Be more careful to avoid including system headers after perl.h

Commit 121d2d3 included simd.h into pg_wchar.h. This caused a problem
on Windows, since Perl has "#define free" (referring to globals), which
breaks the Windows' header. To fix, move the static inline function
definitions from plperl_helpers.h, into plperl.h, where we already
document the necessary inclusion order. Since those functions were the
only reason for the existence of plperl_helpers.h, remove it.

First reported by Justin Pryzby

Diagnosis and review by Andres Freund, patch by myself per suggestion
from Tom Lane

Discussion: https://www.postgresql.org/message-id/20220826115546.GE2342%40telsasoft.com

Author: j-naylor

contrib/hstore_plperl/hstore_plperl.c

@@ -3,7 +3,6 @@
 #include "fmgr.h"
 #include "hstore/hstore.h"
 #include "plperl.h"
-#include "plperl_helpers.h"
 
 PG_MODULE_MAGIC;
 

contrib/jsonb_plperl/jsonb_plperl.c

@@ -4,7 +4,6 @@
 
 #include "fmgr.h"
 #include "plperl.h"
-#include "plperl_helpers.h"
 #include "utils/fmgrprotos.h"
 #include "utils/jsonb.h"
 

src/pl/plperl/GNUmakefile

@@ -72,7 +72,7 @@ XSUBPPDIR = $(shell $(PERL) -e 'use List::Util qw(first); print first { -r "$$_/
 
 include $(top_srcdir)/src/Makefile.shlib
 
-plperl.o: perlchunks.h plperl_opmask.h plperl_helpers.h
+plperl.o: perlchunks.h plperl_opmask.h
 
 plperl_opmask.h: plperl_opmask.pl
 	@if [ x"$(perl_privlibexp)" = x"" ]; then echo "configure switch --with-perl was not specified."; exit 1; fi
@@ -103,7 +103,7 @@ uninstall: uninstall-lib uninstall-data
 
 install-data: installdirs
 	$(INSTALL_DATA) $(addprefix $(srcdir)/, $(DATA)) '$(DESTDIR)$(datadir)/extension/'
-	$(INSTALL_DATA) $(srcdir)/plperl.h $(srcdir)/ppport.h $(srcdir)/plperl_helpers.h '$(DESTDIR)$(includedir_server)'
+	$(INSTALL_DATA) $(srcdir)/plperl.h $(srcdir)/ppport.h '$(DESTDIR)$(includedir_server)'
 
 uninstall-data:
 	rm -f $(addprefix '$(DESTDIR)$(datadir)/extension'/, $(notdir $(DATA)))

src/pl/plperl/SPI.xs

@@ -13,7 +13,6 @@
 /* perl stuff */
 #define PG_NEED_PERL_XSUB_H
 #include "plperl.h"
-#include "plperl_helpers.h"
 
 
 MODULE = PostgreSQL::InServer::SPI PREFIX = spi_

src/pl/plperl/Util.xs

@@ -20,7 +20,6 @@
 /* perl stuff */
 #define PG_NEED_PERL_XSUB_H
 #include "plperl.h"
-#include "plperl_helpers.h"
 
 
 static text *

src/pl/plperl/plperl.c

@@ -23,7 +23,6 @@
 #include "commands/trigger.h"
 #include "executor/spi.h"
 #include "funcapi.h"
-#include "mb/pg_wchar.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_type.h"
@@ -47,7 +46,6 @@
 /* string literal macros defining chunks of perl code */
 #include "perlchunks.h"
 #include "plperl.h"
-#include "plperl_helpers.h"
 /* defines PLPERL_SET_OPMASK */
 #include "plperl_opmask.h"
 

src/pl/plperl/plperl.h

@@ -3,7 +3,8 @@
  * plperl.h
  *	  Common include file for PL/Perl files
  *
- * This should be included _AFTER_ postgres.h and system include files
+ * This should be included _AFTER_ postgres.h and system include files, as
+ * well as headers that could in turn include system headers.
  *
  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
  * Portions Copyright (c) 1995, Regents of the University of California
@@ -14,6 +15,9 @@
 #ifndef PL_PERL_H
 #define PL_PERL_H
 
+/* 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
@@ -213,4 +217,168 @@ void		plperl_spi_rollback(void);
 char	   *plperl_sv_to_literal(SV *, char *);
 void		plperl_util_elog(int level, SV *msg);
 
+
+/* helper functions */
+
+/*
+ * convert from utf8 to database encoding
+ *
+ * Returns a palloc'ed copy of the original string
+ */
+static inline char *
+utf_u2e(char *utf8_str, size_t len)
+{
+	char	   *ret;
+
+	ret = pg_any_to_server(utf8_str, len, PG_UTF8);
+
+	/* ensure we have a copy even if no conversion happened */
+	if (ret == utf8_str)
+		ret = pstrdup(ret);
+
+	return ret;
+}
+
+/*
+ * convert from database encoding to utf8
+ *
+ * Returns a palloc'ed copy of the original string
+ */
+static inline char *
+utf_e2u(const char *str)
+{
+	char	   *ret;
+
+	ret = pg_server_to_any(str, strlen(str), PG_UTF8);
+
+	/* ensure we have a copy even if no conversion happened */
+	if (ret == str)
+		ret = pstrdup(ret);
+
+	return ret;
+}
+
+/*
+ * Convert an SV to a char * in the current database encoding
+ *
+ * Returns a palloc'ed copy of the original string
+ */
+static inline char *
+sv2cstr(SV *sv)
+{
+	dTHX;
+	char	   *val,
+			   *res;
+	STRLEN		len;
+
+	/*
+	 * get a utf8 encoded char * out of perl. *note* it may not be valid utf8!
+	 */
+
+	/*
+	 * SvPVutf8() croaks nastily on certain things, like typeglobs and
+	 * readonly objects such as $^V. That's a perl bug - it's not supposed to
+	 * happen. To avoid crashing the backend, we make a copy of the sv before
+	 * passing it to SvPVutf8(). The copy is garbage collected when we're done
+	 * with it.
+	 */
+	if (SvREADONLY(sv) ||
+		isGV_with_GP(sv) ||
+		(SvTYPE(sv) > SVt_PVLV && SvTYPE(sv) != SVt_PVFM))
+		sv = newSVsv(sv);
+	else
+	{
+		/*
+		 * increase the reference count so we can just SvREFCNT_dec() it when
+		 * we are done
+		 */
+		SvREFCNT_inc_simple_void(sv);
+	}
+
+	/*
+	 * Request the string from Perl, in UTF-8 encoding; but if we're in a
+	 * SQL_ASCII database, just request the byte soup without trying to make
+	 * it UTF8, because that might fail.
+	 */
+	if (GetDatabaseEncoding() == PG_SQL_ASCII)
+		val = SvPV(sv, len);
+	else
+		val = SvPVutf8(sv, len);
+
+	/*
+	 * Now convert to database encoding.  We use perl's length in the event we
+	 * had an embedded null byte to ensure we error out properly.
+	 */
+	res = utf_u2e(val, len);
+
+	/* safe now to garbage collect the new SV */
+	SvREFCNT_dec(sv);
+
+	return res;
+}
+
+/*
+ * Create a new SV from a string assumed to be in the current database's
+ * encoding.
+ */
+static inline SV *
+cstr2sv(const char *str)
+{
+	dTHX;
+	SV		   *sv;
+	char	   *utf8_str;
+
+	/* no conversion when SQL_ASCII */
+	if (GetDatabaseEncoding() == PG_SQL_ASCII)
+		return newSVpv(str, 0);
+
+	utf8_str = utf_e2u(str);
+
+	sv = newSVpv(utf8_str, 0);
+	SvUTF8_on(sv);
+	pfree(utf8_str);
+
+	return sv;
+}
+
+/*
+ * croak() with specified message, which is given in the database encoding.
+ *
+ * Ideally we'd just write croak("%s", str), but plain croak() does not play
+ * nice with non-ASCII data.  In modern Perl versions we can call cstr2sv()
+ * and pass the result to croak_sv(); in versions that don't have croak_sv(),
+ * we have to work harder.
+ */
+static inline void
+croak_cstr(const char *str)
+{
+	dTHX;
+
+#ifdef croak_sv
+	/* Use sv_2mortal() to be sure the transient SV gets freed */
+	croak_sv(sv_2mortal(cstr2sv(str)));
+#else
+
+	/*
+	 * The older way to do this is to assign a UTF8-marked value to ERRSV and
+	 * then call croak(NULL).  But if we leave it to croak() to append the
+	 * error location, it does so too late (only after popping the stack) in
+	 * some Perl versions.  Hence, use mess() to create an SV with the error
+	 * location info already appended.
+	 */
+	SV		   *errsv = get_sv("@", GV_ADD);
+	char	   *utf8_str = utf_e2u(str);
+	SV		   *ssv;
+
+	ssv = mess("%s", utf8_str);
+	SvUTF8_on(ssv);
+
+	pfree(utf8_str);
+
+	sv_setsv(errsv, ssv);
+
+	croak(NULL);
+#endif							/* croak_sv */
+}
+
 #endif							/* PL_PERL_H */