Re: [dpdk-dev] [PATCH] eal: remove variable length array

[Thomas Monjalon <thomas@monjalon.net>]

20/12/2018 11:53, Mattias Rönnblom:
> On 2018-12-19 22:45, Thomas Monjalon wrote:
> > 14/12/2018 21:28, Mattias Rönnblom:
> >> On 2018-12-14 20:07, Jeff Shaw wrote:
> >>>>> The code prior to this commit produced the following warning when
> >>>>> compiled with "-Wvla -std=c90".
> >>>>>
> >>>>>      warning: ISO C90 forbids variable length array ‘array’ [-Wvla]
> >>>>>
> >>>>> This commit removes the variable length array from the PMD debug
> >>>>> trace function by allocating memory dynamically on the stack using
> >>>>> alloca().
> >>>>
> >>>> Is alloca() even included in *any* C standard? As far as I see, it just
> >>>> achieves the same thing in an uglier, less portable way than VLAs.
> >>>
> >>> I agree that it is much less elegant than a VLA. This is in preparation
> >>> for DPDK on Windows, which using the Microsoft Visual C++ (MSVC) compiler.
> >>> MSVC does not support variable length arrays. It does, however, support
> >>> alloca(), as does GCC/ICC.
> >>>
> >>> For this particular instance, the point is moot, since the function is
> >>> not used anywhere and can just as easily be removed. Though it does not
> >>> address the issue for the ~100 other instances where VLAs are used. We
> >>> will be submitting patches for those as more common files are ported to
> >>> Windows.
> >>
> >> If Microsoft's C compiler doesn't support C99, some 20 years after its
> >> release, maybe it's time to find a new compiler, instead of messing up
> >> the DPDK code in a ~100 instances.
> > 
> > If think there is no reasonnable compiler for Windows.
> > Yes I know, it's crazy.
> > 
> With's wrong with the Windows version of Clang?

I agree it should be the preferred compiler for DPDK on Windows.

But Microsoft told there are some issues working with clang.
Jason, Harini, please, could you elaborate?