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

Mattias Rönnblom mattias.ronnblom at ericsson.com
Fri Dec 14 21:28:05 CET 2018

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.

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