[clang] [analyzer] Fix StackAddrEscapeChecker crash on temporary object fields (PR #66493)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang
            
<details>
<summary>Changes</summary>
Basically, the issue was that we should have unwrap the base region before we special handle temp object regions.

Fixes https://github.com/llvm/llvm-project/issues/66221

I also decided to add some extra range information to the diagnostics to make it consistent with the other reporting path.
--
Full diff: https://github.com/llvm/llvm-project/pull/66493.diff

2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp (+4-2) 
- (added) clang/test/Analysis/stackaddrleak.cpp (+24) 


<pre>
diff --git a/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
index 19ff8c8e2a171ae..23a774931b21dec 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StackAddrEscapeChecker.cpp
@@ -369,7 +369,7 @@ void StackAddrEscapeChecker::checkEndFunction(const ReturnStmt *RS,
                                   &quot;Stack address stored into global variable&quot;);
 
   for (const auto &amp;P : Cb.V) {
-    const MemRegion *Referrer = P.first;
+    const MemRegion *Referrer = P.first-&gt;getBaseRegion();
     const MemRegion *Referred = P.second;
 
     // Generate a report for this bug.
@@ -384,6 +384,8 @@ void StackAddrEscapeChecker::checkEndFunction(const ReturnStmt *RS,
           &lt;&lt; CommonSuffix;
       auto Report =
           std::make_unique&lt;PathSensitiveBugReport&gt;(*BT_stackleak, Out.str(), N);
+      if (Range.isValid())
+        Report-&gt;addRange(Range);
       Ctx.emitReport(std::move(Report));
       return;
     }
@@ -398,7 +400,7 @@ void StackAddrEscapeChecker::checkEndFunction(const ReturnStmt *RS,
     }(Referrer-&gt;getMemorySpace());
 
     // This cast supposed to succeed.
-    const VarRegion *ReferrerVar = cast&lt;VarRegion&gt;(Referrer-&gt;getBaseRegion());
+    const auto *ReferrerVar = cast&lt;VarRegion&gt;(Referrer);
     const std::string ReferrerVarName =
         ReferrerVar-&gt;getDecl()-&gt;getDeclName().getAsString();
 
diff --git a/clang/test/Analysis/stackaddrleak.cpp b/clang/test/Analysis/stackaddrleak.cpp
new file mode 100644
index 000000000000000..5828f2ac6e78c8d
--- /dev/null
+++ b/clang/test/Analysis/stackaddrleak.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
+
+void *operator new(unsigned long, void *p) { return p; }
+
+struct myfunction {
+  union storage_t {
+    char buffer[100];
+    unsigned long long max_align;
+  } storage;
+
+  template &lt;typename Func&gt; myfunction(Func fn) {
+    new (&amp;storage.buffer) Func(fn);
+  }
+  void operator()();
+};
+
+myfunction create_func() {
+  int n;
+  auto c = [&amp;n] {};
+  return c; // expected-warning {{Address of stack memory associated with local variable &#x27;n&#x27; is still referred to by a temporary object on the stack upon returning to the caller.  This will be a dangling reference}}
+}
+void gh_66221() {
+  create_func()();
+}
</pre>
</details>


https://github.com/llvm/llvm-project/pull/66493