[clang-tidy] Don't run use-nullptr check on objective-c code.

If we compile an objective-c file with the `-std=c23` flag, this check
will warn the NULL usage, this patch fix it.

nullptr doesn't exist in objective-c.

Author: hokein

clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.h

@@ -19,7 +19,7 @@ class UseNullptrCheck : public ClangTidyCheck {
   bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
     // FIXME this should be CPlusPlus11 but that causes test cases to
     // erroneously fail.
-    return LangOpts.CPlusPlus || LangOpts.C23;
+    return LangOpts.CPlusPlus || (LangOpts.C23 && !LangOpts.ObjC);
   }
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;

clang-tools-extra/docs/ReleaseNotes.rst

@@ -219,6 +219,10 @@ Changes in existing checks
   tolerating fix-it breaking compilation when functions is used as pointers
   to avoid matching usage of functions within the current compilation unit.
 
+- Improved :doc:`modernize-use-nullptr
+  <clang-tidy/checks/modernize/use-nullptr>` check to not run on
+  objective-c code.
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/test/clang-tidy/checkers/modernize/use-nullptr-c23.m

@@ -0,0 +1,7 @@
+// RUN: %check_clang_tidy %s modernize-use-nullptr %t -- -- -std=c23
+
+#define NULL 0
+
+void test_assignment() {
+  int *p1 = NULL;
+}