Thread: Dynamic linking on AIX
This patch fixes linking on AIX. Relevant threads on psql-hackers: http://archives.postgresql.org/pgsql-hackers/2006-09/msg01020.php http://archives.postgresql.org/pgsql-hackers/2006-09/msg01084.php http://archives.postgresql.org/pgsql-hackers/2006-09/msg01109.php Up to now, the default on AIX was to link statically. This was not intended; it's just that AIX has different ideas about shared libraries than Linux and nobody cared. --enable-rpath was matched to the AIX equivalent. I tested the patch on AIX 5.3 with gcc; it should also work with IBM's cc. The patch is backward compatible until AIX 4.3 at least, and I added a kludge to Makefile.shlib so that it should also build something operational on AIX 3.2.5. The change to src/interfaces/ecpg/test/Makefile.regress is not actually part of the patch, but without it building fails if you configure --with-ldap --disable-shared I tested building with --disable-shared and --enable-shared (with --enable-rpath and --disable-rpath). Yours, Laurenz Albe
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This is a second try; this patch replaces http://archives.postgresql.org/pgsql-patches/2006-09/msg00185.php Incorporated are - Tom Lane's suggestions for a more sane approach at fixing Makefile.shlib - Rocco Altier's additions to make the regression test run by setting LIBPATH appropriately. - Two changes in /src/interfaces/ecpg/test/Makefile.regress and src/interfaces/ecpg/test/compat_informix/Makefile without which 'make' fails if configure was called with --disable-shared (this is not AIX-specific). The line in src/makefiles/Makefile.aix where I set 'libpath' also seems pretty ugly to me. Do you have a better idea? Basically I need to convert LDFLAGS like: -L../../dir -L /extra/lib -lalib -Wl,yxz -L/more/libs to :/extra/lib:/more/libs and couldn't think of a better way to do it. It will fail if there is a -L path that contains a blank :^( Yours, Laurenz Albe
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I still would like to see a paragraph describing how AIX is different from other platforms and what we are doing here. --------------------------------------------------------------------------- Albe Laurenz wrote: > This is a second try; this patch replaces > http://archives.postgresql.org/pgsql-patches/2006-09/msg00185.php > > Incorporated are > - Tom Lane's suggestions for a more sane approach at > fixing Makefile.shlib > - Rocco Altier's additions to make the regression test run > by setting LIBPATH appropriately. > - Two changes in /src/interfaces/ecpg/test/Makefile.regress > and src/interfaces/ecpg/test/compat_informix/Makefile > without which 'make' fails if configure was called > with --disable-shared (this is not AIX-specific). > > The line in src/makefiles/Makefile.aix > where I set 'libpath' also seems pretty ugly to me. > Do you have a better idea? > > Basically I need to convert LDFLAGS like: > -L../../dir -L /extra/lib -lalib -Wl,yxz -L/more/libs > to > :/extra/lib:/more/libs > and couldn't think of a better way to do it. > > It will fail if there is a -L path that contains > a blank :^( > > Yours, > Laurenz Albe Content-Description: aixlink2.patch [ Attachment, skipping... ] > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
> I still would like to see a paragraph describing how AIX is different > from other platforms and what we are doing here. Ok, I'll try to sum it up: Shared libraries in AIX are different from shared libraries in Linux. A shared library on AIX is an 'ar' archive containing shared objects. A shared object is produced by the linker when invoked appropriately (e.g. with -G), it is what we call a shared library on Linux. -> On AIX, you can do a static as well as a dynamic -> link against a shared library, it depends on how you -> invoke the linker. When you link statically, the shared objects from the library are added to your executable as required; when you link dynamically, only references to the shared objects are included in the executable. Consequently you do not need a separate static library on AIX if you have a dynamic library. However, you CAN have static libraries (ar archives containing *.o files), and the linker will link against them. This will of course always be a static link. When the AIX linker searches for libraries to link, it will look for a library libxy.a as well as for a single shared object libxy.so when you tell it to -lyx. When it finds both in the same directory, it will prefer libpq.a unless invoked with -brtl. This is where the problem occurs: By default, PostgreSQL will (in the Linux way) create a shared object libpq.so and a static library libpq.a in the same directory. Up to now, since the linker was invoked without the -brtl flag, linking on AIX was always static, as the linker preferred libpq.a over libpq.so. We could have solved the problem by linking with -brtl on AIX, but we chose to go a more AIX-conforming way so that third party programs linking against PostgreSQL libraries will not be fooled into linking statically by default. The 'new way' on AIX is: - Create libxy.so.n as before from the static library libxy.a with the linker. - Remove libxy.a - Recreate libxy.a as a dynamic library with ar -cr libxy.a libxy.so.n - Only install libxy.a, do not install libxy.so Since linking is dynamic on AIX now, we have a new problem: We must make sure that the executable finds its library even if the library is not installed in one of the standard library paths (/usr/lib or /lib). On Linux this is done with an RPATH, on AIX the equivalent is LIBPATH that can be specified at link time with -blibpath:<colon separated path> . If you do not specify the LIBPATH, it is automatically computed from the -L arguments given to the linker. The LIBPATH, when set, must contain ALL directories where shared libraries should be searched, including the standard library directories. Makefile.aix has been changed to link executables with a LIBPATH that contains --libdir when PostgreSQL is configured with --enable-rpath (the default). The AIX equivalent for the Linux environment variable LD_LIBRARY_PATH is LIBPATH. The regression tests rely on LD_LIBRARY_PATH and have to be changed to set LIBPATH as well. I hope that's good enough, Laurenz Albe
"Albe Laurenz" <all@adv.magwien.gv.at> writes: > This is a second try; this patch replaces > http://archives.postgresql.org/pgsql-patches/2006-09/msg00185.php Looks good, applied. > The line in src/makefiles/Makefile.aix > where I set 'libpath' also seems pretty ugly to me. > It will fail if there is a -L path that contains > a blank :^( We were already assuming no spaces in -L switches, see the $filter manipulations in Makefile.shlib. So I simplified it to libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib It's annoying to have to shell out to sed to get rid of the spaces, but this is gmake's fault for having such a brain-dead function call syntax. After looking at the gmake manual, it is possible to use $subst to get rid of spaces, but it's even uglier (and much harder to follow) than the above ... regards, tom lane
Great, I have added this to the bottom of the AIX FAQ. Thanks. --------------------------------------------------------------------------- Albe Laurenz wrote: > > I still would like to see a paragraph describing how AIX is different > > from other platforms and what we are doing here. > > Ok, I'll try to sum it up: > > Shared libraries in AIX are different from shared libraries > in Linux. > > A shared library on AIX is an 'ar' archive containing > shared objects. > A shared object is produced by the linker when invoked > appropriately (e.g. with -G), it is what we call a > shared library on Linux. > > -> On AIX, you can do a static as well as a dynamic > -> link against a shared library, it depends on how you > -> invoke the linker. > > When you link statically, the shared objects from > the library are added to your executable as required; > when you link dynamically, only references > to the shared objects are included in the executable. > > Consequently you do not need a separate static library > on AIX if you have a dynamic library. > > However, you CAN have static libraries (ar archives > containing *.o files), and the linker will link > against them. This will of course always be a > static link. > > When the AIX linker searches for libraries to link, > it will look for a library libxy.a as well as for a > single shared object libxy.so when you tell it > to -lyx. When it finds both in the same directory, > it will prefer libpq.a unless invoked with -brtl. > > This is where the problem occurs: > > By default, PostgreSQL will (in the Linux way) create > a shared object libpq.so and a static library libpq.a > in the same directory. > > Up to now, since the linker was invoked without the > -brtl flag, linking on AIX was always static, as the > linker preferred libpq.a over libpq.so. > > We could have solved the problem by linking with > -brtl on AIX, but we chose to go a more AIX-conforming > way so that third party programs linking against > PostgreSQL libraries will not be fooled into > linking statically by default. > > The 'new way' on AIX is: > - Create libxy.so.n as before from the static library > libxy.a with the linker. > - Remove libxy.a > - Recreate libxy.a as a dynamic library with > ar -cr libxy.a libxy.so.n > - Only install libxy.a, do not install libxy.so > > Since linking is dynamic on AIX now, we have a new > problem: > > We must make sure that the executable finds > its library even if the library is not installed in > one of the standard library paths (/usr/lib or /lib). > > On Linux this is done with an RPATH, on AIX the > equivalent is LIBPATH that can be specified at link > time with -blibpath:<colon separated path> . > If you do not specify the LIBPATH, it is automatically > computed from the -L arguments given to the linker. > The LIBPATH, when set, must contain ALL directories where > shared libraries should be searched, including > the standard library directories. > > Makefile.aix has been changed to link executables > with a LIBPATH that contains --libdir when PostgreSQL > is configured with --enable-rpath (the default). > > The AIX equivalent for the Linux environment variable > LD_LIBRARY_PATH is LIBPATH. > > The regression tests rely on LD_LIBRARY_PATH and have > to be changed to set LIBPATH as well. > > > I hope that's good enough, > Laurenz Albe > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
bruce@momjian.us (Bruce Momjian) writes: > Great, I have added this to the bottom of the AIX FAQ. Thanks. It seems to me that this also warrants an entry in the release notes. I'd think that an entry in the Source Code Changes section, immediately after the "Reduce libraries linked into the backend needlessly" might read: * Add shared library support for AIX -- let name="cbbrowne" and tld="linuxdatabases.info" in String.concat "@" [name;tld];; http://linuxdatabases.info/info/wp.html "I'd crawl over an acre of 'Visual This++' and 'Integrated Development That' to get to gcc, Emacs, and gdb. Thank you." -- Vance Petree, Virginia Power
Chris Browne wrote: > bruce@momjian.us (Bruce Momjian) writes: > > Great, I have added this to the bottom of the AIX FAQ. Thanks. > > It seems to me that this also warrants an entry in the release notes. > > I'd think that an entry in the Source Code Changes section, > immediately after the "Reduce libraries linked into the backend > needlessly" might read: > > * Add shared library support for AIX Done. -- Bruce Momjian bruce@momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +