From 6de91d6386303757ffee9c39addfb56b7cf7c6b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Fri, 2 Oct 2020 20:22:09 +0200
Subject: [PATCH] Fixed #9707 (False positive: unreadVariable, union)

---
 lib/checkunusedvar.cpp |  4 ++++
 lib/symboldatabase.cpp | 20 ++++++++++++++++++++
 lib/symboldatabase.h   | 15 ++++-----------
 test/testunusedvar.cpp | 13 +++++++++++++
 4 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 33ed4f12b..7e443fef4 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1231,6 +1231,10 @@ void CheckUnusedVar::checkFunctionVariableUsage()
                 if (op1Var->nameToken()->isAttributeUnused())
                     continue;
 
+                // Avoid FP for union..
+                if (op1Var->type() && op1Var->type()->isUnionType())
+                    continue;
+
                 // Bailout for unknown template classes, we have no idea what side effects such assignments have
                 if (mTokenizer->isCPP() &&
                     op1Var->isClass() &&
diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 5a01d6fc3..2ce32c29f 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -2818,6 +2818,26 @@ void SymbolDatabase::addNewFunction(Scope **scope, const Token **tok)
     }
 }
 
+bool Type::isClassType() const
+{
+    return classScope && classScope->type == Scope::ScopeType::eClass;
+}
+
+bool Type::isEnumType() const
+{
+    return classScope && classScope->type == Scope::ScopeType::eEnum;
+}
+
+bool Type::isStructType() const
+{
+    return classScope && classScope->type == Scope::ScopeType::eStruct;
+}
+
+bool Type::isUnionType() const
+{
+    return classScope && classScope->type == Scope::ScopeType::eUnion;
+}
+
 const Token *Type::initBaseInfo(const Token *tok, const Token *tok1)
 {
     // goto initial '{'
diff --git a/lib/symboldatabase.h b/lib/symboldatabase.h
index d54164681..18064b735 100644
--- a/lib/symboldatabase.h
+++ b/lib/symboldatabase.h
@@ -131,22 +131,15 @@ public:
         return classDef ? classDef->str() : emptyString;
     }
 
-    bool isClassType() const {
-        return classDef && classDef->str() == "class";
-    }
-
-    bool isEnumType() const {
-        return classDef && classDef->str() == "enum";
-    }
+    bool isClassType() const;
+    bool isEnumType() const;
+    bool isStructType() const;
+    bool isUnionType() const;
 
     bool isTypeAlias() const {
         return classDef && classDef->str() == "using";
     }
 
-    bool isStructType() const {
-        return classDef && classDef->str() == "struct";
-    }
-
     const Token *initBaseInfo(const Token *tok, const Token *tok1);
 
     const Function* getFunction(const std::string& funcName) const;
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 37e7c7bdf..19ec9cf5a 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -171,6 +171,7 @@ private:
         TEST_CASE(localvarStruct8);
         TEST_CASE(localvarStruct9);
         TEST_CASE(localvarStructArray);
+        TEST_CASE(localvarUnion1);
 
         TEST_CASE(localvarOp);          // Usage with arithmetic operators
         TEST_CASE(localvarInvert);      // Usage with inverted variable
@@ -3625,6 +3626,18 @@ private:
         ASSERT_EQUALS("[test.cpp:3]: (style) Variable 'x[0].a' is assigned a value that is never used.\n", errout.str());
     }
 
+    void localvarUnion1() {
+        // #9707
+        functionVariableUsage("static short read(FILE *fp) {\n"
+                              "    typedef union { short s; unsigned char c[2]; } u;\n"
+                              "    u x;\n"
+                              "    x.c[0] = fgetuc(fp);\n"
+                              "    x.c[1] = fgetuc(fp);\n"
+                              "    return x.s;\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarOp() {
         const char op[] = "+-*/%&|^";
         for (const char *p = op; *p; ++p) {