Re: MinGW build of GDB 8.2.90

[Sergio Durigan Junior <sergiodj@redhat.com>]

On Thursday, February 28 2019, Eli Zaretskii wrote:

>> From: Joel Brobecker <brobecker@adacore.com>
>> Date: Wed, 27 Feb 2019 09:51:12 +0400 (+04)
>> 
>> I have just finished creating the gdb-8.2.90 pre-release.
>> It is available for download at the following location:
>> 
>>     ftp://sourceware.org/pub/gdb/snapshots/branch/gdb-8.2.90.tar.xz
>
> Thanks, I've built this with mingw.org's MinGW and bumped into a few
> problems.
>
> First, the recent changes to support IPv6 caused compilation errors in
> several files.  The problem is with several fragments such as this
> one:
>
>   #ifdef USE_WIN32API
>   #include <winsock2.h>
>   #include <wspiapi.h>
>   #else
>   ...
>
> mingw.org's MinGW doesn't have wspiapi.h.  Moreover, the Microsoft
> documentation indicates that to get prototypes of getaddrinfo,
> freeaddrinfo, etc. one needs to include ws2tcpip.h (and not include
> winsock2.h separately), see, for example,
>
>   https://docs.microsoft.com/en-us/windows/desktop/api/ws2tcpip/nf-ws2tcpip-getaddrinfo
>
> Sergio, can you tell why you used wspiapi.h instead?

Thanks for the report, Eli.

To be honest, I don't remember where I found the information that
wspiapi.h needed to be used, but I do remember finding it somewhere on
the internet, and since I don't use Windows, I assumed it was correct.

However, and more importantly, I remember testing the whole patch by
compiling it using a mingw32 compiler on Fedora, and it was working
correctly.  In fact, we even have a mingw32 builder on our BuildBot
(running on Fedora), and it is still compiling GDB without problems:

  https://gdb-build.sergiodj.net/builders/Fedora-x86_64-w64-mingw32

So apparently this error is only triggered when you use mingw on
Windows...?  I don't know.

> Is it okay to push changes such as the one below, master and branch
> (after filing a Bugzilla report)?
>
> --- ./gdb/common/netstuff.c~0	2019-02-27 06:51:50.000000000 +0200
> +++ ./gdb/common/netstuff.c	2019-02-28 08:56:07.511568800 +0200
> @@ -21,8 +21,11 @@
>  #include <algorithm>
>  
>  #ifdef USE_WIN32API
> -#include <winsock2.h>
> -#include <wspiapi.h>
> +#if _WIN32_WINNT < 0x0501
> +# undef _WIN32_WINNT
> +# define _WIN32_WINNT 0x0501
> +#endif
> +#include <ws2tcpip.h>
>  #else
>  #include <netinet/in.h>
>  #include <arpa/inet.h>

As I said, I don't use Windows and don't understand the system, but if
these changes fix the problem for you, I'd say they're justified and
should be pushed (even though I don't understand the "if
_WIN32_WINNT..." part).

> Note that one other side effect of the IPv6 support additions is that
> on MS-Windows GDB will no longer run on versions older than XP, I
> guess this is something that should be mentioned in NEWS?

I confess I did not know that.  If that's the case, then we should
indeed notify the users via the NEWS file, IMO.

> The other two problems were minor warning, one in tui.c about an
> unused variable 'cap' (it is not used on Windows) and another in
> xml-syscall.c:
>
>        CXX    xml-syscall.o
>      xml-syscall.c: In function 'bool xml_list_syscalls_by_group(gdbarch*, const char*, std::vector<int>*)':
>      xml-syscall.c:475:14: warning: types may not be defined in a for-range-declaration
> 	for (const struct syscall_desc *sysdesc : groupdesc->syscalls)
> 		   ^~~~~~
>
> I solved the latter by removing "struct" from the declaration.  This
> is with GCC 6.3.0; is that a GCC bug? is removing "struct" the right
> solution?

Yeah, this is the right thing to do.  I remember having to do this a few
times, and seeing other patches doing the same.

Thanks,

-- 
Sergio
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