From d1ae844dc2cc58bc762135d9500464c61d50f4f9 Mon Sep 17 00:00:00 2001
From: Rashmi Mudduluru <r_mudduluru@apple.com>
Date: Thu, 15 Jun 2023 16:45:28 -0700
Subject: [PATCH] [-Wunsafe-buffer-usage] Do not emit fixits for C++ interfaces
 with C linkage

Differential Revision: https://reviews.llvm.org/D153064
---
 clang/lib/Analysis/UnsafeBufferUsage.cpp           | 12 +++++++++++
 .../SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp | 24 ++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 clang/test/SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp

diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 999b94a..49229a6 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -2139,6 +2139,18 @@ void clang::checkUnsafeBufferUsage(const Decl *D,
                                    UnsafeBufferUsageHandler &Handler,
                                    bool EmitSuggestions) {
   assert(D && D->getBody());
+  
+  // Do not emit fixit suggestions for functions declared in an
+  // extern "C" block.
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+      for (FunctionDecl *FReDecl : FD->redecls()) {
+      if (FReDecl->isExternC()) {
+        EmitSuggestions = false;
+        break;
+      }
+    }
+  }
+  
   WarningGadgetSets UnsafeOps;
   FixableGadgetSets FixablesForAllVars;
 
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-c-linkage.cpp
new file mode 100644
index 0000000..6c13409
--- /dev/null
+++ b/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);
+}
-- 
2.7.4