[clang] [clang] Implement -Walloc-size diagnostic option (PR #150028)

[Vladimir Vuksanovic via cfe-commits]

================
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Walloc-size %s
+struct Foo { int x[10]; };
+
+typedef __typeof__(sizeof(int)) size_t;
+void *my_malloc(size_t) __attribute__((alloc_size(1)));
+void *my_calloc(size_t, size_t) __attribute__((alloc_size(2, 1)));
+
+void foo_consumer(struct Foo* p);
+
+void alloc_foo(void) {
+  struct Foo *ptr1 = my_malloc(sizeof(struct Foo));
+  struct Foo *ptr2 = my_malloc(sizeof(*ptr2));
+  struct Foo *ptr3 = my_calloc(1, sizeof(*ptr3));
+  struct Foo *ptr4 = my_calloc(sizeof(*ptr4), 1);
+  struct Foo (*ptr5)[5] = my_malloc(sizeof(*ptr5));
+  void *ptr6 = my_malloc(4);
+
+  // Test insufficient size with different allocation functions.
+  struct Foo *ptr7 = my_malloc(sizeof(ptr7));      // expected-warning {{allocation of insufficient size '8' for type 'struct Foo' with size '40'}}
+  struct Foo *ptr8 = my_calloc(1, sizeof(ptr8));   // expected-warning {{allocation of insufficient size '8' for type 'struct Foo' with size '40'}}
+  struct Foo *ptr9 = my_calloc(sizeof(ptr9), 1); // expected-warning {{allocation of insufficient size '8' for type 'struct Foo' with size '40'}}
+
+  // Test function arguments.
+  foo_consumer(my_malloc(4)); // expected-warning {{allocation of insufficient size '4' for type 'struct Foo' with size '40'}}
+
+  // Test explicit cast.
+  struct Foo *ptr10 = (struct Foo *)my_malloc(sizeof(*ptr10));
+  struct Foo *ptr11 = (struct Foo *)my_malloc(sizeof(ptr11));    // expected-warning {{allocation of insufficient size '8' for type 'struct Foo' with size '40'}}
+  struct Foo *ptr12 = (struct Foo *)my_calloc(1, sizeof(ptr12)); // expected-warning {{allocation of insufficient size '8' for type 'struct Foo' with size '40'}}
+  struct Foo *ptr13 = (struct Foo *)my_malloc(4);                // expected-warning {{allocation of insufficient size '4' for type 'struct Foo' with size '40'}}
+  void *ptr14 = (struct Foo *)my_malloc(4);                      // expected-warning {{allocation of insufficient size '4' for type 'struct Foo' with size '40'}}
+
+  struct Foo *ptr15 = (void *)(struct Foo *)my_malloc(4); // expected-warning 2 {{allocation of insufficient size '4' for type 'struct Foo' with size '40'}}
+  int *ptr16 = (unsigned *)(void *)(int *)my_malloc(1);   // expected-warning {{initializing 'int *' with an expression of type 'unsigned int *' converts between pointers to integer types with different sign}}
+                                                       // expected-warning at -1 {{allocation of insufficient size '1' for type 'int' with size '4'}}
+                                                       // expected-warning at -2 {{allocation of insufficient size '1' for type 'unsigned int' with size '4'}}
+  int *ptr17 = (void *)(int *)my_malloc(1);               // expected-warning {{allocation of insufficient size '1' for type 'int' with size '4'}}
+                                                       // expected-warning at -1 {{allocation of insufficient size '1' for type 'int' with size '4'}}
+  (void)(int *)my_malloc(1);                              // expected-warning {{allocation of insufficient size '1' for type 'int' with size '4'}}
+}
----------------
vvuksanovic wrote:

That is an interesting case. It should be okay, and GCC doesn't emit a warning as well. Though the return value of `malloc(0)`  is implementation defined.

https://github.com/llvm/llvm-project/pull/150028