Re: [PATCHES] [HACKERS] Should libedit be preferred to libreadline?
Bruce Momjian wrote: > Why don't we have a libedit configure flag? Well, I can code up a configure flag, but that doesn't mean that the thing will compile at the end. :) -- Peter Eisentraut http://developer.postgresql.org/~petere/ ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [HACKERS] Should libedit be preferred to libreadline?
Jim C. Nasby wrote: > On Mon, Nov 21, 2005 at 07:50:48PM -0500, Andrew Dunstan wrote: > > > > Nice analysis, but we can't hack configure like that. It has to be able > > to be fully generated from its sources. I think the other source file > > you would need to look at is config/programs.m4. (Not sure about quoting > > $ac_popdir - why only that one?) > > > > Also, I suspect we'd want to enable the libedit preference with a switch > > rather than just force it, if we want to go this way. > > BTW, we've run into issues with readline from a licensing standpoint. It > would be really nice if libedit was supported where practical (I suspect > most mainstream OSes support libedit) since it's BSD licensed. Why don't we have a libedit configure flag? -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] Should libedit be preferred to libreadline?
Martijn van Oosterhout wrote: -- Start of PGP signed section. > On Tue, Nov 22, 2005 at 10:07:15AM +0100, Zeugswetter Andreas DCP SD wrote: > > PS: I'd prefer if readline was only linked where it is needed, namely in > > psql. > > The problem as stated is that people don't want to maintain lists of > libraries as needed by each program, so we link all of them. > > Since it seems to always be the same few libraries that cause us > problems, maybe a simpler approach would be to, in the Makefile, use > filter-out to exclude libraries you *know* aren't needed. Like in the > Makefile we put: > > postgres: $(OBJS) > $(CC) $(CFLAGS) $(LDFLAGS) $(export_dynamic) $^ $(filter-out > -lreadline -ledit, $(LIBS)) -o $@ Agreed. I have no idea why this has not been done already. -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: [HACKERS] Should libedit be preferred to libreadline?
On Mon, Nov 21, 2005 at 07:50:48PM -0500, Andrew Dunstan wrote: > > Nice analysis, but we can't hack configure like that. It has to be able > to be fully generated from its sources. I think the other source file > you would need to look at is config/programs.m4. (Not sure about quoting > $ac_popdir - why only that one?) > > Also, I suspect we'd want to enable the libedit preference with a switch > rather than just force it, if we want to go this way. BTW, we've run into issues with readline from a licensing standpoint. It would be really nice if libedit was supported where practical (I suspect most mainstream OSes support libedit) since it's BSD licensed. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.comwork: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] Should libedit be preferred to libreadline?
On Tue, Nov 22, 2005 at 10:07:15AM +0100, Zeugswetter Andreas DCP SD wrote: > PS: I'd prefer if readline was only linked where it is needed, namely in > psql. The problem as stated is that people don't want to maintain lists of libraries as needed by each program, so we link all of them. Since it seems to always be the same few libraries that cause us problems, maybe a simpler approach would be to, in the Makefile, use filter-out to exclude libraries you *know* aren't needed. Like in the Makefile we put: postgres: $(OBJS) $(CC) $(CFLAGS) $(LDFLAGS) $(export_dynamic) $^ $(filter-out -lreadline -ledit, $(LIBS)) -o $@ So instead of maintaining lists of what each binary needs, we can maintain a few lists of what certain binaries *don't* need. Actually, I think the backend is the only thing important enough to worry about this, although if readline is exporting memcpy that it's quite possible other binaries might be affected. Maybe create a BACKEND_LIBS which contains a shorter list. Even the GCC --as-needed flag can't save you from libs exporting functions they shouldn't... Have a nice day, -- Martijn van Oosterhout http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them. pgp8Pn6BoBdmd.pgp Description: PGP signature
Re: [HACKERS] Should libedit be preferred to libreadline?
> With AIX 5, the easiest way to get a shared object is to pass "-bexpall" > to the linker. This results in all symbols being exported. Yes, that is another reason not to use this broken switch. And last time I checked (AIX 4.3.3), -bexpall did not export all needed symbols (e.g. globals) from the backend eighter. And the counterpart -bimpall did also not work. Dynamic loading did not work without the .imp and .exp files :-( Andreas PS: I'd prefer if readline was only linked where it is needed, namely in psql. ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] Should libedit be preferred to libreadline?
Andrew Dunstan <[EMAIL PROTECTED]> writes: > Also, I suspect we'd want to enable the libedit preference with a switch > rather than just force it, if we want to go this way. Quite. My recollection is that there are other platforms on which readline works and libedit is broken. (Readline used to work just fine even on AIX ;-)) regards, tom lane ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [HACKERS] Should libedit be preferred to libreadline?
Nice analysis, but we can't hack configure like that. It has to be able to be fully generated from its sources. I think the other source file you would need to look at is config/programs.m4. (Not sure about quoting $ac_popdir - why only that one?) Also, I suspect we'd want to enable the libedit preference with a switch rather than just force it, if we want to go this way. cheers andrew Seneca Cunningham wrote: It would certainly seem so on AIX. In tracking down why postgres 8.x would segfault on AIX 5.3, it became apparent to me that libreadline.a is a problematic library to link against and that libedit.a is preferable (and for reasons other than that readline is GPL while postgres is BSD-licensed). With AIX 5, the easiest way to get a shared object is to pass "-bexpall" to the linker. This results in all symbols being exported. The problem with this is that the linker will export all of libreadline's and libhistory's symbols. In the case of libreadline.so.4 (and .5) on AIX 5 this includes symbols like strncpy and memmove, but on .4, not memcpy. This is likely because libc.a does not export them. What results from this is that when postgres is linked against readline on AIX, it gets these memory functions through readline instead of its own code. When readline 4.3 is used (what IBM provides in their "AIX Toolbox for Linux"), postgres is known to crash. These segfaults (if postgres was compiled with gcc) have occurred on AIX 5.3ML3, AIX 5.3ML1, and AIX 5.2ML7. With readline 5.0, postgres merely gets these functions through the shared library memory segments instead of the user memory segments[6]. While it is possible to build libreadline in a manner that doesn't export strncpy, neither of the prebuilt readlines for AIX 5 that I checked were both shared and did not export strncpy. IBM's readline[5] exports strncpy, UCLA's readline[4] is static. Building a shared readline that doesn't export strncpy requires creating export files for libreadline and libhistory that only list the symbols that they are supposed to export and editing the shared library Makefile to add the exports flags to the appropriate linker calls. Whatever strategy we might take, using readline on AIX requires considerable trickery and hacking around with the build environments. Simply put, it's ghastly. On the other hand, the port of NetBSD's editline that I tried[1] works without build-hackery to the library and has reasonable exports. The only changes to postgres that I needed to make were confined to telling the configure script to check for libedit before libreadline and adding a test for histedit.h. The attached patch contains my modifications. It is also possible to use a wrapper like rlwrap[2] instead of linking postgres against libreadline or libedit. [1] port of NetBSD's editline http://www.thrysoee.dk/editline/ [2] rlwrap http://utopia.knoware.nl/~hlub/uck/software/ [3] IBM Redbook "AIX 5L Porting Guide", section 9.2 http://www.redbooks.ibm.com/abstracts/sg246034.html?Open http://www.redbooks.ibm.com/redbooks/pdfs/sg246034.pdf [4] UCLA's readline package http://aixpdslib.seas.ucla.edu/packages/readline.html [5] IBM's readline package http://www-03.ibm.com/servers/aix/products/aixos/linux/download.html [6] IBM Redbook "Developing and Porting C and C++ Applications on AIX", page 110 http://www.redbooks.ibm.com/abstracts/sg245674.html?Open http://www.redbooks.ibm.com/redbooks/pdfs/sg245674.pdf [patch snipped] ---(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
[HACKERS] Should libedit be preferred to libreadline?
It would certainly seem so on AIX.
In tracking down why postgres 8.x would segfault on AIX 5.3, it became
apparent to me that libreadline.a is a problematic library to link
against and that libedit.a is preferable (and for reasons other than
that readline is GPL while postgres is BSD-licensed).
With AIX 5, the easiest way to get a shared object is to pass "-bexpall"
to the linker. This results in all symbols being exported. The problem
with this is that the linker will export all of libreadline's and
libhistory's symbols. In the case of libreadline.so.4 (and .5) on AIX 5
this includes symbols like strncpy and memmove, but on .4, not memcpy.
This is likely because libc.a does not export them.
What results from this is that when postgres is linked against readline
on AIX, it gets these memory functions through readline instead of its
own code. When readline 4.3 is used (what IBM provides in their "AIX
Toolbox for Linux"), postgres is known to crash. These segfaults (if
postgres was compiled with gcc) have occurred on AIX 5.3ML3, AIX 5.3ML1,
and AIX 5.2ML7. With readline 5.0, postgres merely gets these functions
through the shared library memory segments instead of the user memory
segments[6].
While it is possible to build libreadline in a manner that doesn't
export strncpy, neither of the prebuilt readlines for AIX 5 that I
checked were both shared and did not export strncpy. IBM's readline[5]
exports strncpy, UCLA's readline[4] is static. Building a shared
readline that doesn't export strncpy requires creating export files for
libreadline and libhistory that only list the symbols that they are
supposed to export and editing the shared library Makefile to add the
exports flags to the appropriate linker calls.
Whatever strategy we might take, using readline on AIX requires
considerable trickery and hacking around with the build environments.
Simply put, it's ghastly.
On the other hand, the port of NetBSD's editline that I tried[1] works
without build-hackery to the library and has reasonable exports. The
only changes to postgres that I needed to make were confined to telling
the configure script to check for libedit before libreadline and adding
a test for histedit.h. The attached patch contains my modifications.
It is also possible to use a wrapper like rlwrap[2] instead of linking
postgres against libreadline or libedit.
[1] port of NetBSD's editline
http://www.thrysoee.dk/editline/
[2] rlwrap
http://utopia.knoware.nl/~hlub/uck/software/
[3] IBM Redbook "AIX 5L Porting Guide", section 9.2
http://www.redbooks.ibm.com/abstracts/sg246034.html?Open
http://www.redbooks.ibm.com/redbooks/pdfs/sg246034.pdf
[4] UCLA's readline package
http://aixpdslib.seas.ucla.edu/packages/readline.html
[5] IBM's readline package
http://www-03.ibm.com/servers/aix/products/aixos/linux/download.html
[6] IBM Redbook "Developing and Porting C and C++ Applications on AIX",
page 110
http://www.redbooks.ibm.com/abstracts/sg245674.html?Open
http://www.redbooks.ibm.com/redbooks/pdfs/sg245674.pdf
--
Seneca Cunningham
[EMAIL PROTECTED]
diff -wu postgresql-8.1.0.orig/configure postgresql-8.1.0/configure
--- postgresql-8.1.0.orig/configure 2005-11-04 23:01:38.0 -0500
+++ postgresql-8.1.0/configure 2005-11-21 12:47:28.0 -0500
@@ -998,7 +998,7 @@
else
echo "$as_me: WARNING: no configuration information is in $ac_dir" >&2
fi
-cd $ac_popdir
+cd "$ac_popdir"
done
fi
@@ -6498,7 +6498,7 @@
else
pgac_cv_check_readline=no
pgac_save_LIBS=$LIBS
-for pgac_rllib in -lreadline -ledit ; do
+for pgac_rllib in -ledit -lreadline ; do
for pgac_lib in "" " -ltermcap" " -lncurses" " -lcurses" ; do
LIBS="${pgac_rllib}${pgac_lib} $pgac_save_LIBS"
cat >conftest.$ac_ext <<_ACEOF
@@ -9646,6 +9646,152 @@
else
+for ac_header in histedit.h
+do
+as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+ echo "$as_me:$LINENO: checking for $ac_header" >&5
+echo $ECHO_N "checking for $ac_header... $ECHO_C" >&6
+if eval "test \"\${$as_ac_Header+set}\" = set"; then
+ echo $ECHO_N "(cached) $ECHO_C" >&6
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_Header'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_Header'}'`" >&6
+else
+ # Is the header compilable?
+echo "$as_me:$LINENO: checking $ac_header usability" >&5
+echo $ECHO_N "checking $ac_header usability... $ECHO_C" >&6
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h. */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h. */
+$ac_includes_default
+#include <$ac_header>
+_ACEOF
+rm -f conftest.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+ (eval $ac_compile) 2>conftest.er1
+ ac_status=$?
+ grep -v '^ *+' conftest.er1 >conftest.err
+ rm -f conftest.er1
+ cat conftest.err >&5
+ echo "$as_me:$LINENO: \$? = $ac_status" >&5
+ (exit $ac_status); } &&
+ { ac_try='test -z
