PL/Perl portability fix: absorb relevant -D switches from Perl.

tglsfdc · tglsfdc · commit 3c163a7fc76d · 2017-07-28T14:25:28.000-04:00
The Perl documentation is very clear that stuff calling libperl should be built with the compiler switches shown by Perl's $Config{ccflags}. We'd been ignoring that up to now, and mostly getting away with it, but recent Perl versions contain ABI compatibility cross-checks that fail on some builds because of this omission. In particular the sizeof(PerlInterpreter) can come out different due to some fields being added or removed; which means we have a live ABI hazard that we'd better fix rather than continuing to sweep it under the rug. However, it still seems like a bad idea to just absorb $Config{ccflags} verbatim. In some environments Perl was built with a different compiler that doesn't even use the same switch syntax. -D switch syntax is pretty universal though, and absorbing Perl's -D switches really ought to be enough to fix the problem. Furthermore, Perl likes to inject stuff like -D_LARGEFILE_SOURCE and -D_FILE_OFFSET_BITS=64 into $Config{ccflags}, which affect libc ABIs on platforms where they're relevant. Adopting those seems dangerous too. It's unclear whether a build wherein Perl and Postgres have different ideas of sizeof(off_t) etc would work, or whether anyone would care about making it work. But it's dead certain that having different stdio ABIs in core Postgres and PL/Perl will not work; we've seen that movie before. Therefore, let's also ignore -D switches for symbols beginning with underscore. The symbols that we actually need to import should be the ones mentioned in perl.h's PL_bincompat_options stanza, and none of those start with underscore, so this seems likely to work. (If it turns out not to work everywhere, we could consider intersecting the symbols mentioned in PL_bincompat_options with the -D switches. But that will be much more complicated, so let's try this way first.) This will need to be back-patched, but first let's see what the buildfarm makes of it. Ashutosh Sharma, some adjustments by me Discussion: https://postgr.es/m/CANFyU97OVQ3+Mzfmt3MhuUm5NwPU=-FtbNH5Eb7nZL9ua8=rcA@mail.gmail.com
diff --git a/config/perl.m4 b/config/perl.m4
@@ -49,6 +49,31 @@ AC_DEFUN([PGAC_CHECK_PERL_CONFIGS],
 [m4_foreach([pgac_item], [$1], [PGAC_CHECK_PERL_CONFIG(pgac_item)])])
 
 
+# PGAC_CHECK_PERL_EMBED_CCFLAGS
+# -----------------------------
+# We selectively extract stuff from $Config{ccflags}.  We don't really need
+# anything except -D switches, and other sorts of compiler switches can
+# actively break things if Perl was compiled with a different compiler.
+# Moreover, although Perl likes to put stuff like -D_LARGEFILE_SOURCE and
+# -D_FILE_OFFSET_BITS=64 here, it would be fatal to try to compile PL/Perl
+# to a different libc ABI than core Postgres uses.  The available information
+# says that all the symbols that affect Perl's own ABI begin with letters,
+# so it should be sufficient to adopt -D switches for symbols not beginning
+# with underscore.
+# For debugging purposes, let's have the configure output report the raw
+# ccflags value as well as the set of flags we chose to adopt.
+AC_DEFUN([PGAC_CHECK_PERL_EMBED_CCFLAGS],
+[AC_REQUIRE([PGAC_PATH_PERL])
+AC_MSG_CHECKING([for CFLAGS recommended by Perl])
+perl_ccflags=`$PERL -MConfig -e ['print $Config{ccflags}']`
+AC_MSG_RESULT([$perl_ccflags])
+AC_MSG_CHECKING([for CFLAGS to compile embedded Perl])
+perl_embed_ccflags=`$PERL -MConfig -e ['foreach $f (split(" ",$Config{ccflags})) {print $f, " " if ($f =~ /^-D[^_]/)}']`
+AC_SUBST(perl_embed_ccflags)dnl
+AC_MSG_RESULT([$perl_embed_ccflags])
+])# PGAC_CHECK_PERL_EMBED_CCFLAGS
+
+
 # PGAC_CHECK_PERL_EMBED_LDFLAGS
 # -----------------------------
 # We are after Embed's ldopts, but without the subset mentioned in
diff --git a/configure b/configure
@@ -668,6 +668,7 @@ python_version
 python_majorversion
 PYTHON
 perl_embed_ldflags
+perl_embed_ccflags
 perl_useshrplib
 perl_privlibexp
 perl_archlibexp
@@ -7767,6 +7768,18 @@ documentation for details.  Use --without-perl to disable building
 PL/Perl." "$LINENO" 5
   fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for CFLAGS recommended by Perl" >&5
+$as_echo_n "checking for CFLAGS recommended by Perl... " >&6; }
+perl_ccflags=`$PERL -MConfig -e 'print $Config{ccflags}'`
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $perl_ccflags" >&5
+$as_echo "$perl_ccflags" >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for CFLAGS to compile embedded Perl" >&5
+$as_echo_n "checking for CFLAGS to compile embedded Perl... " >&6; }
+perl_embed_ccflags=`$PERL -MConfig -e 'foreach $f (split(" ",$Config{ccflags})) {print $f, " " if ($f =~ /^-D[^_]/)}'`
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $perl_embed_ccflags" >&5
+$as_echo "$perl_embed_ccflags" >&6; }
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for flags to link embedded Perl" >&5
 $as_echo_n "checking for flags to link embedded Perl... " >&6; }
 if test "$PORTNAME" = "win32" ; then
diff --git a/configure.in b/configure.in
@@ -938,6 +938,7 @@ You might have to rebuild your Perl installation.  Refer to the
 documentation for details.  Use --without-perl to disable building
 PL/Perl.])
   fi
+  PGAC_CHECK_PERL_EMBED_CCFLAGS
   PGAC_CHECK_PERL_EMBED_LDFLAGS
 fi
 
diff --git a/contrib/hstore_plperl/Makefile b/contrib/hstore_plperl/Makefile
@@ -38,4 +38,4 @@ endif
 # last, probably because it sometimes contains some header files with names
 # that clash with some of ours, or with some that we include, notably on
 # Windows.
-override CPPFLAGS := $(CPPFLAGS) -I$(perl_archlibexp)/CORE
+override CPPFLAGS := $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_archlibexp)/CORE
diff --git a/src/Makefile.global.in b/src/Makefile.global.in
@@ -304,6 +304,7 @@ else
 endif
 perl_archlibexp		= @perl_archlibexp@
 perl_privlibexp		= @perl_privlibexp@
+perl_embed_ccflags	= @perl_embed_ccflags@
 perl_embed_ldflags	= @perl_embed_ldflags@
 
 # Miscellaneous
diff --git a/src/pl/plperl/GNUmakefile b/src/pl/plperl/GNUmakefile
@@ -12,7 +12,11 @@ override CPPFLAGS += -DPLPERL_HAVE_UID_GID
 override CPPFLAGS += -Wno-comment
 endif
 
-override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS) -I$(perl_archlibexp)/CORE
+# Note: we need to make sure that the CORE directory is included last,
+# probably because it sometimes contains some header files with names
+# that clash with some of ours, or with some that we include, notably on
+# Windows.
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS) $(perl_embed_ccflags) -I$(perl_archlibexp)/CORE
 
 rpathdir = $(perl_archlibexp)/CORE
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
@@ -517,7 +517,26 @@ sub mkvcbuild
 		my $plperl =
 		  $solution->AddProject('plperl', 'dll', 'PLs', 'src/pl/plperl');
 		$plperl->AddIncludeDir($solution->{options}->{perl} . '/lib/CORE');
-		$plperl->AddDefine('PLPERL_HAVE_UID_GID');
+
+		# Add defines from Perl's ccflags; see PGAC_CHECK_PERL_EMBED_CCFLAGS
+		my @perl_embed_ccflags;
+		foreach my $f (split(" ",$Config{ccflags}))
+		{
+			if ($f =~ /^-D[^_]/)
+			{
+				$f =~ s/\-D//;
+				push(@perl_embed_ccflags, $f);
+			}
+		}
+
+		# XXX this probably is redundant now?
+		push(@perl_embed_ccflags, 'PLPERL_HAVE_UID_GID');
+
+		foreach my $f (@perl_embed_ccflags)
+		{
+			$plperl->AddDefine($f);
+		}
+
 		foreach my $xs ('SPI.xs', 'Util.xs')
 		{
 			(my $xsc = $xs) =~ s/\.xs/.c/;
@@ -601,7 +620,11 @@ sub mkvcbuild
 			'hstore_plperl', 'contrib/hstore_plperl',
 			'plperl',        'src/pl/plperl',
 			'hstore',        'contrib/hstore');
-		$hstore_plperl->AddDefine('PLPERL_HAVE_UID_GID');
+
+		foreach my $f (@perl_embed_ccflags)
+		{
+			$hstore_plperl->AddDefine($f);
+		}
 	}
 
 	$mf =
