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

[Roland Bewick]

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.


>
>> 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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