From 1f01845efbd12e45f7095fe4af8b70d2ca2dd0df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sun, 24 Oct 2021 21:22:06 +0200
Subject: [PATCH] Fixed #10531 (FP unreadVariable with reference and *=)

---
 lib/astutils.cpp       |  2 ++
 test/testunusedvar.cpp | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index a2a15ce25..83161c87f 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -2977,6 +2977,8 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
             } else if (Token::Match(parent->astParent(), "%assign%") && !parent->astParent()->astParent() && parent == parent->astParent()->astOperand1()) {
                 if (mWhat == What::Reassign)
                     return Result(Result::Type::BAILOUT, parent->astParent());
+                if (mWhat == What::UnusedValue && (!parent->valueType() || parent->valueType()->reference != Reference::None))
+                    return Result(Result::Type::BAILOUT, parent->astParent());
                 continue;
             } else if (mWhat == What::UnusedValue && parent->isUnaryOp("&") && Token::Match(parent->astParent(), "[,(]")) {
                 // Pass variable to function the writes it
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 4247af5cb..03479a7ef 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -119,6 +119,7 @@ private:
         TEST_CASE(localvar57); // #8974 - increment
         TEST_CASE(localvar58); // #9901 - increment false positive
         TEST_CASE(localvar59); // #9737
+        TEST_CASE(localvar60);
         TEST_CASE(localvarloops); // loops
         TEST_CASE(localvaralias1);
         TEST_CASE(localvaralias2); // ticket #1637
@@ -3191,6 +3192,16 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvar60() { // #10531
+        functionVariableUsage("void Scale(double scale) {\n"
+                              "    for (int i = 0; i < m_points.size(); ++i) {\n"
+                              "        auto& p = m_points[i];\n"
+                              "        p += scale;\n"
+                              "    }\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarloops() {
         // loops
         functionVariableUsage("void fun(int c) {\n"