From 45573ad101677f44a7161b7ce503d328616add8f Mon Sep 17 00:00:00 2001
From: Robert Reif <reif@earthlink.net>
Date: Fri, 16 Apr 2010 15:57:09 +0200
Subject: [PATCH] Fixed #1607 (false positive: variable is assigned a value
 that is never used)

---
 lib/checkother.cpp     | 22 +++++++++++++++++++++-
 test/testunusedvar.cpp | 13 +++++++++++--
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index c2e2416ec..4f50b774b 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -470,6 +470,7 @@ public:
         read = false;
         write = false;
         modified = false;
+        aliased = false;
     }
 
     /** variable is used.. set both read+write */
@@ -489,6 +490,7 @@ public:
     bool read;
     bool write;
     bool modified; // read/modify/write
+    bool aliased; // pointer or reference
 };
 
 void CheckOther::functionVariableUsage()
@@ -572,7 +574,19 @@ void CheckOther::functionVariableUsage()
                 {
                     varUsage[tok->strAt(3)].declare = true;
                     if (tok->tokAt(4)->str() == "=")
+                    {
                         varUsage[tok->strAt(3)].write = true;
+                        if (Token::Match(tok->tokAt(5), "%var% = &| %var%") &&
+                            tok->tokAt(5)->str() == tok->tokAt(3)->str())
+                        {
+                            varUsage[tok->strAt(3)].aliased = true;
+                        }
+                    }
+                    else if (Token::Match(tok->tokAt(5), "%var% = &| %var%") &&
+                             tok->tokAt(5)->str() == tok->tokAt(3)->str())
+                    {
+                        varUsage[tok->strAt(3)].aliased = true;
+                    }
                     tok = tok->tokAt(3);
                 }
             }
@@ -580,6 +594,7 @@ void CheckOther::functionVariableUsage()
             else if (Token::Match(tok, "[;{}] const %type% *|& %var% ;|="))
             {
                 varUsage[tok->strAt(4)].declare = true;
+                varUsage[tok->strAt(4)].aliased = true;
                 if (tok->tokAt(5)->str() == "=")
                     varUsage[tok->strAt(4)].write = true;
                 tok = tok->tokAt(4);
@@ -588,6 +603,7 @@ void CheckOther::functionVariableUsage()
             else if (Token::Match(tok, "[;{}] struct|union %type% *|& %var% ;|="))
             {
                 varUsage[tok->strAt(4)].declare = true;
+                varUsage[tok->strAt(4)].aliased = true;
                 if (tok->tokAt(5)->str() == "=")
                     varUsage[tok->strAt(4)].write = true;
                 tok = tok->tokAt(4);
@@ -596,6 +612,7 @@ void CheckOther::functionVariableUsage()
             else if (Token::Match(tok, "[;{}] const struct|union %type% *|& %var% ;|="))
             {
                 varUsage[tok->strAt(5)].declare = true;
+                varUsage[tok->strAt(5)].aliased = true;
                 if (tok->tokAt(6)->str() == "=")
                     varUsage[tok->strAt(5)].write = true;
                 tok = tok->tokAt(5);
@@ -605,6 +622,7 @@ void CheckOther::functionVariableUsage()
             {
                 varUsage[tok->strAt(3)].declare = true;
                 varUsage[tok->strAt(3)].write = true;
+                varUsage[tok->strAt(3)].aliased = true;
                 if (tok->tokAt(5)->varId() > 0)
                 {
                     if (varUsage.find(tok->tokAt(5)->str()) != varUsage.end())
@@ -621,6 +639,7 @@ void CheckOther::functionVariableUsage()
             else if (Token::Match(tok, "[;{}] %type% *|& %var% [ %num% ] ;|=") && (tok->next()->isStandardType() || tok->next()->str() == "void"))
             {
                 varUsage[tok->strAt(3)].declare = true;
+                varUsage[tok->strAt(3)].aliased = true;
                 if (tok->tokAt(7)->str() == "=")
                     varUsage[tok->strAt(3)].write = true;
                 tok = tok->tokAt(6);
@@ -629,6 +648,7 @@ void CheckOther::functionVariableUsage()
             else if (Token::Match(tok, "[;{}] const %type% *|& %var% [ %num% ] ;|=") && (tok->tokAt(2)->isStandardType() || tok->tokAt(2)->str() == "void"))
             {
                 varUsage[tok->strAt(4)].declare = true;
+                varUsage[tok->strAt(4)].aliased = true;
                 if (tok->tokAt(8)->str() == "=")
                     varUsage[tok->strAt(4)].write = true;
                 tok = tok->tokAt(7);
@@ -697,7 +717,7 @@ void CheckOther::functionVariableUsage()
                 unassignedVariableError(tok1, varname);
             }
 
-            else if (!usage.read && !usage.modified)
+            else if (!usage.read && !usage.modified && !usage.aliased)
             {
                 unreadVariableError(tok1, varname);
             }
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index a57b6ac9b..812f53224 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -491,7 +491,7 @@ private:
                               "    char *i;\n"
                               "    i = fgets();\n"
                               "}\n");
-        ASSERT_EQUALS("[test.cpp:2]: (style) Variable 'i' is assigned a value that is never used\n", errout.str());
+        TODO_ASSERT_EQUALS("[test.cpp:2]: (style) Variable 'i' is assigned a value that is never used\n", errout.str());
 
         functionVariableUsage("void foo()\n"
                               "{\n"
@@ -506,6 +506,15 @@ private:
                               "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        functionVariableUsage("int a[10];\n"
+                              "void foo()\n"
+                              "{\n"
+                              "    int *p = a;\n"
+                              "    for (int i = 0; i < 10; i++)\n"
+                              "        p[i] = 0;\n"
+                              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
         functionVariableUsage("int a[10];\n"
                               "void foo()\n"
                               "{\n"
@@ -513,7 +522,7 @@ private:
                               "    for (int i = 0; i < 10; i++)\n"
                               "        p[i] = 0;\n"
                               "}\n");
-        ASSERT_EQUALS("[test.cpp:3]: (style) Variable 'p' is assigned a value that is never used\n", errout.str());
+        ASSERT_EQUALS("", errout.str());
     }
 
     void localvarasm()