From bd83630f2e322c4abb2ee58897fae348d0c7e5e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Fri, 20 Dec 2019 18:31:44 +0100
Subject: [PATCH] Fixed #8990 (False positive: struct member not used (union))

---
 lib/checkunusedvar.cpp |  4 ++++
 test/testunusedvar.cpp | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 42b507daf..9f4ea36d8 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1221,6 +1221,10 @@ void CheckUnusedVar::checkFunctionVariableUsage()
 
             const Token *expr = varDecl ? varDecl : tok->astOperand1();
 
+            // Is variable in lhs a union member?
+            if (tok->previous() && tok->previous()->variable() && tok->previous()->variable()->nameToken()->scope()->type == Scope::eUnion)
+                continue;
+
             FwdAnalysis fwdAnalysis(mTokenizer->isCPP(), mSettings->library);
             if (fwdAnalysis.unusedValue(expr, start, scope->bodyEnd)) {
                 if (!bailoutTypeName.empty() && bailoutTypeName != "auto") {
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 2a0ba8ffe..dbeba8bcd 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -161,6 +161,7 @@ private:
         TEST_CASE(localvarStruct5);
         TEST_CASE(localvarStruct6);
         TEST_CASE(localvarStruct7);
+        TEST_CASE(localvarStruct8);
         TEST_CASE(localvarStructArray);
 
         TEST_CASE(localvarOp);          // Usage with arithmetic operators
@@ -3445,6 +3446,25 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvarStruct8() {
+        functionVariableUsage("struct s {\n"
+                              "     union {\n"
+                              "         struct {\n"
+                              "             int fld1 : 16;\n"
+                              "             int fld2 : 16;\n"
+                              "         };\n"
+                              "         int raw;\n"
+                              "     };\n"
+                              "};\n"
+                              "\n"
+                              "void foo() {\n"
+                              "      struct s test;\n"
+                              "      test.raw = 0x100;\n"
+                              "      dostuff(test.fld1, test.fld2);\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarStructArray() {
         // #3633 - detect that struct array is assigned a value
         functionVariableUsage("void f() {\n"