Re: [Playerstage-developers] HAVE_LIBLTDL

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Well, it's just Linux, what else can I say? Also I've read in the manual 
that -ldl must be added whenever dlopen() is used. It's a guess game if 
current libtool-ltdl implementation is built on dlopen() or not (therefore 
it may need -ldl or not). Here I'm using libtool-1.5.6 and as we can see 
it uses -ldl. I know it's ancient version, but I couldn't compile anything 
newer for this crosscompilation environment.

Paul

On Mon, 25 Aug 2008, Geoffrey Biggs wrote:

> That's going to be fun to identify for special build options... Is there
> anything else unique about the system?
>
> Geoff
>
> Paul Osmialowski wrote:
>> Indeed, this helped alot as HAVE_LIBLTDL now is defined and set to 1.
>>
>> The system is very customly made cross-compilation environment for
>> embedded Linux running on cris/axis CPU (for my Roomba robots). It is
>> running on somewhat ancient Linux Fedora Core 3 with cmake 2.6.0 built
>> from tarball. The gcc cross-compiler is:
>> gcc (GCC) 3.2.1 Axis release R64/1.64
>> Copyright (C) 2002 Free Software Foundation, Inc.
>> This is free software; see the source for copying conditions.  There is NO
>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
>> PURPOSE.
>>
>> Paul
>>
>> On Mon, 25 Aug 2008, gbiggs wrote:
>>
>>> Try adding this line just before the check on line 44 in
>>> SearchForStuff.cmake:
>>>
>>> SET (CMAKE_REQUIRED_LIBRARIES dl)
>>>
>>> And just after the check, this line:
>>>
>>> SET (CMAKE_REQUIRED_LIBRARIES)
>>>
>>> See if that makes a difference. What system is this for, by the way?
>>>
>>> Geoff
>>>
>>>
>>> Paul Osmialowski wrote:
>>>> Hi Geoff
>>>>
>>>> I couldn't find anything about ltdl in CMakeFiles/CMakeOutput.log but I
>>>> didn't gave up with searching: I've found something like this in other
>>>> file, CMakeFiles/CMakeError.log:
>>>>
>>>> Determining if the function lt_dlopenext exists in the ltdl failed with
>>>> the following output:
>>>> Change Dir: /root/foxcross/build/CMakeFiles/CMakeTmp
>>>>
>>>> Run Build Command:/usr/bin/gmake "cmTryCompileExec/fast"
>>>> /usr/bin/gmake -f CMakeFiles/cmTryCompileExec.dir/build.make
>>>> CMakeFiles/cmTryCompileExec.dir/build
>>>>
>>>> gmake[1]: Entering directory `/root/foxcross/build/CMakeFiles/CMakeTmp'
>>>> /usr/local/bin/cmake -E cmake_progress_report
>>>> /root/foxcross/build/CMakeFiles/CMakeTmp/CMakeFiles 1
>>>>
>>>> Building C object CMakeFiles/cmTryCompileExec.dir/CheckFunctionExists.c.o
>>>> /usr/local/cris/cris-axis-linux-gnu/bin/gcc   -fPIC -isystem
>>>> /usr/local/cris/etrax/sys-include -I/mnt/flash/usr/include
>>>> -DCHECK_FUNCTION_EXISTS=lt_dlopenext   -o
>>>> CMakeFiles/cmTryCompileExec.dir/CheckFunctionExists.c.o   -c
>>>> /usr/local/share/cmake-2.6/Modules/CheckFunctionExists.c
>>>>
>>>> Linking C executable cmTryCompileExec
>>>> /usr/local/bin/cmake -E cmake_link_script
>>>> CMakeFiles/cmTryCompileExec.dir/link.txt --verbose=1
>>>> /usr/local/cris/cris-axis-linux-gnu/bin/gcc   -fPIC -isystem
>>>> /usr/local/cris/etrax/sys-include -I/mnt/flash/usr/include
>>>> -DCHECK_FUNCTION_EXISTS=lt_dlopenext  -fPIC -L/mnt/flash/usr/lib
>>>> -lltdl CMakeFiles/cmTryCompileExec.dir/CheckFunctionExists.c.o  -o
>>>> cmTryCompileExec -rdynamic -lltdl
>>>> /mnt/flash/usr/lib/libltdl.a(ltdl.o): In function `sys_dl_open':
>>>> ltdl.o(.text+0x626): undefined reference to `dlopen'
>>>> /usr/local/cris/lib/gcc-lib/cris-axis-linux-gnu/3.2.1/../../../../cris-axis-linux-gnu/bin/ld:
>>>> /mnt/flash/usr/lib/libltdl.a(ltdl.o): No PLT for relocation R_CRIS_32_GOTPLT against symbol
>>>> `dlopen' from .text section
>>>> /usr/local/cris/lib/gcc-lib/cris-axis-linux-gnu/3.2.1/../../../../cris-axis-linux-gnu/bin/ld:
>>>> final link failed: Bad value
>>>> collect2: ld returned 1 exit status
>>>> gmake[1]: *** [cmTryCompileExec] Error 1
>>>> gmake[1]: Leaving directory `/root/foxcross/build/CMakeFiles/CMakeTmp'
>>>> gmake: *** [cmTryCompileExec/fast] Error 2
>>>>
>>>> It is strange, as there's no problem with finding dlopen() while normal
>>>> building process... I guess this should be linked with -ldl flag.
>>>>
>>>> Also I noticed that this PLT relocation error pops up all the
>>>> (linking) time during building process but it does not cause linking
>>>> failure at the end.
>>>>
>>>> Cheers,
>>>> Paul
>>>>
>>>> On Mon, 25 Aug 2008, gbiggs wrote:
>>>>
>>>>> There are a couple of reasons why this check might fail:
>>>>>
>>>>> - The function "lt_dlopenext" doesn't exist in the file libltdl.a (seems
>>>>> unlikely if Player compiles fine, since Player uses this funciton).
>>>>> - Something extra needs to be linked when linking to libltdl.a which the
>>>>> check is missing but the Player build is including.
>>>>>
>>>>> Have a look in CMakeFiles/CMakeOutput.log under your build directory and
>>>>> find the section about ltdl, and paste it here. This will tell us
>>>>> exactly why the check failed.
>>>>>
>>>>> Geoff
>>>>>
>>>>> Paul Osmialowski wrote:
>>>>>> Hi Geoff,
>>>>>>
>>>>>> Can you say in what circumstances this may fail to find libltdl.a?:
>>>>>> CHECK_LIBRARY_EXISTS (ltdl lt_dlopenext "${PLAYER_EXTRA_LIB_DIRS}"
>>>>>> HAVE_LIBLTDL)
>>>>>>
>>>>>> This libltdl.a library is placed in some directory tree, CFLAGS and
>>>>>> CXXFLAGS points to include directory in that tree (-I), LIBS and LDFLAGS
>>>>>> points to lib directory in that tree (-L). I have also libjpeg and zlib
>>>>>> there (both static as .a files), and both are found by cmake properly,
>>>>>> while libtool-ltdl isn't! Mystery, isn't it?
>>>>>>
>>>>>> I'd changed generated playerconfig.h file manually whit #define
>>>>>> HAVE_LIBLTDL 1, and Player was built properly, also it was able to load
>>>>>> and execute .so plugins. What bothers cmake then?
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>>
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>
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