Index: clang/lib/Analysis/UnsafeBufferUsage.cpp
===================================================================
--- clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -2139,6 +2139,17 @@
                                    UnsafeBufferUsageHandler &Handler,
                                    bool EmitSuggestions) {
   assert(D && D->getBody());
+  
+  // Do not emit fixit suggestions for functions declared in an
+  // extern "C" block.
+  if (D->getKind() == Decl::Function) {
+    for (FunctionDecl *FReDecl : dyn_cast<FunctionDecl>(D)->redecls()) {
+      if (FReDecl->isExternC()) {
+        EmitSuggestions = false;
+      }
+    }
+  }
+  
   WarningGadgetSets UnsafeOps;
   FixableGadgetSets FixablesForAllVars;
 
Index: clang/test/SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -std=c++20 -Wunsafe-buffer-usage -fsafe-buffer-usage-suggestions -verify %s
+
+extern "C" {
+void foo(int *ptr) {
+  ptr[5] = 10;  // expected-warning{{unsafe buffer access}}
+}
+
+void bar(int *ptr);
+
+struct c_struct {
+  char *name;
+};
+}
+
+void bar(int *ptr) {
+  ptr[5] = 10;  // expected-warning{{unsafe buffer access}}
+}
+
+void call_foo(int *p) {
+  foo(p);
+  struct c_struct str;
+  str.name[7] = 9;  // expected-warning{{unsafe buffer access}}
+  bar(p);
+}