Re: [dpdk-dev] [PATCH 6/7] cmdline: support Windows

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

On Mon, 29 Jun 2020 08:12:51 +0000, Tal Shnaiderman wrote:
> > From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> > Subject: Re: [dpdk-dev] [PATCH 6/7] cmdline: support Windows
> > 
> > On Sun, 28 Jun 2020 23:23:11 -0700, Ranjit Menon wrote:  
> > > On 6/28/2020 7:20 AM, Fady Bader wrote:  
> > > > Hi Dmitry,
> > > > I'm trying to run test-pmd on Windows and I ran into this error with  
> > cmdline.  
> > > >
> > > > The error log message is :
> > > > In file included from ../app/test-pmd/cmdline_flow.c:23:
> > > > ..\lib\librte_cmdline/cmdline_parse_num.h:24:2: error: 'INT64'  
> > redeclared as different kind of symbol  
> > > >    INT64
> > > >
> > > > In file included from C:/mingw-w64/x86_64/mingw64/x86_64-w64-  
> > mingw32/include/winnt.h:150,  
> > > >                   from C:/mingw-w64/x86_64/mingw64/x86_64-w64-  
> > mingw32/include/minwindef.h:163,  
> > > >                   from C:/mingw-w64/x86_64/mingw64/x86_64-w64-  
> > mingw32/include/windef.h:8,  
> > > >                   from C:/mingw-w64/x86_64/mingw64/x86_64-w64-  
> > mingw32/include/windows.h:69,  
> > > >                   from ..\lib/librte_eal/windows/include/rte_windows.h:22,
> > > >                   from ..\lib/librte_eal/windows/include/pthread.h:20,
> > > >                   from ..\lib/librte_eal/include/rte_per_lcore.h:25,
> > > >                   from ..\lib/librte_eal/include/rte_errno.h:18,
> > > >                   from ..\lib\librte_ethdev/rte_ethdev.h:156,
> > > >                   from ../app/test-pmd/cmdline_flow.c:18:
> > > > C:/mingw-w64/x86_64/mingw64/x86_64-w64-  
> > mingw32/include/basetsd.h:32:44: note: previous declaration of 'INT64' was
> > here  
> > > >     __MINGW_EXTENSION typedef signed __int64 INT64,*PINT64;
> > > >
> > > > The same error is for the other types defined in cmdline_numtype.
> > > >
> > > > This problem with windows.h is popping in many places and some of
> > > > them are cmdline and test-pmd and librte_net.
> > > > We should find a way to exclude windows.h from the unneeded places,
> > > > is there any suggestions on how it can be done ?  
> > >
> > > We ran into this same issue when working with the code that is on the
> > > draft repo.
> > >
> > > The issue is that UINT8, UINT16, INT32, INT64 etc. are reserved types
> > > in Windows headers for integer types. We found that it is easier to
> > > change the enum in cmdline_parse_num.h than try to play with the
> > > include order of headers. AFAIK, the enums were only used to determine
> > > the type in a series of switch() statements in librte_cmdline, so we
> > > simply renamed the enums. Not sure, if that will be acceptable here.  
> > 
> > +1 for renaming enum values. It's not a problem of librte_cmdline itself
> > +but a
> > problem of its consumption on Windows, however renaming enum values
> > doesn't break ABI and winn make librte_cmdline API "namespaced".
> > 
> > I don't see a clean way not to expose windows.h, because pthread.h
> > depends on it, and if we hide implementation, librte_eal would have to
> > export pthread symbols on Windows, which is a hack (or is it?).  
> 
> test_pmd redefine BOOLEAN and PATTERN in the index enum, I'm not sure how many more conflicts we will face because of this huge include.
>
> Also, DPDK applications will inherit it unknowingly, not sure if this is common for windows libraries.

I never hit these particular conflicts, but you're right that there will be
more, e.g. I remember particularly nasty clashes in failsafe PMD, unrelated
to cmdline token names.


We could take the same approach as with networking headers: copy required
declarations instead of including them from SDK. Here's a list of what
pthread.h uses:

CloseHandle
CreateThread
DeleteSynchronizationBarrier
EnterSynchronizationBarrier
GetThreadAffinityMask
InitializeSynchronizationBarrier
OpenThread
SetPriorityClass
SetThreadAffinityMask
SetThreadPriority
TerminateThread

Windows has strict compatibility policy, so prototypes are unlikely to ever
change. None of the used functions takes string parameters, thus not affected
by A/W macros. Looks a bit messy, but it's limited in scope at least.


An external pthread library would solve the problem, but as I've reported
earlier, I failed to find a good one: [1] and [3] are tied to MinGW, although
of high quality, [2] seems outdated.

[1]: Wnpthreads:
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-libraries/winpthreads/
[2] pthreads-win32: https://sourceware.org/pthreads-win32/
[3] mcfgthread: https://github.com/lhmouse/mcfgthread

-- 
Dmitry Kozlyuk