Re: [PATCH] Fix libtool.m4 dlopen lookup for mingw

[Pavel Chupin <pavel.v.chupin@gmail.com>]

On Tue, Nov 27, 2012 at 12:16 PM, Kai Tietz <ktietz70@googlemail.com> wrote:
> 2012/11/27 Joel Brobecker <brobecker@adacore.com>:
>> Hi Pavel,
>>
>>> Attached patch removes mingw from special cases of dlopen lookup. It
>>> allows dlopen to be found later in libdl and have it added properly as
>>> -ldl in bfd and sim builds.
>>>
>>> To reproduce the problem:
>>>
>>> ../configure --enable-plugins --target=arm-linux-android
>>> --host=i586-pc-mingw32msvc --build=i386-linux-gnu
>>> make
>>>
>>> Error:
>>> ../../bfd/libbfd.a(plugin.o): In function `try_load_plugin':
>>> /tmp/gdb/BUILD/bfd/../../bfd/plugin.c:170: undefined reference to `dlopen'
>>> /tmp/gdb/BUILD/bfd/../../bfd/plugin.c:177: undefined reference to `dlsym'
>>> /tmp/gdb/BUILD/bfd/../../bfd/plugin.c:173: undefined reference to `dlerror'
>>>
>>> ChangeLog:
>>>
>>> 2012-11-27  Pavel Chupin  <pavel.v.chupin@intel.com>
>>>
>>>         Fix libtool.m4 libdl lookup for mingw
>>>         * libtool.m4: Remove mingw from special case of dlopen lookup
>>>         * bfd/configure: Regenerate.
>>>         * sim/arm/configure: Regenerate.
>>>         * sim/avr/configure: Regenerate.
>>>         * sim/bfin/configure: Regenerate.
>>>         * sim/common/configure: Regenerate.
>>>         * sim/cr16/configure: Regenerate.
>>>         * sim/cris/configure: Regenerate.
>>>         * sim/d10v/configure: Regenerate.
>>>         * sim/erc32/configure: Regenerate.
>>>         * sim/frv/configure: Regenerate.
>>>         * sim/h8300/configure: Regenerate.
>>>         * sim/iq2000/configure: Regenerate.
>>>         * sim/lm32/configure: Regenerate.
>>>         * sim/m32c/configure: Regenerate.
>>>         * sim/m32r/configure: Regenerate.
>>>         * sim/m68hc11/configure: Regenerate.
>>>         * sim/mcore/configure: Regenerate.
>>>         * sim/microblaze/configure: Regenerate.
>>>         * sim/mips/configure: Regenerate.
>>>         * sim/mn10300/configure: Regenerate.
>>>         * sim/moxie/configure: Regenerate.
>>>         * sim/rl78/configure: Regenerate.
>>>         * sim/rx/configure: Regenerate.
>>>         * sim/sh/configure: Regenerate.
>>>         * sim/sh64/configure: Regenerate.
>>>         * sim/v850/configure: Regenerate.
>>
>> Thanks for sending this patch.
>>
>> Changes to the root directory are controled by the GCC developers,
>> so you will need to send your patch there for approval. But looking
>> at your patch, I am wondering whether it is actually right. I have
>> two reasons for questioning your patch:
>>
>>   - I don't think MinGW actually provides libdl, at least not by default.
>>     Your change would probably break the build for those who do not
>>     have the dlfcn extension installed;
>
> Right, by default there is no such library present.  Therefore mingw
> can't dependent on the presence of such a library.
>
>>   - Looking at bfd/plugin.c, there are implementations of these
>>     dlfcn functions provided by that file for Windows.
>>     These implementations are guarded by:
>>
>>         #if !defined (HAVE_DLFCN_H) && defined (HAVE_WINDOWS_H)
>>
>> I am guessing that your MinGW install has dlfcn.h. Perhaps the problem
>> would need to be fixed in bfd instead (binutils AT sourceware dot org).
>
> Yes, I assume that a fix of the issue you had should be addressed in
> binutils instead.
>
> Regards,
> Kai

Thanks for review. You are right. I've removed mingw-dlfcn on my
machine and dlopen is picked up from plugin.c so issue is gone. It
seems to fix both cases need to add check for dlfcn.h for mingw and if
present use dlopen from libdl, otherwise use LoadLibrary version.
Looks like libtool.m4 is the right place to do such sort of checks.
What do you think?

--
Pavel Chupin
Intel Corporation