Implement -Wvla correctly

GCC implements -Wvla as "warn on every VLA" (this is useful to find every VLA,
for example, if they are forbidden by coding guidelines).  Currently Clang
implements -Wvla as "warn on VLA when it is an extension".

The attached patch makes our behavior match GCC.  The existing vla extwarn is
moved under -Wvla-extension and is still included into -Wgnu.

This fixes PR5953.

llvm-svn: 173286

1 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index dbee50a4c93..f6cad26989c 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1496,6 +1496,11 @@ QualType Sema::BuildArrayType(QualType T, ArrayType::ArraySizeModifier ASM,
                                      : diag::ext_c99_array_usage) << ASM;
   }
 
+  if (T->isVariableArrayType()) {
+    // Warn about VLAs for -Wvla.
+    Diag(Loc, diag::warn_vla_used);
+  }
+
   return T;
 }