diff --git a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
--- a/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
@@ -501,9 +501,9 @@
 
 void FunctionCognitiveComplexityCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(
-      functionDecl(
-          allOf(isDefinition(), unless(anyOf(isDefaulted(), isDeleted(),
-                                             isImplicit(), isInstantiated()))))
+      functionDecl(allOf(isDefinition(),
+                         unless(anyOf(isDefaulted(), isDeleted(), isImplicit(),
+                                      isInstantiated(), isWeak()))))
           .bind("func"),
       this);
 }
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity.cpp
--- a/clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity.cpp
@@ -1013,3 +1013,5 @@
 
   templatedFunction<void*>();
 }
+
+static void dont_crash_on_weak() __attribute__((__weakref__("__dont_crash_on_weak")));
\ No newline at end of file
diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -4647,6 +4647,19 @@
   return Node.isDefaulted();
 }
 
+/// Matches weak function declarations.
+///
+/// Given:
+/// \code
+///   void foo() __attribute__((__weakref__("__foo")));
+///   void bar();
+/// \endcode
+/// functionDecl(isWeak())
+///   matches the weak declaration foo, but not bar.
+AST_MATCHER(FunctionDecl, isWeak) {
+  return Node.isWeak();
+}
+
 /// Matches functions that have a dynamic exception specification.
 ///
 /// Given: