[FFmpeg-devel] [PATCH 1/5] w32pthreads: always use Vista+ API, drop XP support

[James Almer]

On 12/21/2017 10:49 PM, wm4 wrote:
> On Thu, 21 Dec 2017 22:05:11 -0300
> James Almer <jamrial at gmail.com> wrote:
> 
>> On 12/21/2017 9:40 PM, wm4 wrote:
>>> On Thu, 21 Dec 2017 21:31:37 -0300
>>> James Almer <jamrial at gmail.com> wrote:
>>>   
>>>> On 12/21/2017 7:22 PM, wm4 wrote:  
>>>>> This removes the XP compatibility code, and switches entirely to SWR
>>>>> locks, which are available starting at Windows Vista.
>>>>>
>>>>> This removes CRITICAL_SECTION use, which allows us to add
>>>>> PTHREAD_MUTEX_INITIALIZER, which will be useful later.
>>>>>
>>>>> Windows XP is hereby not a supported build target anymore. It was
>>>>> decided in a project vote that this is OK. (Technically, it could still
>>>>> be built for Windows XP using an external pthread lib as of this
>>>>> commit.)
>>>>>
>>>>> Windows Vista adds WSAPoll(), and for some reason struct pollfd. Since
>>>>> we raise the Windows API level globally when enabling w32threads, we
>>>>> need to move it before configure checks for struct pollfd to avoid that
>>>>> the compatibility ifdef mess redefines it.
>>>>> ---
>>>>> Not sure if there's a better way to do the things configure does.
>>>>> ---
>>>>>  Changelog                  |   2 +
>>>>>  compat/w32pthreads.h       | 269 ++-------------------------------------------
>>>>>  configure                  |  93 ++++++++--------
>>>>>  libavcodec/pthread_frame.c |   4 -
>>>>>  libavcodec/pthread_slice.c |   4 -
>>>>>  libavfilter/pthread.c      |   4 -
>>>>>  libavutil/slicethread.c    |   4 -
>>>>>  7 files changed, 60 insertions(+), 320 deletions(-)    
>>>>
>>>> [...]
>>>>  
>>>>> --- a/configure
>>>>> +++ b/configure
>>>>> @@ -2089,7 +2089,6 @@ TOOLCHAIN_FEATURES="
>>>>>  "
>>>>>  
>>>>>  TYPES_LIST="
>>>>> -    CONDITION_VARIABLE_Ptr
>>>>>      kCMVideoCodecType_HEVC
>>>>>      socklen_t
>>>>>      struct_addrinfo
>>>>> @@ -5163,8 +5162,8 @@ probe_libc(){
>>>>>          add_${pfx}cppflags -U__STRICT_ANSI__ -D__USE_MINGW_ANSI_STDIO=1
>>>>>          check_${pfx}cpp_condition _mingw.h "__MSVCRT_VERSION__ < 0x0700" &&
>>>>>              add_${pfx}cppflags -D__MSVCRT_VERSION__=0x0700
>>>>> -        check_${pfx}cpp_condition windows.h "defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0502" &&
>>>>> -            add_${pfx}cppflags -D_WIN32_WINNT=0x0502
>>>>> +        check_${pfx}cpp_condition windows.h "defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0600" &&
>>>>> +            add_${pfx}cppflags -D_WIN32_WINNT=0x0600    
>>>>
>>>> This same check should now also be added to the mingw-w64 part of this
>>>> function.
>>>> Until now, this was done this way because mingw32 defaults to Win98,
>>>> whereas mingw-w64 to WinXP. Now we need Vista in both.  
>>>
>>> Oh, I didn't even notice that was mingw32 only.
>>>   
>>>> It would be a good idea for that matter to make sure all the required
>>>> Vista API is actually supported by Mingw32 3.15, or if we need to bump
>>>> that (or just drop mingw32 support, which wouldn't really hurt).  
>>>
>>> The code already checks for CONDITION_VARIABLE. Any other things I
>>> should check for? Maybe a representative function? (I don't think I'm
>>> going to add checks for _all_ the symbols.)  
>>
>> Didn't realize that was checked, so no, should be good then.
>>
>>>   
>>>>>          eval test \$${pfx_no_}cc_type = "gcc" &&
>>>>>              add_${pfx}cppflags -D__printf__=__gnu_printf__
>>>>>      elif check_${pfx}cpp_condition crtversion.h "defined _VC_CRT_MAJOR_VERSION"; then
>>>>> @@ -5184,14 +5183,14 @@ probe_libc(){
>>>>>          # 0x601 by default unless something else is set by the user.
>>>>>          # This can easily lead to us detecting functions only present
>>>>>          # in such new versions and producing binaries requiring windows 7.0.
>>>>> -        # Therefore explicitly set the default to XP unless the user has
>>>>> +        # Therefore explicitly set the default to Vista unless the user has
>>>>>          # set something else on the command line.
>>>>>          # Don't do this if WINAPI_FAMILY is set and is set to a non-desktop
>>>>>          # family. For these cases, configure is free to use any functions
>>>>>          # found in the SDK headers by default. (Alternatively, we could force
>>>>>          # _WIN32_WINNT to 0x0602 in that case.)
>>>>>          check_${pfx}cpp_condition stdlib.h "defined(_WIN32_WINNT)" ||
>>>>> -            { check_${pfx}cpp <<EOF && add_${pfx}cppflags -D_WIN32_WINNT=0x0502; }
>>>>> +            { check_${pfx}cpp <<EOF && add_${pfx}cppflags -D_WIN32_WINNT=0x0600; }
>>>>>  #ifdef WINAPI_FAMILY
>>>>>  #include <winapifamily.h>
>>>>>  #if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
>>>>> @@ -5564,6 +5563,51 @@ check_code cc arm_neon.h "int16x8_t test = vdupq_n_s16(0)" && enable intrinsics_
>>>>>  check_ldflags -Wl,--as-needed
>>>>>  check_ldflags -Wl,-z,noexecstack
>>>>>  
>>>>> +if ! disabled w32threads && ! enabled pthreads; then
>>>>> +    check_func_headers "windows.h process.h" _beginthreadex &&
>>>>> +        check_type "windows.h" CONDITION_VARIABLE &&
>>>>> +        enable w32threads || disable w32threads
>>>>> +    if ! enabled w32threads && enabled winrt; then
>>>>> +        check_func_headers "windows.h" CreateThread &&
>>>>> +            enable w32threads || disable w32threads
>>>>> +    fi
>>>>> +fi
>>>>> +
>>>>> +if enabled w32threads; then
>>>>> +    if check_cpp_condition windows.h "!defined(_WIN32_WINNT) || _WIN32_WINNT < 0x0600" ; then
>>>>> +        add_cppflags -D_WIN32_WINNT=0x0600    
>>>>
>>>> Win Vista should be forced regardless of w32threads being enabled or
>>>> not, so this should be done in probe_libc().  
>>>
>>> OK, sounds good. So this means we always set _WIN32_WINNT
>>> unconditionally (unless it's already set to something higher than
>>> Vista). This will probably simplify the configure changes.  
>>
>> Yes, that's the idea. After this we should also remove the lavf
>> os_support compat code (things like poll emulation).
> 
> I don't think Windows provides poll(). I don't know why the winsock
> headers contain a pollfd struct. WSAPoll(), which supposedly works like
> poll(), is not poll(), and also was rejected by the libcurl devs:
> 
> https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/

I meant the pollfd struct, sorry. We'd not need to compat definition for
it anymore.