[$] Variable-length arrays and the max() mess

Variable-length arrays (VLAs) have a non-constant size that is determined (andwhich can vary) at run time; they are supported by the ISO C99standard. Use of VLAs in thekernel has long been discouraged but not prohibited, so there are naturallynumerous VLA instances to be found. A recent push to remove VLAs from thekernel entirely has gained momentum, but it ran into an interesting snag onthe way.