[clang] [-Wunsafe-buffer-usage] Add fixits for array to pointer assignment (PR #81343)

[Artem Dergachev via cfe-commits]

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@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -std=c++20 -Wunsafe-buffer-usage \
+// RUN:            -fsafe-buffer-usage-suggestions \
+// RUN:            -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+void safe_array_assigned_to_safe_ptr(unsigned idx) {
+  int buffer[10];
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+  int* ptr;
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+  ptr = buffer;
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+}
+
+void safe_array_assigned_to_unsafe_ptr(unsigned idx) {
+  int buffer[10];
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+  int* ptr;
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:11}:"std::span<int> ptr"
+  ptr = buffer;
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+  ptr[idx] = 0;
+}
+
+void unsafe_array_assigned_to_safe_ptr(unsigned idx) {
+  int buffer[10];
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:3-[[@LINE-1]]:17}:"std::array<int, 10> buffer"
+  int* ptr;
+  // CHECK-NOT: fix-it:"{{.*}}":{[[@LINE-1]]:
+  ptr = buffer;
+  // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:15-[[@LINE-1]]:15}:".data()"
+  buffer[idx] = 0;
+}
+
+void unsafe_array_assigned_to_unsafe_ptr(unsigned idx) {
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haoNoQ wrote:

Similarly, let's mark this test as a FIXME test, and add a comment explaining why this is hard and the naive fix would be incorrect.

https://github.com/llvm/llvm-project/pull/81343