[vlc-devel] [RFC] fix multiple definition of `inet_pton' when including microdns.h on WIN32

[Steve Lhomme]

On 2019-07-19 12:37, Roland Bewick wrote:
> 
> On 19/07/2019 5:12 PM, Steve Lhomme wrote:
>> On 2019-07-19 12:07, Roland Bewick wrote:
>>> Hi Steve, thanks for your reply.
>>>
>>> On 19/07/2019 2:53 PM, Steve Lhomme wrote:
>>>> Hi,
>>>>
>>>> On 2019-07-19 6:04, Roland Bewick wrote:
>>>>>
>>>>> Hi, I'm looking to use the inet_pton function within 
>>>>> modules\services_discovery\microdns.c
>>>>>
>>>>> Unfortunately it looks to be defined twice when I cross compile for 
>>>>> Windows:
>>>>>
>>>>> 1. in libmicrodns (compat/inet.c) - will only be declared if 
>>>>> defined (_WIN32) && !defined(HAVE_INET_NTOP)
>>>>
>>>> On my win32 cross compilation (clang + mingw32) HAVE_INET_NTOP is 
>>>> set to 1 so this code is never compiled.
>>>>
>>>>> 2. in libws2_32.a (I think from including winsock2.h?)
>>>>>
>>>>> /opt/gcc-x86_64-w64-mingw32/x86_64-w64-mingw32/lib/libws2_32.a(dywbs00169.o):(.text+0x0): 
>>>>> multiple definition of `inet_pton'
>>>>> /win64/vlc/contrib/x86_64-w64-mingw32/lib/libmicrodns.a(inet.o):/win64/libmicrodns/build/../compat/inet.c:60: 
>>>>> first defined here
>>>>
>>>> When building VLC with the same configuration HAVE_INET_PTON is set 
>>>> and thus the compat function is never built either. The ws2_32 one 
>>>> is used.
>>>>
>>>> So it seems rather an issue in your toolchain/build script. Are you 
>>>> using MSVC ? The 3.0 branch ?
>>>
>>>
>>> I followed this docker guide:
>>>
>>> https://gitlab.com/garfvl/daalenv/blob/master/doc/vlc.md for win64 
>>> with prebuilt contribs (tip #2 in the readme).
>>>
>>> I’m not using MSVC.
>>>
>>> I’m on the master branch.
>>>
>>> Since I'm using the prebuilt libs and standard? build script for 
>>> win64, I'm worried other people might encounter this as well.
>>
>> Maybe the docker uses an outdated version on mingw32 ? It seems very 
>> odd that `inet_pton` is defined in ws2_32 but not found in the headers.
>>
>> Can you check your config.log to see what it says when checking for it ?
> 
> It looks like it's failing so HAVE_INET_PTON is not being set as expected.
> 
>  From line 13814:
> 
> configure:25828: checking for library containing inet_pton
> configure:25859: x86_64-w64-mingw32-gcc -o conftest.exe -g -O2 
> -I/win64/vlc/contrib/x86_64-w64-mingw32/include -mms-bitfields 
> -I/win64/vlc/contrib/x86_64-w64-mingw32/include 
> -D__USE_MINGW_ANSI_STDIO=1  -Wl,--nxcompat -Wl,--no-seh 
> -Wl,--dynamicbase -Wl,--high-entropy-va -Wl,--image-base,0x140000000 
> -L/win64/vlc/contrib/x86_64-w64-mingw32/lib conftest.c  >&5
> /tmp/ccT0CMSB.o: In function `main':
> /win64/vlc/win64/conftest.c:89: undefined reference to `inet_pton'
> /win64/vlc/win64/conftest.c:89:(.text.startup+0xa): relocation truncated 
> to fit: R_X86_64_PC32 against undefined symbol `inet_pton'
> collect2: error: ld returned 1 exit status
> configure:25859: $? = 1
> configure: failed program was:
> 
> ...
> 
> If needed, you can see the full config file below (1MB)
> 
> https://www.dropbox.com/s/m2rklvzyl1lkst6/config.log?dl=0

Yes, there are many different checks but in the end it is found.
You can see HAVE_INET_PTON is set to 1 afterwards up to the end of the 
script. So it should be set to that value in config.h as well.

>>
>>>>
>>>>> I've commented out the contents of the compat/inet.c file and 
>>>>> successfully VLC with the modified libmicrodns.
>>>>>
>>>>> Is it ok to add a patch to contrib\src\microdns (see example 
>>>>> below), or is there a better way? Is it because it's linking 
>>>>> libmicrodns before//libws2_32 rather than after?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Roland
>>>>>
>>>>>
>>>>>  From e364a3201b30e88236dd62c892e9cb24e9c36fb2 Mon Sep 17 00:00:00 
>>>>> 2001
>>>>> From: Roland Bewick <roland.bewick at gmail.com>
>>>>> Date: Thu, 18 Jul 2019 11:55:59 +0700
>>>>> Subject: [PATCH] remove unneeded inet compatibility
>>>>>
>>>>> ---
>>>>>   compat/inet.c | 4 ++--
>>>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/compat/inet.c b/compat/inet.c
>>>>> index 2983e4d..9c2dfb8 100644
>>>>> --- a/compat/inet.c
>>>>> +++ b/compat/inet.c
>>>>> @@ -27,7 +27,7 @@
>>>>>   #include "compat.h"
>>>>>   #include "utils.h"
>>>>>
>>>>> -#if defined (_WIN32) && !defined(HAVE_INET_NTOP)
>>>>> +/*#if defined (_WIN32) && !defined(HAVE_INET_NTOP)
>>>>>   const char *
>>>>>   inet_ntop(int af, const void *src, char *dst, socklen_t size)
>>>>>   {
>>>>> @@ -67,4 +67,4 @@ int inet_pton (int af, const char *src, void *dst)
>>>>>       errno = EAFNOSUPPORT;
>>>>>       return -1;
>>>>>   }
>>>>> -#endif // _WIN32 && !inet_ntop
>>>>> +#endif // _WIN32 && !inet_ntop */
>>>>> -- 
>>>>> 2.17.1
>>>>>
>>>>>
>>>>>
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