[clang] [analyzer] Detect use-after-free for field address (e.g., &ptr->field) (PR #152462)

[Balazs Benics via cfe-commits]

================
@@ -0,0 +1,44 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc -verify %s
+
+#include "Inputs/system-header-simulator-for-malloc.h"
+
+struct Obj {
+  int field;
+};
+
+void use(void *ptr);
+
+void test_direct_param_uaf() {
+  int *p = (int *)malloc(sizeof(int));
+  free(p);
+  use(p); // expected-warning{{Use of memory after it is freed}}
+}
+
+void test_struct_field_uaf() {
+  struct Obj *o = (struct Obj *)malloc(sizeof(struct Obj));
+  free(o);
+  use(&o->field); // expected-warning{{Use of memory after it is freed}}
+}
+
+void test_no_warning_const_int() {
+  use((void *)0x1234); // no-warning
+}
+
+void test_no_warning_stack() {
+  int x = 42;
+  use(&x); // no-warning
+}
+
+void test_nested_alloc() {
+  struct Obj *o = (struct Obj *)malloc(sizeof(struct Obj));
+  use(o);   // no-warning
+  free(o);
+  use(o);   // expected-warning{{Use of memory after it is freed}}
+}
+
+void test_nested_field() {
+    struct Obj *o = (struct Obj *)malloc(sizeof(struct Obj));
+    int *f = &o->field;
+    free(o);
+    use(f); // expected-warning{{Use of memory after it is freed}}
----------------
steakhal wrote:

```suggestion
    use(f); // expected-warning{{Use of memory after it is released}}
```

https://github.com/llvm/llvm-project/pull/152462