[clang] [Clang] Add diagnostic about "%P" specifier with Objective-C pointers (#89968) (PR #89977)

[Jared Grubb via cfe-commits]

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@@ -44,15 +44,18 @@ void test_os_log_format(const char *pc, int i, void *p, void *buf) {
 }
 
 // Test os_log_format primitive with ObjC string literal format argument.
-void test_objc(const char *pc, int i, void *p, void *buf, NSString *nss) {
+void test_objc(const char *pc, int i, void *p, void *buf, NSString *nss, id obj) {
   __builtin_os_log_format(buf, @"");
   __builtin_os_log_format(buf, @"%d"); // expected-warning {{more '%' conversions than data arguments}}
   __builtin_os_log_format(buf, @"%d", i);
+
   __builtin_os_log_format(buf, @"%P", p); // expected-warning {{using '%P' format specifier without precision}}
   __builtin_os_log_format(buf, @"%.10P", p);
   __builtin_os_log_format(buf, @"%.*P", p); // expected-warning {{field precision should have type 'int', but argument has type 'void *'}}
   __builtin_os_log_format(buf, @"%.*P", i, p);
   __builtin_os_log_format(buf, @"%.*P", i, i); // expected-warning {{format specifies type 'void *' but the argument has type 'int'}}
+  __builtin_os_log_format(buf, @"%.8P", nss);    // expected-warning {{using '%P' format specifier with an Objective-C pointer results in dumping runtime object structure, not object value}}
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jaredgrubb wrote:

I don't think so, but I can be convinced. IMO, using a `(void*)` cast could be the escape-hatch if someone actually really _does_ want to dump the ObjC runtime structure but also squash this warning.

https://github.com/llvm/llvm-project/pull/89977