Prevent accidental linking of system-supplied copies of libpq.so etc.

Back-patch commit dddfc4cb, which broke LDFLAGS and related Makefile
variables into two parts, one for within-build-tree library references and
one for external libraries, to ensure that the order of -L flags has all
of the former before all of the latter.  This turns out to fix a problem
recently noted on buildfarm member peripatus, that we attempted to
incorporate code from libpgport.a into a shared library.  That will fail on
platforms that are sticky about putting non-PIC code into shared libraries.
(It's quite surprising we hadn't seen such failures before, since the code
in question has been like that for a long time.)

I think that peripatus' problem could have been fixed with just a subset
of this patch; but since the previous issue of accidentally linking to the
wrong copy of a Postgres shlib seems likely to bite people in the field,
let's just back-patch the whole change.  Now that commit dddfc4cb has
survived some beta testing, I'm less afraid to back-patch it than I was
at the time.

This also fixes undesired inclusion of "-DFRONTEND" in pg_config's CPPFLAGS
output (in 9.6 and up) and undesired inclusion of "-L../../src/common" in
its LDFLAGS output (in all supported branches).

Back-patch to v10 and older branches; this is already in v11.

Discussion: https://postgr.es/m/20180704234304.bq2dxispefl65odz@ler-imac.local

contrib/dblink/Makefile

@@ -3,7 +3,7 @@
 MODULE_big = dblink
 OBJS	= dblink.o $(WIN32RES)
 PG_CPPFLAGS = -I$(libpq_srcdir)
-SHLIB_LINK = $(libpq)
+SHLIB_LINK_INTERNAL = $(libpq)
 
 EXTENSION = dblink
 DATA = dblink--1.2.sql dblink--1.1--1.2.sql dblink--1.0--1.1.sql \

contrib/hstore_plperl/Makefile

@@ -27,16 +27,18 @@ endif
 # dependency.  This does preclude pgxs builds.
 ifeq ($(PORTNAME), aix)
 rpathdir = $(pkglibdir):$(perl_archlibexp)/CORE
-SHLIB_LINK += ../hstore/libhstore.exp $(perl_embed_ldflags)
+SHLIB_LINK_INTERNAL += ../hstore/libhstore.exp
+SHLIB_LINK += $(perl_embed_ldflags)
 endif
 ifeq ($(PORTNAME), win32)
 # these settings are the same as for plperl
 override CPPFLAGS += -DPLPERL_HAVE_UID_GID -Wno-comment
-SHLIB_LINK += ../hstore/libhstore.a $(sort $(wildcard ../../src/pl/plperl/libperl*.a))
+SHLIB_LINK_INTERNAL += ../hstore/libhstore.a $(sort $(wildcard ../../src/pl/plperl/libperl*.a))
 endif
 
 ifeq ($(PORTNAME), cygwin)
-SHLIB_LINK += -L../hstore -l hstore $(perl_embed_ldflags)
+SHLIB_LINK_INTERNAL += -L../hstore -l hstore
+SHLIB_LINK += $(perl_embed_ldflags)
 endif
 
 # As with plperl we need to make sure that the CORE directory is included

contrib/hstore_plpython/Makefile

@@ -27,15 +27,17 @@ endif
 # dependency.  This does preclude pgxs builds.
 ifeq ($(PORTNAME), aix)
 rpathdir = $(pkglibdir):$(python_libdir)
-SHLIB_LINK += ../hstore/libhstore.exp $(python_libspec) $(python_additional_libs) $(sort $(wildcard ../../src/pl/plpython/libplpython*.exp))
+SHLIB_LINK_INTERNAL += ../hstore/libhstore.exp $(sort $(wildcard ../../src/pl/plpython/libplpython*.exp))
+SHLIB_LINK += $(python_libspec) $(python_additional_libs)
 endif
 ifeq ($(PORTNAME), win32)
-SHLIB_LINK += ../hstore/libhstore.a $(sort $(wildcard ../../src/pl/plpython/libpython*.a)) $(sort $(wildcard ../../src/pl/plpython/libplpython*.a))
+SHLIB_LINK_INTERNAL += ../hstore/libhstore.a $(sort $(wildcard ../../src/pl/plpython/libplpython*.a)) $(sort $(wildcard ../../src/pl/plpython/libpython*.a))
 endif
 
 ifeq ($(PORTNAME), cygwin)
-SHLIB_LINK += -L../hstore -lhstore -L../../src/pl/plpython \
-	-lplpython$(python_majorversion) $(python_libspec)
+SHLIB_LINK_INTERNAL += -L../hstore -lhstore -L../../src/pl/plpython \
+	-lplpython$(python_majorversion)
+SHLIB_LINK += $(python_libspec)
 endif
 
 REGRESS_OPTS += --load-extension=hstore

contrib/ltree_plpython/Makefile

@@ -27,15 +27,17 @@ endif
 # dependency.  This does preclude pgxs builds.
 ifeq ($(PORTNAME), aix)
 rpathdir = $(pkglibdir):$(python_libdir)
-SHLIB_LINK += $(python_libspec) $(python_additional_libs) $(sort $(wildcard ../../src/pl/plpython/libplpython*.exp))
+SHLIB_LINK_INTERNAL += $(sort $(wildcard ../../src/pl/plpython/libplpython*.exp))
+SHLIB_LINK += $(python_libspec) $(python_additional_libs)
 endif
 ifeq ($(PORTNAME), win32)
-SHLIB_LINK += $(sort $(wildcard ../../src/pl/plpython/libpython*.a)) $(sort $(wildcard ../../src/pl/plpython/libplpython*.a))
+SHLIB_LINK_INTERNAL += $(sort $(wildcard ../../src/pl/plpython/libplpython*.a)) $(sort $(wildcard ../../src/pl/plpython/libpython*.a))
 endif
 
 ifeq ($(PORTNAME), cygwin)
-SHLIB_LINK += -L../ltree -lltree -L../../src/pl/plpython \
-	-lplpython$(python_majorversion) $(python_libspec)
+SHLIB_LINK_INTERNAL += -L../ltree -lltree -L../../src/pl/plpython \
+	-lplpython$(python_majorversion)
+SHLIB_LINK += $(python_libspec)
 endif
 
 REGRESS_OPTS += --load-extension=ltree

contrib/oid2name/Makefile

@@ -7,7 +7,7 @@ PROGRAM = oid2name
 OBJS	= oid2name.o $(WIN32RES)
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-PG_LIBS = $(libpq_pgport)
+PG_LIBS_INTERNAL = $(libpq_pgport)
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config

contrib/postgres_fdw/Makefile

@@ -5,7 +5,7 @@ OBJS = postgres_fdw.o option.o deparse.o connection.o shippable.o $(WIN32RES)
 PGFILEDESC = "postgres_fdw - foreign data wrapper for PostgreSQL"
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-SHLIB_LINK = $(libpq)
+SHLIB_LINK_INTERNAL = $(libpq)
 
 EXTENSION = postgres_fdw
 DATA = postgres_fdw--1.0.sql

contrib/spi/Makefile

@@ -17,8 +17,6 @@ DOCS = $(addsuffix .example, $(MODULES))
 # comment out if you want a quieter refint package for other uses
 PG_CPPFLAGS = -DREFINT_VERBOSE
 
-LDFLAGS_SL += -L$(top_builddir)/src/port -lpgport
-
 ifdef USE_PGXS
 PG_CONFIG = pg_config
 PGXS := $(shell $(PG_CONFIG) --pgxs)

contrib/vacuumlo/Makefile

@@ -7,7 +7,7 @@ PROGRAM = vacuumlo
 OBJS	= vacuumlo.o $(WIN32RES)
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-PG_LIBS = $(libpq_pgport)
+PG_LIBS_INTERNAL = $(libpq_pgport)
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config

src/Makefile.global.in

@@ -267,17 +267,26 @@ LD = @LD@
 with_gnu_ld = @with_gnu_ld@
 ld_R_works = @ld_R_works@
 
-# We want -L for libpgport.a and libpgcommon.a to be first in LDFLAGS.  We
-# also need LDFLAGS to be a "recursively expanded" variable, else adjustments
-# to rpathdir don't work right.  So we must NOT do LDFLAGS := something,
-# meaning this has to be done first and elsewhere we must only do LDFLAGS +=
-# something.
+# It's critical that within LDFLAGS, all -L switches pointing to build-tree
+# directories come before any -L switches pointing to external directories.
+# Otherwise it's possible for, e.g., a platform-provided copy of libpq.so
+# to get linked in place of the one we've built.  Therefore we adopt the
+# convention that the first component of LDFLAGS is an extra variable
+# LDFLAGS_INTERNAL, and -L and -l switches for PG's own libraries must be
+# put into LDFLAGS_INTERNAL, so they will appear ahead of those for external
+# libraries.
+#
+# We need LDFLAGS and LDFLAGS_INTERNAL to be "recursively expanded" variables,
+# else adjustments to, e.g., rpathdir don't work right.  So we must NOT do
+# "LDFLAGS := something" anywhere, ditto for LDFLAGS_INTERNAL.
+# These initial assignments must be "=" type, and elsewhere we must only do
+# "LDFLAGS += something" or "LDFLAGS_INTERNAL += something".
 ifdef PGXS
-  LDFLAGS = -L$(libdir)
+  LDFLAGS_INTERNAL = -L$(libdir)
 else
-  LDFLAGS = -L$(top_builddir)/src/port -L$(top_builddir)/src/common
+  LDFLAGS_INTERNAL = -L$(top_builddir)/src/port -L$(top_builddir)/src/common
 endif
-LDFLAGS += @LDFLAGS@
+LDFLAGS = $(LDFLAGS_INTERNAL) @LDFLAGS@
 
 LDFLAGS_EX = @LDFLAGS_EX@
 # LDFLAGS_SL might have already been assigned by calling makefile

src/Makefile.shlib

@@ -20,12 +20,16 @@
 #
 # NAME                  Name of library to build (no suffix nor "lib" prefix)
 # OBJS                  List of object files to include in library
-# SHLIB_LINK            If shared library relies on other libraries,
-#                       additional stuff to put in its link command
+# SHLIB_LINK            Stuff to append to library's link command
+#                       (typically, -L and -l switches for external libraries)
+# SHLIB_LINK_INTERNAL   -L and -l switches for Postgres-supplied libraries
 # SHLIB_PREREQS         Order-only prerequisites for library build target
 # SHLIB_EXPORTS         (optional) Name of file containing list of symbols to
 #                       export, in the format "function_name  number"
 #
+# Don't use SHLIB_LINK for references to files in the build tree, or the
+# wrong things will happen --- use SHLIB_LINK_INTERNAL for those!
+#
 # When building a shared library, the following version information
 # must also be set.  It should be omitted when building a dynamically
 # loadable module.
@@ -70,6 +74,8 @@
 COMPILER = $(CC) $(CFLAGS)
 LINK.static = $(AR) $(AROPT)
 
+LDFLAGS_INTERNAL += $(SHLIB_LINK_INTERNAL)
+
 
 
 ifdef SO_MAJOR_VERSION

src/backend/replication/libpqwalreceiver/Makefile

@@ -15,7 +15,8 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
 
 OBJS = libpqwalreceiver.o $(WIN32RES)
-SHLIB_LINK = $(libpq) $(filter -lintl, $(LIBS))
+SHLIB_LINK_INTERNAL = $(libpq)
+SHLIB_LINK = $(filter -lintl, $(LIBS))
 SHLIB_PREREQS = submake-libpq
 PGFILEDESC = "libpqwalreceiver - receive WAL during streaming replication"
 NAME = libpqwalreceiver

src/bin/pg_basebackup/Makefile

@@ -17,19 +17,20 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) $(CPPFLAGS)
+LDFLAGS_INTERNAL += $(libpq_pgport)
 
 OBJS=receivelog.o streamutil.o $(WIN32RES)
 
 all: pg_basebackup pg_receivexlog pg_recvlogical
 
 pg_basebackup: pg_basebackup.o $(OBJS) | submake-libpq submake-libpgport
-	$(CC) $(CFLAGS) pg_basebackup.o $(OBJS) $(libpq_pgport) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
+	$(CC) $(CFLAGS) pg_basebackup.o $(OBJS) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
 pg_receivexlog: pg_receivexlog.o $(OBJS) | submake-libpq submake-libpgport
-	$(CC) $(CFLAGS) pg_receivexlog.o $(OBJS) $(libpq_pgport) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
+	$(CC) $(CFLAGS) pg_receivexlog.o $(OBJS) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
 pg_recvlogical: pg_recvlogical.o $(OBJS) | submake-libpq submake-libpgport
-	$(CC) $(CFLAGS) pg_recvlogical.o $(OBJS) $(libpq_pgport) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
+	$(CC) $(CFLAGS) pg_recvlogical.o $(OBJS) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
 install: all installdirs
 	$(INSTALL_PROGRAM) pg_basebackup$(X) '$(DESTDIR)$(bindir)/pg_basebackup$(X)'

src/bin/pg_ctl/Makefile

@@ -17,13 +17,14 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) $(CPPFLAGS)
+LDFLAGS_INTERNAL += $(libpq_pgport)
 
 OBJS=	pg_ctl.o $(WIN32RES)
 
 all: pg_ctl
 
 pg_ctl: $(OBJS) | submake-libpq submake-libpgport
-	$(CC) $(CFLAGS) $(OBJS) $(libpq_pgport) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
+	$(CC) $(CFLAGS) $(OBJS) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)
 
 install: all installdirs
 	$(INSTALL_PROGRAM) pg_ctl$(X) '$(DESTDIR)$(bindir)/pg_ctl$(X)'

src/bin/pg_dump/Makefile

@@ -17,7 +17,7 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) $(CPPFLAGS)
-override LDFLAGS := -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 OBJS=	pg_backup_archiver.o pg_backup_db.o pg_backup_custom.o \
 	pg_backup_null.o pg_backup_tar.o pg_backup_directory.o \

src/bin/pg_rewind/Makefile

@@ -16,7 +16,7 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) -DFRONTEND $(CPPFLAGS)
-override LDFLAGS := $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += $(libpq_pgport)
 
 OBJS	= pg_rewind.o parsexlog.o xlogreader.o datapagemap.o timeline.o \
 	fetch.o file_ops.o copy_fetch.o libpq_fetch.o filemap.o logging.o \

src/bin/pg_upgrade/Makefile

@@ -12,7 +12,7 @@ OBJS = check.o controldata.o dump.o exec.o file.o function.o info.o \
        tablespace.o util.o version.o $(WIN32RES)
 
 override CPPFLAGS := -DDLSUFFIX=\"$(DLSUFFIX)\" -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
-override LDFLAGS := -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 
 all: pg_upgrade

src/bin/pgbench/Makefile

@@ -10,7 +10,7 @@ include $(top_builddir)/src/Makefile.global
 OBJS = pgbench.o exprparse.o $(WIN32RES)
 
 override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
-override LDFLAGS := -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 ifneq ($(PORTNAME), win32)
 override CFLAGS += $(PTHREAD_CFLAGS)

src/bin/psql/Makefile

@@ -19,7 +19,7 @@ include $(top_builddir)/src/Makefile.global
 REFDOCDIR= $(top_srcdir)/doc/src/sgml/ref
 
 override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
-override LDFLAGS := -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 OBJS=	command.o common.o help.o input.o stringutils.o mainloop.o copy.o \
 	startup.o prompt.o variables.o large_obj.o describe.o \

src/bin/scripts/Makefile

@@ -19,7 +19,7 @@ include $(top_builddir)/src/Makefile.global
 PROGRAMS = createdb createlang createuser dropdb droplang dropuser clusterdb vacuumdb reindexdb pg_isready
 
 override CPPFLAGS := -I$(libpq_srcdir) $(CPPFLAGS)
-override LDFLAGS := -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(LDFLAGS)
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 all: $(PROGRAMS)
 

src/common/Makefile

@@ -20,12 +20,9 @@ subdir = src/common
 top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 
-override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
-LIBS += $(PTHREAD_LIBS)
-
 # don't include subdirectory-path-dependent -I and -L switches
 STD_CPPFLAGS := $(filter-out -I$(top_srcdir)/src/include -I$(top_builddir)/src/include,$(CPPFLAGS))
-STD_LDFLAGS := $(filter-out -L$(top_builddir)/src/port,$(LDFLAGS))
+STD_LDFLAGS := $(filter-out -L$(top_builddir)/src/common -L$(top_builddir)/src/port,$(LDFLAGS))
 override CPPFLAGS += -DVAL_CONFIGURE="\"$(configure_args)\""
 override CPPFLAGS += -DVAL_CC="\"$(CC)\""
 override CPPFLAGS += -DVAL_CPPFLAGS="\"$(STD_CPPFLAGS)\""
@@ -36,6 +33,9 @@ override CPPFLAGS += -DVAL_LDFLAGS_EX="\"$(LDFLAGS_EX)\""
 override CPPFLAGS += -DVAL_LDFLAGS_SL="\"$(LDFLAGS_SL)\""
 override CPPFLAGS += -DVAL_LIBS="\"$(LIBS)\""
 
+override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
+LIBS += $(PTHREAD_LIBS)
+
 OBJS_COMMON = config_info.o controldata_utils.o exec.o keywords.o \
 	pg_lzcompress.o pgfnames.o psprintf.o relpath.o rmtree.o \
 	string.o username.o wait_error.o