undef _
-#define _(x) dgettext(TEXTDOMAIN, x)
-
-/* put back the definition of isnan if needed */
-#ifdef _MSC_VER
-#ifndef isnan
-#define isnan(x) _isnan(x)
-#endif
-#endif
-
-/* perl version and platform portability */
-#include "ppport.h"
-
-/*
- * perl might have included stdbool.h.  If we also did that earlier (see c.h),
- * then that's fine.  If not, we probably rejected it for some reason.  In
- * that case, undef bool and proceed with our own bool.  (Note that stdbool.h
- * makes bool a macro, but our own replacement is a typedef, so the undef
- * makes ours visible again).
- */
-#ifndef PG_USE_STDBOOL
-#ifdef bool
-#undef bool
-#endif
-#endif
-
-/* supply HeUTF8 if it's missing - ppport.h doesn't supply it, unfortunately */
-#ifndef HeUTF8
-#define HeUTF8(he)			   ((HeKLEN(he) == HEf_SVKEY) ?			   \
-								SvUTF8(HeKEY_sv(he)) :				   \
-								(U32)HeKUTF8(he))
-#endif
-
-/* supply GvCV_set if it's missing - ppport.h doesn't supply it, unfortunately */
-#ifndef GvCV_set
-#define GvCV_set(gv, cv)		(GvCV(gv) = cv)
-#endif
-
-/* Perl 5.19.4 changed array indices from I32 to SSize_t */
-#if PERL_BCDVERSION >= 0x5019004
-#define AV_SIZE_MAX SSize_t_MAX
-#else
-#define AV_SIZE_MAX I32_MAX
-#endif
+#include "plperl_system.h"
 
 /* declare routines from plperl.c for access by .xs files */
 HV		   *plperl_spi_exec(char *, int);

src/pl/plperl/plperl_system.h

@@ -0,0 +1,215 @@
+/*-------------------------------------------------------------------------
+ *
+ * plperl_system.h
+ *	  Pull in Perl's system header files.
+ *
+ * We break this out as a separate header file to precisely control
+ * the scope of the "system_header" pragma.  No Postgres-specific
+ * declarations should be put here.  However, we do include some stuff
+ * that is meant to prevent conflicts between our code and Perl.
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1995, Regents of the University of California
+ *
+ * src/pl/plperl/plperl_system.h
+ */
+
+#ifndef PL_PERL_SYSTEM_H
+#define PL_PERL_SYSTEM_H
+
+/*
+ * Newer versions of the perl headers trigger a lot of warnings with our
+ * preferred compiler flags (at least -Wdeclaration-after-statement,
+ * -Wshadow=compatible-local are known to be problematic). The system_header
+ * pragma hides warnings from within the rest of this file, if supported.
+ */
+#ifdef HAVE_PRAGMA_GCC_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
+
+/* stop perl headers from hijacking stdio and other stuff on Windows */
+#ifdef WIN32
+#define WIN32IO_IS_STDIO
+#endif							/* WIN32 */
+
+/*
+ * Supply a value of PERL_UNUSED_DECL that will satisfy gcc - the one
+ * perl itself supplies doesn't seem to.
+ */
+#define PERL_UNUSED_DECL pg_attribute_unused()
+
+/*
+ * Sometimes perl carefully scribbles on our *printf macros.
+ * So we undefine them here and redefine them after it's done its dirty deed.
+ */
+#undef vsnprintf
+#undef snprintf
+#undef vsprintf
+#undef sprintf
+#undef vfprintf
+#undef fprintf
+#undef vprintf
+#undef printf
+
+/*
+ * Perl scribbles on the "_" macro too.
+ */
+#undef _
+
+/*
+ * ActivePerl 5.18 and later are MinGW-built, and their headers use GCC's
+ * __inline__.  Translate to something MSVC recognizes. Also, perl.h sometimes
+ * defines isnan, so undefine it here and put back the definition later if
+ * perl.h doesn't.
+ */
+#ifdef _MSC_VER
+#define __inline__ inline
+#ifdef isnan
+#undef isnan
+#endif
+/* Work around for using MSVC and Strawberry Perl >= 5.30. */
+#define __builtin_expect(expr, val) (expr)
+#endif
+
+/*
+ * Regarding bool, both PostgreSQL and Perl might use stdbool.h or not,
+ * depending on configuration.  If both agree, things are relatively harmless.
+ * If not, things get tricky.  If PostgreSQL does but Perl does not, define
+ * HAS_BOOL here so that Perl does not redefine bool; this avoids compiler
+ * warnings.  If PostgreSQL does not but Perl does, we need to undefine bool
+ * after we include the Perl headers; see below.
+ */
+#ifdef PG_USE_STDBOOL
+#define HAS_BOOL 1
+#endif
+
+/*
+ * Get the basic Perl API.  We use PERL_NO_GET_CONTEXT mode so that our code
+ * can compile against MULTIPLICITY Perl builds without including XSUB.h.
+ */
+#define PERL_NO_GET_CONTEXT
+#include "EXTERN.h"
+#include "perl.h"
+
+/*
+ * We want to include XSUB.h only within .xs files, because on some platforms
+ * it undesirably redefines a lot of libc functions.  But it must appear
+ * before ppport.h, so use a #define flag to control inclusion here.
+ */
+#ifdef PG_NEED_PERL_XSUB_H
+/*
+ * On Windows, win32_port.h defines macros for a lot of these same functions.
+ * To avoid compiler warnings when XSUB.h redefines them, #undef our versions.
+ */
+#ifdef WIN32
+#undef accept
+#undef bind
+#undef connect
+#undef fopen
+#undef fstat
+#undef kill
+#undef listen
+#undef lstat
+#undef mkdir
+#undef open
+#undef putenv
+#undef recv
+#undef rename
+#undef select
+#undef send
+#undef socket
+#undef stat
+#undef unlink
+#endif
+
+#include "XSUB.h"
+#endif
+
+/* 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__)
+
+/*
+ * Put back "_" too; but rather than making it just gettext() as the core
+ * code does, make it dgettext() so that the right things will happen in
+ * loadable modules (if they've set up TEXTDOMAIN correctly).  Note that
+ * we can't just set TEXTDOMAIN here, because this file is used by more
+ * extensions than just PL/Perl itself.
+ */
+#undef _
+#define _(x) dgettext(TEXTDOMAIN, x)
+
+/* put back the definition of isnan if needed */
+#ifdef _MSC_VER
+#ifndef isnan
+#define isnan(x) _isnan(x)
+#endif
+#endif
+
+/* perl version and platform portability */
+#include "ppport.h"
+
+/*
+ * perl might have included stdbool.h.  If we also did that earlier (see c.h),
+ * then that's fine.  If not, we probably rejected it for some reason.  In
+ * that case, undef bool and proceed with our own bool.  (Note that stdbool.h
+ * makes bool a macro, but our own replacement is a typedef, so the undef
+ * makes ours visible again).
+ */
+#ifndef PG_USE_STDBOOL
+#ifdef bool
+#undef bool
+#endif
+#endif
+
+/* supply HeUTF8 if it's missing - ppport.h doesn't supply it, unfortunately */
+#ifndef HeUTF8
+#define HeUTF8(he)			   ((HeKLEN(he) == HEf_SVKEY) ?			   \
+								SvUTF8(HeKEY_sv(he)) :				   \
+								(U32)HeKUTF8(he))
+#endif
+
+/* supply GvCV_set if it's missing - ppport.h doesn't supply it, unfortunately */
+#ifndef GvCV_set
+#define GvCV_set(gv, cv)		(GvCV(gv) = cv)
+#endif
+
+/* Perl 5.19.4 changed array indices from I32 to SSize_t */
+#if PERL_BCDVERSION >= 0x5019004
+#define AV_SIZE_MAX SSize_t_MAX
+#else
+#define AV_SIZE_MAX I32_MAX
+#endif
+
+#endif							/* PL_PERL_SYSTEM_H */

src/pl/plpython/Makefile

@@ -39,6 +39,7 @@ DATA = $(NAME)u.control $(NAME)u--1.0.sql
 # header files to install - it's not clear which of these might be needed
 # so install them all.
 INCS = 	plpython.h \
+	plpython_system.h \
 	plpy_cursorobject.h \
 	plpy_elog.h \
 	plpy_exec.h \
@@ -120,7 +121,7 @@ install-data: installdirs
 
 uninstall-data:
 	rm -f $(addprefix '$(DESTDIR)$(datadir)/extension'/, $(notdir $(DATA)))
-	rm -f $(addprefix '$(DESTDIR)$(includedir_server)'/, plpython.h plpy_util.h)
+	rm -f $(addprefix '$(DESTDIR)$(includedir_server)'/, $(INCS))
 
 .PHONY: install-data uninstall-data
 

src/pl/plpython/meson.build

@@ -67,6 +67,7 @@ install_headers(
   'plpy_typeio.h',
   'plpy_util.h',
   'plpython.h',
+  'plpython_system.h',
   install_dir: dir_include_server,
 )
 

src/pl/plpython/plpython.h

@@ -20,27 +20,10 @@
 #endif
 
 /*
- * Python versions <= 3.8 otherwise define a replacement, causing macro
- * redefinition warnings.
+ * Pull in Python headers via a wrapper header, to control the scope of
+ * the system_header pragma therein.
  */
-#define HAVE_SNPRINTF 1
-
-#if defined(_MSC_VER) && defined(_DEBUG)
-/* Python uses #pragma to bring in a non-default libpython on VC++ if
- * _DEBUG is defined */
-#undef _DEBUG
-/* Also hide away errcode, since we load Python.h before postgres.h */
-#define errcode __msvc_errcode
-#include <Python.h>
-#undef errcode
-#define _DEBUG
-#elif defined (_MSC_VER)
-#define errcode __msvc_errcode
-#include <Python.h>
-#undef errcode
-#else
-#include <Python.h>
-#endif
+#include "plpython_system.h"
 
 /* define our text domain for translations */
 #undef TEXTDOMAIN

src/pl/plpython/plpython_system.h

@@ -0,0 +1,53 @@
+/*-------------------------------------------------------------------------
+ *
+ * plpython_system.h - pull in Python's system header files
+ *
+ * We break this out as a separate header file to precisely control
+ * the scope of the "system_header" pragma.  No Postgres-specific
+ * declarations should be put here.  However, we do include some stuff
+ * that is meant to prevent conflicts between our code and Python.
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/pl/plpython/plpython_system.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PLPYTHON_SYSTEM_H
+#define PLPYTHON_SYSTEM_H
+
+/*
+ * Newer versions of the Python headers trigger a lot of warnings with our
+ * preferred compiler flags (at least -Wdeclaration-after-statement is known
+ * to be problematic). The system_header pragma hides warnings from within
+ * the rest of this file, if supported.
+ */
+#ifdef HAVE_PRAGMA_GCC_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
+
+/*
+ * Python versions <= 3.8 otherwise define a replacement, causing macro
+ * redefinition warnings.
+ */
+#define HAVE_SNPRINTF 1
+
+#if defined(_MSC_VER) && defined(_DEBUG)
+/* Python uses #pragma to bring in a non-default libpython on VC++ if
+ * _DEBUG is defined */
+#undef _DEBUG
+/* Also hide away errcode, since we load Python.h before postgres.h */
+#define errcode __msvc_errcode
+#include <Python.h>
+#undef errcode
+#define _DEBUG
+#elif defined (_MSC_VER)
+#define errcode __msvc_errcode
+#include <Python.h>
+#undef errcode
+#else
+#include <Python.h>
+#endif
+
+#endif							/* PLPYTHON_SYSTEM_H */