From 1bfe98447a85ccb78d592b39503add5e4f807520 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sat, 15 Dec 2018 11:54:00 +0100
Subject: [PATCH] FwdAnalysis: Tweak possiblyAliased

---
 lib/astutils.cpp       | 20 +++++++++++++-------
 test/testunusedvar.cpp | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index 69f685b35..0454792bb 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -1296,14 +1296,20 @@ bool FwdAnalysis::possiblyAliased(const Token *expr, const Token *startToken) co
     const bool followVar = false;
     for (const Token *tok = startToken; tok; tok = tok->previous()) {
         if (tok->str() == "{" && tok->scope()->type == Scope::eFunction)
+            break;
+
+        const Token *addrOf = nullptr;
+        if (Token::Match(tok, "& %name% ="))
+            addrOf = tok->tokAt(2)->astOperand2();
+        else if (tok->isUnaryOp("&"))
+            addrOf = tok->astOperand1();
+        else if (Token::simpleMatch(tok, "std :: ref ("))
+            addrOf = tok->tokAt(3)->astOperand2();
+        else
             continue;
-        if (isSameExpression(mCpp, macro, expr, tok, mLibrary, pure, followVar)) {
-            const Token *parent = tok->astParent();
-            if (parent && parent->isUnaryOp("&"))
-                return true;
-            if (parent && Token::Match(parent->tokAt(-2), "& %name% ="))
-                return true;
-            if (parent && Token::simpleMatch(parent->tokAt(-3), "std :: ref ("))
+
+        for (const Token *subexpr = expr; subexpr; subexpr = subexpr->astOperand1()) {
+            if (isSameExpression(mCpp, macro, subexpr, addrOf, mLibrary, pure, followVar))
                 return true;
         }
     }
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index eb42ce20e..691843dfb 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -150,6 +150,7 @@ private:
         TEST_CASE(localvarStruct3);
         TEST_CASE(localvarStruct5);
         TEST_CASE(localvarStruct6);
+        TEST_CASE(localvarStruct7);
         TEST_CASE(localvarStructArray);
 
         TEST_CASE(localvarOp);          // Usage with arithmetic operators
@@ -3279,6 +3280,46 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvarStruct7() {
+        functionVariableUsage("struct IMAPARG {\n"
+                              "  void *text;\n"
+                              "};\n"
+                              "\n"
+                              "void fun() {\n"
+                              "  IMAPARG *args, aatt;\n"
+                              "  args = &aatt;\n"
+                              "  aatt.text = tmp;\n"
+                              "  dostuff(args);\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+
+        functionVariableUsage("struct ARG {\n"
+                              "  void *a;\n"
+                              "  void *b;\n"
+                              "};\n"
+                              "\n"
+                              "void fun() {\n"
+                              "  ARG aatt;\n"
+                              "  int *p = &aatt.b;\n"
+                              "  aatt.a = 123;\n"
+                              "  dostuff(p);\n"
+                              "}");
+        ASSERT_EQUALS("[test.cpp:9]: (style) Variable 'aatt.a' is assigned a value that is never used.\n", errout.str());
+
+        functionVariableUsage("struct AB {\n"
+                              "  int a;\n"
+                              "  int b;\n"
+                              "};\n"
+                              "\n"
+                              "void fun() {\n"
+                              "  AB ab;\n"
+                              "  int &a = ab.a;\n"
+                              "  ab.a = 123;\n"
+                              "  dostuff(a);\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarStructArray() {
         // #3633 - detect that struct array is assigned a value
         functionVariableUsage("void f() {\n"