From c8d688607a619f7dbc10b23dc98702b5d33d11f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sun, 16 Dec 2018 19:01:05 +0100
Subject: [PATCH] Fixed #8901 (Unused value: const variable initialization)

---
 lib/astutils.cpp       |  5 ++++-
 lib/checkunusedvar.cpp | 16 +++++++++++-----
 test/testunusedvar.cpp |  5 +++++
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index bab173fc7..ecd372d7d 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -1138,9 +1138,12 @@ struct FwdAnalysis::Result FwdAnalysis::checkRecursive(const Token *expr, const
         if (exprVarIds.find(tok->varId()) != exprVarIds.end()) {
             const Token *parent = tok;
             bool other = false;
+            bool same = false;
             while (Token::Match(parent->astParent(), ".|::|[")) {
                 parent = parent->astParent();
-                if (Token::Match(parent, ". %var%") && parent->next()->varId() && exprVarIds.find(parent->next()->varId()) == exprVarIds.end()) {
+                if (parent && isSameExpression(mCpp, false, expr, parent->astOperand1(), mLibrary, false, false, nullptr))
+                    same = true;
+                if (!same && Token::Match(parent, ". %var%") && parent->next()->varId() && exprVarIds.find(parent->next()->varId()) == exprVarIds.end()) {
                     other = true;
                     break;
                 }
diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index 984a7fb42..f85b789a5 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1236,6 +1236,16 @@ void CheckUnusedVar::checkFunctionVariableUsage()
             if (Token::simpleMatch(tok, "try {"))
                 // todo: check try blocks
                 tok = tok->linkAt(1);
+            const Token *varDecl = nullptr;
+            if (tok->variable() && tok->variable()->nameToken() == tok) {
+                const Token * eq = tok->next();
+                while (Token::simpleMatch(eq, "["))
+                    eq = eq->link()->next();
+                if (Token::simpleMatch(eq, "=")) {
+                    varDecl = tok;
+                    tok = eq;
+                }
+            }
             // not assignment/initialization => continue
             if ((!tok->isAssignmentOp() || !tok->astOperand1()) && !(Token::Match(tok, "%var% (") && tok->variable() && tok->variable()->nameToken() == tok))
                 continue;
@@ -1271,11 +1281,7 @@ void CheckUnusedVar::checkFunctionVariableUsage()
             // Is there a redundant assignment?
             const Token *start = tok->findExpressionStartEndTokens().second->next();
 
-            const Token *expr = tok->astOperand1();
-            if (Token::Match(expr->previous(), "%var% [") && expr->previous()->variable() && expr->previous()->variable()->nameToken() == expr->previous())
-                expr = expr->previous();
-            else if (Token::Match(expr, "& %var% ="))
-                expr = expr->next();
+            const Token *expr = varDecl ? varDecl : tok->astOperand1();
 
             FwdAnalysis fwdAnalysis(mTokenizer->isCPP(), mSettings->library);
             if (fwdAnalysis.unusedValue(expr, start, scope->bodyEnd))
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 415e403b7..ee1df38ff 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -3966,6 +3966,11 @@ private:
                               "}");
         ASSERT_EQUALS("[test.cpp:2]: (style) Variable 's' is assigned a value that is never used.\n", errout.str());
 
+        functionVariableUsage("void foo() {\n" // #8901
+                              "    const std::string s = \"foo\";\n"
+                              "}");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Variable 's' is assigned a value that is never used.\n", errout.str());
+
         functionVariableUsage("std::string foo() {\n"
                               "    std::string s;\n" // Class instances are initialized. Assignment is not necessary
                               "    return s;\n"