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

["Mattias Rönnblom" <mattias.ronnblom@ericsson.com>]

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?