[PATCH] D89523: PR44406: Follow behavior of array bound constant folding in more recent versions of GCC.

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith created this revision.
rsmith added a reviewer: eli.friedman.
Herald added a project: clang.
rsmith requested review of this revision.

Old GCC used to aggressively fold VLAs to constant-bound arrays at block
scope in GNU mode. That's non-conforming, and more modern versions of
GCC only do this at file scope. Update Clang to do the same.

Also promote the warning for this from off-by-default to on-by-default
in all cases; more recent versions of GCC likewise warn on this by
default.

This is still slightly more permissive than GCC, as pointed out in
PR44406, as we still fold VLAs to constant arrays in structs, but that
seems justifiable given that we don't support VLA-in-struct (and don't
intend to ever support it), but GCC does.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D89523

Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaDecl.cpp
  clang/lib/Sema/SemaType.cpp
  clang/test/CXX/basic/basic.types/p10.cpp
  clang/test/CXX/drs/dr3xx.cpp
  clang/test/CodeGen/vla.c
  clang/test/Misc/warning-flags.c
  clang/test/PCH/cxx-constexpr.cpp
  clang/test/Profile/misexpect-switch-default.c
  clang/test/Profile/misexpect-switch-nonconst.c
  clang/test/Profile/misexpect-switch-only-default-case.c
  clang/test/Profile/misexpect-switch.c
  clang/test/Sema/builtin-assume.c
  clang/test/Sema/builtins.c
  clang/test/Sema/complex-int.c
  clang/test/Sema/const-eval-64.c
  clang/test/Sema/const-eval.c
  clang/test/Sema/darwin-align-cast.c
  clang/test/Sema/decl-in-prototype.c
  clang/test/Sema/gnu-flags.c
  clang/test/Sema/i-c-e.c
  clang/test/Sema/offsetof-64.c
  clang/test/Sema/struct-decl.c
  clang/test/Sema/typedef-variable-type.c
  clang/test/Sema/vla.c
  clang/test/SemaCXX/anonymous-struct.cpp
  clang/test/SemaCXX/constant-expression.cpp
  clang/test/SemaCXX/cxx1z-noexcept-function-type.cpp
  clang/test/SemaCXX/i-c-e-cxx.cpp
  clang/test/SemaObjC/gcc-cast-ext.m

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