[Diagnostics] Implement -Wsizeof-pointer-div

Summary:
void test(int *arr) {
    int arr_len = sizeof(arr) / sizeof(*arr);  // warn, incorrect way to compute number of array elements
}

Enabled under -Wall (same behaviour as GCC)

Reviewers: rsmith, MTC, aaron.ballman

Reviewed By: aaron.ballman

Subscribers: MTC, thakis, jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D52949

llvm-svn: 345847

1 files changed, 28 insertions, 0 deletions

diff --git a/clang/test/Sema/div-sizeof-ptr.cpp b/clang/test/Sema/div-sizeof-ptr.cpp
new file mode 100644
index 00000000000..4a411ff6bb0
--- /dev/null
+++ b/clang/test/Sema/div-sizeof-ptr.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 %s -verify -Wsizeof-pointer-div -fsyntax-only
+
+template <typename Ty, int N>
+int f(Ty (&Array)[N]) {
+  return sizeof(Array) / sizeof(Ty); // Should not warn
+}
+
+void test(int *p, int **q) {
+  int a1 = sizeof(p) / sizeof(*p);   // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+  int a2 = sizeof p / sizeof *p;     // expected-warning {{'sizeof p' will return the size of the pointer, not the array itself}}
+  int a3 = sizeof(*q) / sizeof(**q); // expected-warning {{'sizeof (*q)' will return the size of the pointer, not the array itself}}
+  int a4 = sizeof(p) / sizeof(int);  // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+  int a5 = sizeof(p) / sizeof(p[0]); // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+
+  // Should not warn
+  int b1 = sizeof(int *) / sizeof(int);
+  int b2 = sizeof(p) / sizeof(p);
+  int b3 = sizeof(*q) / sizeof(q);
+  int b4 = sizeof(p) / sizeof(char);
+
+  int arr[10];
+  int b5 = sizeof(arr) / sizeof(*arr);
+  int b6 = sizeof(arr) / sizeof(arr[0]);
+  int b7 = sizeof(arr) / sizeof(int);
+
+  int arr2[10][12];
+  int b8 = sizeof(arr2) / sizeof(*arr2);
+}