[PATCH] D137343: [clang] add -Wvla-stack-allocation

[Tao Liang via Phabricator via cfe-commits]

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New behaviors:

`-Wvla`: produces portability warning for all VLAs like before
`-Wvla-portability`: not exists (equal to `-Wvla`)
`-Wvla-stack-allocation -Wno-vla`: only warns for VLAs that need stack allocation
`-Wvla -Wvla-stack-allocation`: warn for VLAs that need stack allocation, and give portablility warnings for other VLAs

Note that only one warning can be produced by one VLA because of
implementation complexity. Currently, VLAs are detected in
`BuildArrayType`, which will be used both by Parser and Tree Transformer.
And it passes the VLA-related warnings as an argument to other
functions. Producing multiple warnings for one VLA needs to change many
functions.

Fixes: https://github.com/llvm/llvm-project/issues/57098
Link: https://reviews.llvm.org/D132952

Co-authored-by: YingChi Long <me at inclyc.cn>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137343

Files:
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaType.cpp
  clang/test/Sema/warn-vla.c

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