From da15efb3f6960aedc25a664412dfcd91555963e5 Mon Sep 17 00:00:00 2001
From: Dmitry-Me <wipedout@yandex.ru>
Date: Thu, 24 Sep 2015 18:29:08 +0200
Subject: [PATCH] Fix FN for distinct structs with identical members

---
 lib/checkunusedvar.cpp | 31 ++++++++++++++++++++-----------
 test/testunusedvar.cpp | 28 ++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index f42eb167a..76371f860 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1232,34 +1232,43 @@ void CheckUnusedVar::checkStructMemberUsage()
             structname.clear();
 
         if (!structname.empty() && Token::Match(tok, "[{;]")) {
-            // declaring a POD variable?
+            // declaring a POD member variable?
             if (!tok->next()->isStandardType())
                 continue;
 
-            // Declaring struct variable..
-            const std::string* varname;
+            // Declaring struct member variable..
+            const std::string* memberVarName;
 
             if (Token::Match(tok->next(), "%type% %name% [;[]"))
-                varname = &tok->strAt(2);
+                memberVarName = &tok->strAt(2);
             else if (Token::Match(tok->next(), "%type% %type%|* %name% [;[]"))
-                varname = &tok->strAt(3);
+                memberVarName = &tok->strAt(3);
             else if (Token::Match(tok->next(), "%type% %type% * %name% [;[]"))
-                varname = &tok->strAt(4);
+                memberVarName = &tok->strAt(4);
             else
                 continue;
 
-            // Check if the struct variable is used anywhere in the file
-            const std::string usagePattern(". " + *varname);
+            // Check if the struct member variable is used anywhere in the file
+            const std::string usagePattern(". " + *memberVarName);
             bool used = false;
-            for (const Token *tok2 = _tokenizer->tokens(); tok2; tok2 = tok2->next()) {
-                if (Token::simpleMatch(tok2, usagePattern.c_str())) {
+            const Token* usageTok = _tokenizer->tokens();
+            while ((usageTok = Token::findsimplematch(usageTok->next(), usagePattern.c_str())) != nullptr) {
+                // Locate the containing struct variable and ensure it's of the same type, not a random struct
+                const Token* structVarTok = usageTok->previous();
+                // Walk backwards over array accesses
+                while (structVarTok && structVarTok->link())
+                    structVarTok = structVarTok->link()->previous();
+                if (!structVarTok)
+                    continue;
+                const Variable* structVar = structVarTok->variable();
+                if (structVar && structVar->type() && structVar->type()->name() == structname) {
                     used = true;
                     break;
                 }
             }
 
             if (!used) {
-                unusedStructMemberError(tok->next(), structname, *varname, tok->scope()->type == Scope::eUnion);
+                unusedStructMemberError(tok->next(), structname, *memberVarName, tok->scope()->type == Scope::eUnion);
             }
         }
     }
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index 96d1fcb54..b6c5fefc0 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -222,6 +222,34 @@ private:
                       "[test.cpp:4]: (style) union member 'abc::b' is never used.\n"
                       "[test.cpp:5]: (style) union member 'abc::c' is never used.\n", errout.str());
 
+        checkStructMemberUsage("struct A\n"
+                               "{\n"
+                               "    int a;\n"
+                               "};\n"
+                               "struct B\n"
+                               "{\n"
+                               "    int a;\n"
+                               "};\n"
+                               "void foo()\n"
+                               "{\n"
+                               "    A a;\n"
+                               "    a.a;\n"
+                               "}");
+        ASSERT_EQUALS("[test.cpp:7]: (style) struct member 'B::a' is never used.\n", errout.str());
+
+        checkStructMemberUsage("struct A\n"
+                               "{\n"
+                               "    int a;\n"
+                               "};\n"
+                               "struct B\n"
+                               "{\n"
+                               "    int a;\n"
+                               "};\n"
+                               "void foo(A* a)\n"
+                               "{\n"
+                               "    a->a;\n"
+                               "}");
+        ASSERT_EQUALS("[test.cpp:7]: (style) struct member 'B::a' is never used.\n", errout.str());
     }
 
     void structmember2() {