[clang] [Clang][Sema] Add fortify warnings for fread, fwrite, and fgets (PR #204337)

[Radovan Božić via cfe-commits]

================
@@ -1496,7 +1522,24 @@ void Sema::checkFortifiedBuiltinMemoryFunction(FunctionDecl *FD,
     Checker.checkSourceOverread(/*SrcArgIdx=*/0, /*SizeArgIdx=*/2);
     break;
   }
-
+  case Builtin::BIfread: {
+    DiagID = diag::warn_fortify_source_overflow;
+    SourceSize = Checker.ComputeExplicitObjectSizeArgumentProduct(1, 2);
+    DestinationSize = Checker.ComputeSizeArgument(0);
+    break;
+  }
+  case Builtin::BIfwrite: {
+    DiagID = diag::warn_fortify_source_overread;
----------------
bozicrHT wrote:

I don't think so. I kept a fortify-specific diagnostic because `warn_stringop_overread` belongs to `-Wstringop-overread`, while this check is controlled by `-Wforitfy-source`.

https://github.com/llvm/llvm-project/pull/204337