[cfe-commits] [PATCH] Make -Wvla warn in C99 mode (impact on -Wgnu?)

[Eli Friedman]

Patch attached; I would just commit, but it changes the behavior of
-Wgnu in a way I'm not sure is correct.  Can someone explain the
intent for -Wgnu and why it includes -Wvla?  (The svn history only
says it's supposed to "Control warnings about GNU extensions".)

-Eli
-------------- next part --------------
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td	(revision 129282)
+++ include/clang/Basic/DiagnosticSemaKinds.td	(working copy)
@@ -37,6 +37,9 @@
 def ext_vla : Extension<
   "variable length arrays are a C99 feature, accepted as an extension">,
   InGroup<VLA>;
+def warn_vla : Warning<
+  "variable length array used">,
+  InGroup<VLA>, DefaultIgnore;
 def err_vla_non_pod : Error<"variable length array of non-POD element type %0">;
 def err_vla_in_sfinae : Error<
   "variable length array cannot be formed during template argument deduction">;
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp	(revision 129282)
+++ lib/Sema/SemaType.cpp	(working copy)
@@ -1221,8 +1221,8 @@
     
     T = Context.getConstantArrayType(T, ConstVal, ASM, Quals);
   }
-  // If this is not C99, extwarn about VLA's and C99 array size modifiers.
   if (!getLangOptions().C99) {
+    // If this is not C99, extwarn about VLA's and C99 array size modifiers.
     if (T->isVariableArrayType()) {
       // Prohibit the use of non-POD types in VLAs.
       if (!T->isDependentType() && 
@@ -1243,6 +1243,10 @@
       Diag(Loc, 
            getLangOptions().CPlusPlus? diag::err_c99_array_usage_cxx
                                      : diag::ext_c99_array_usage);
+  } else {
+    // Warn about VLAs if the user uses -Wvla.
+    if (T->isVariableArrayType())
+      Diag(Loc, diag::warn_vla);
   }
 
   return T;