[clang-tidy] Add new check cppcoreguidelines-pro-bounds-array-to-pointer-decay

Summary:
This check flags all array to pointer decays.

Pointers should not be used as arrays. array_view is a bounds-checked,
safe alternative to using pointers to access arrays.

This rule is part of the "Bounds safety" profile of the C++ Core
Guidelines, see
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-bounds3-no-array-to-pointer-decay

Reviewers: alexfh, sbenza, bkramer, aaron.ballman

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D13640

llvm-svn: 251358

1 files changed, 41 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp
new file mode 100644
index 00000000000..13fd8a22142
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp
@@ -0,0 +1,41 @@
+// RUN: %check_clang_tidy %s cppcoreguidelines-pro-bounds-array-to-pointer-decay %t
+#include <stddef.h>
+
+namespace gsl {
+template <class T>
+class array_view {
+public:
+  template <class U, size_t N>
+  array_view(U (&arr)[N]);
+};
+}
+
+void pointerfun(int *p);
+void arrayfun(int p[]);
+void arrayviewfun(gsl::array_view<int> &p);
+size_t s();
+
+void f() {
+  int a[5];
+  pointerfun(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
+  pointerfun((int *)a); // OK, explicit cast
+  arrayfun(a);
+  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: do not implicitly decay an array into a pointer
+
+  pointerfun(a + s() - 10); // Convert to &a[g() - 10];
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: do not implicitly decay an array into a pointer
+
+  gsl::array_view<int> av(a);
+  arrayviewfun(av); // OK
+
+  int i = a[0];      // OK
+  pointerfun(&a[0]); // OK
+
+  for (auto &e : a) // OK, iteration internally decays array to pointer
+    e = 1;
+}
+
+const char *g() {
+  return "clang"; // OK, decay string literal to pointer
+}