[-Wunsafe-buffer-usage] Avoid multi-dimentional arrays properly

Array element can be for example VLA which given its non-constant length can't be transformed to std::array.

Author: jkorous-apple

clang/lib/Analysis/UnsafeBufferUsage.cpp

@@ -2481,7 +2481,7 @@ static FixItList fixVarDeclWithArray(const VarDecl *D, const ASTContext &Ctx,
     const QualType &ArrayEltT = CAT->getElementType();
     assert(!ArrayEltT.isNull() && "Trying to fix a non-array type variable!");
     // FIXME: support multi-dimensional arrays
-    if (isa<clang::ConstantArrayType>(ArrayEltT))
+    if (isa<clang::ArrayType>(ArrayEltT.getCanonicalType()))
       return {};
 
     const SourceLocation IdentifierLoc = getVarDeclIdentifierLoc(D);

clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-local-var-array.cpp

@@ -16,21 +16,36 @@ void array2d(unsigned idx) {
   buffer[idx][idx] = 0;
 }
 
+void array2d_vla(unsigned sz, unsigned idx) {
+  int buffer1[10][sz];
+// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
+  int buffer2[sz][10];
+// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
+  buffer1[idx][idx] = 0;
+  buffer2[idx][idx] = 0;
+}
+
 void array2d_assign_from_elem(unsigned idx) {
   int buffer[10][10];
 // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
   int a = buffer[idx][idx];
 }
 
-void array2d_use(unsigned);
+void array2d_use(int *);
 void array2d_call(unsigned idx) {
   int buffer[10][10];
 // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
-  array2d_use(buffer[idx][idx]);
+  array2d_use(buffer[idx]);
+}
+void array2d_call_vla(unsigned sz, unsigned idx) {
+  int buffer[10][sz];
+// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
+  array2d_use(buffer[idx]);
 }
 
 void array2d_typedef(unsigned idx) {
   typedef int ten_ints_t[10];
+// CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
   ten_ints_t buffer[10];
 // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]
   buffer[idx][idx] = 0;