[PATCH 0/4] RFC samples converting VLA to alloca

[Tyler Retzlaff]

This series is not intended for merge.  It insteat provides examples of
converting use of VLAs to alloca() would look like.

what's the advantages of VLA over alloca()?

* sizeof(array) works as expected.

* multi-dimensional arrays are still arrays instead of pointers to
  dynamically allocated space. this means multiple subscript syntax
  works (unlike on a pointer) and calculation of addresses into allocated
  space in ascending order is performed by the compiler instead of manually.

what's the disadvantage of VLA over alloca()?

* VLA generation is subtl/implicit, there do appear to be places where
  a VLA is being used where it perhaps was not intended but it is hard
  to spot. e.g. hotpath rte_mbuf *array[burst_size]; where burst_size
  is not a constant expression, e.g. unintended in other syntax positions
  that are not intuitive, see patchwork link.

  https://patchwork.dpdk.org/project/dpdk/patch/1699896038-28106-1-git-send-email-roretzla@linux.microsoft.com/

for the above reasons i'd recommend only converting to alloca() where
necessary (msvc has to compile it) and for the other instances leave
them as they are.

Tyler Retzlaff (4):
  latencystats: use alloca instead of vla trivial
  hash: use alloca instead of vla trivial
  vhost: use alloca instead of vla sizeof
  dispatcher: use alloca instead of vla multi dimensional

 lib/dispatcher/rte_dispatcher.c     | 6 +++---
 lib/hash/rte_thash.c                | 2 +-
 lib/latencystats/rte_latencystats.c | 2 +-
 lib/vhost/socket.c                  | 5 +++--
 4 files changed, 8 insertions(+), 7 deletions(-)

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