Build src/port files as a library with -fPIC, and use that in libpq.

libpq and ecpg need shared-library-friendly versions of assorted src/port/
and src/common/ modules.  Up to now, they got those by symlinking the
individual source files and compiling them locally.  That's baroque, and a
pain to maintain, and it results in some amount of duplicated compile work.
It might've made sense when only a couple of files were needed, but the
list has grown and grown and grown :-(

It makes more sense to have the originating directory build a third variant
of libpgport.a/libpgcommon.a containing modules built with $(CFLAGS_SL),
and just link that into the shared library.  Unused files won't get linked,
so the end result should be the same.

This patch makes a down payment on that idea by having src/port/ build
such a library and making libpq use it.  If the buildfarm doesn't expose
fatal problems with the approach, I'll extend it to the other cases.

Discussion: https://postgr.es/m/[email protected]

1 files changed, 43 insertions, 12 deletions

diff --git a/src/port/Makefile b/src/port/Makefile
index a2ee8e2d6d0..ec62a31d29f 100644
--- a/src/port/Makefile
+++ b/src/port/Makefile
@@ -1,18 +1,23 @@
 #-------------------------------------------------------------------------
 #
 # Makefile
-#    Makefile for the port-specific subsystem of the backend
+#    Makefile for src/port
 #
-# These files are used in other directories for portability on systems
-# with broken/missing library files, and for common code sharing.
+# These files are used by the Postgres backend, and also by frontend
+# programs.  Primarily, they are meant to provide portability on systems
+# with broken/missing library files.
 #
-# This makefile generates two outputs:
+# This makefile generates three outputs:
 #
 #	libpgport.a - contains object files with FRONTEND defined,
-#		for use by client application and libraries
+#		for use by client applications
+#
+#	libpgport_shlib.a - contains object files with FRONTEND defined,
+#		built suitably for use in shared libraries; for use
+#		by libpq and other frontend libraries
 #
 #	libpgport_srv.a - contains object files without FRONTEND defined,
-#		for use only by the backend binaries
+#		for use only by the backend
 #
 # LIBOBJS is set by configure (via Makefile.global) to be the list of object
 # files that are conditionally needed as determined by configure's probing.
@@ -40,12 +45,15 @@ ifeq ($(enable_strong_random), yes)
 OBJS += pg_strong_random.o
 endif
 
-# foo_srv.o and foo.o are both built from foo.c, but only foo.o has -DFRONTEND
+# libpgport.a, libpgport_shlib.a, and libpgport_srv.a contain the same files
+# foo.o, foo_shlib.o, and foo_srv.o are all built from foo.c
+OBJS_SHLIB = $(OBJS:%.o=%_shlib.o)
 OBJS_SRV = $(OBJS:%.o=%_srv.o)
 
-all: libpgport.a libpgport_srv.a
+all: libpgport.a libpgport_shlib.a libpgport_srv.a
 
 # libpgport is needed by some contrib
+# currently we don't install libpgport_shlib.a, maybe we should?
 install: all installdirs
 	$(INSTALL_STLIB) libpgport.a '$(DESTDIR)$(libdir)/libpgport.a'
 
@@ -59,18 +67,38 @@ libpgport.a: $(OBJS)
 	rm -f $@
 	$(AR) $(AROPT) $@ $^
 
-# thread.o needs PTHREAD_CFLAGS (but thread_srv.o does not)
+# thread.o and thread_shlib.o need PTHREAD_CFLAGS (but thread_srv.o does not)
 thread.o: CFLAGS+=$(PTHREAD_CFLAGS)
+thread_shlib.o: CFLAGS+=$(PTHREAD_CFLAGS)
 
-# pg_crc32c_sse42.o and its _srv.o version need CFLAGS_SSE42
+# all versions of pg_crc32c_sse42.o need CFLAGS_SSE42
 pg_crc32c_sse42.o: CFLAGS+=$(CFLAGS_SSE42)
+pg_crc32c_sse42_shlib.o: CFLAGS+=$(CFLAGS_SSE42)
 pg_crc32c_sse42_srv.o: CFLAGS+=$(CFLAGS_SSE42)
 
-# pg_crc32c_armv8.o and its _srv.o version need CFLAGS_ARMV8_CRC32C
+# all versions of pg_crc32c_armv8.o need CFLAGS_ARMV8_CRC32C
 pg_crc32c_armv8.o: CFLAGS+=$(CFLAGS_ARMV8_CRC32C)
+pg_crc32c_armv8_shlib.o: CFLAGS+=$(CFLAGS_ARMV8_CRC32C)
 pg_crc32c_armv8_srv.o: CFLAGS+=$(CFLAGS_ARMV8_CRC32C)
 
 #
+# Shared library versions of object files
+#
+
+libpgport_shlib.a: $(OBJS_SHLIB)
+	rm -f $@
+	$(AR) $(AROPT) $@ $^
+
+# Because this uses its own compilation rule, it doesn't use the
+# dependency tracking logic from Makefile.global.  To make sure that
+# dependency tracking works anyway for the *_shlib.o files, depend on
+# their *.o siblings as well, which do have proper dependencies.  It's
+# a hack that might fail someday if there is a *_shlib.o without a
+# corresponding *.o, but there seems little reason for that.
+%_shlib.o: %.c %.o
+	$(CC) $(CFLAGS) $(CFLAGS_SL) $(CPPFLAGS) -c $< -o $@
+
+#
 # Server versions of object files
 #
 
@@ -92,6 +120,8 @@ libpgport_srv.a: $(OBJS_SRV)
 
 path.o: path.c pg_config_paths.h
 
+path_shlib.o: path.c pg_config_paths.h
+
 path_srv.o: path.c pg_config_paths.h
 
 # We create a separate file rather than put these in pg_config.h
@@ -112,4 +142,5 @@ pg_config_paths.h: $(top_builddir)/src/Makefile.global
 	echo "#define MANDIR \"$(mandir)\"" >>$@
 
 clean distclean maintainer-clean:
-	rm -f libpgport.a libpgport_srv.a $(OBJS) $(OBJS_SRV) pg_config_paths.h
+	rm -f libpgport.a libpgport_shlib.a libpgport_srv.a
+	rm -f $(OBJS) $(OBJS_SHLIB) $(OBJS_SRV) pg_config_paths.h