[clang] [Sema] Suggest missing format attributes (PR #166738)

[via cfe-commits]

================
@@ -7001,6 +7005,85 @@ bool Sema::CheckFormatString(const FormatMatchesAttr *Format,
   return false;
 }
 
+static void CheckMissingFormatAttributes(Sema *S, FormatStringType FormatType,
+                                         unsigned FormatIdx, unsigned FirstArg,
+                                         ArrayRef<const Expr *> Args,
+                                         Sema::FormatArgumentPassingKind APK,
+                                         unsigned CallerParamIdx,
+                                         SourceLocation Loc) {
+  const FunctionDecl *Caller = S->getCurFunctionDecl();
+  if (!Caller)
+    return;
----------------
apple-fcloutier wrote:

This will always fail in Objective-C because ObjCMethodDecl does not inherit from FunctionDecl. Would you add an Objective-C test to ensure this works? If you're not super familiar with it, the declaration/use syntax should be:

```
#include <stdarg.h>

@interface Foo
-(void)myprintf:(const char *)fmt, ... __attribute__((format(printf, 1, 2)));
-(void)myvprintf:(const char *)fmt list:(va_list)ap __attribute__((format(printf, 1, 0)));
@end

void bar(Foo *f) {
    [f myprintf:"hello %i", 123];
}

void baz(Foo *f, const char *fmt, va_list ap) {
    [f myvprintf:fmt list:ap];
}
```

Happy to answer other questions you may have.

https://github.com/llvm/llvm-project/pull/166738