From 08b3b2ab633b16b117603a0ebb286c42ef266880 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <hyd_danmar@users.sourceforge.net>
Date: Wed, 20 Feb 2008 18:20:59 +0000
Subject: [PATCH] CheckUnsignedDivision: Added check. Not very accurate yet.

---
 CheckOther.cpp | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 CheckOther.h   |  3 +++
 main.cpp       |  6 ++++++
 tests.cpp      | 21 ++++++++++++++++++++-
 tokenize.cpp   | 14 ++++++++++----
 5 files changed, 88 insertions(+), 5 deletions(-)

diff --git a/CheckOther.cpp b/CheckOther.cpp
index dbcb8ac1f..e7bba8825 100644
--- a/CheckOther.cpp
+++ b/CheckOther.cpp
@@ -519,5 +519,54 @@ void CheckCaseWithoutBreak()
     }
 
 }
+//---------------------------------------------------------------------------
+
+
+
+//---------------------------------------------------------------------------
+// Check for case without break
+//---------------------------------------------------------------------------
+
+void CheckUnsignedDivision()
+{
+    const char *pattern_declvar[] = { "unsigned", "int", "", NULL };
+    TOKEN *declvar = findtoken(tokens, pattern_declvar);
+    while (  declvar )
+    {
+        const char *varname = getstr( declvar, 2 );
+        if ( ! IsName(varname) )
+        {
+            declvar = findtoken( declvar->next, pattern_declvar );
+            continue;
+        }
+
+        const char *pattern_div1[] = { "/", "", NULL };
+        pattern_div1[1] = varname;
+        TOKEN *tokdiv = findtoken(declvar, pattern_div1);
+        while ( tokdiv )
+        {
+            std::ostringstream ostr;
+            ostr << FileLine(tokdiv) << ": If the result is negative it will be wrong because an operand is unsigned.";
+            ReportErr(ostr.str());
+            tokdiv = findtoken(tokdiv->next, pattern_div1);
+        }
+
+        const char *pattern_div2[] = { "", "", "/", NULL };
+        pattern_div2[1] = varname;
+        tokdiv = findtoken(declvar, pattern_div2);
+        while ( tokdiv )
+        {
+            if ( tokdiv->str[0] != ')' )    // The ')' may indicate a cast
+            {
+                std::ostringstream ostr;
+                ostr << FileLine(tokdiv) << ": If the result is negative it will be wrong because an operand is unsigned.";
+                ReportErr(ostr.str());
+            }
+            tokdiv = findtoken(tokdiv->next, pattern_div2);
+        }
+
+        declvar = findtoken(declvar->next, pattern_declvar);
+    }
+}
 
 
diff --git a/CheckOther.h b/CheckOther.h
index bdecec962..5beb5a4cb 100644
--- a/CheckOther.h
+++ b/CheckOther.h
@@ -34,6 +34,9 @@ void WarningStrTok();
 // Check for a 'case' without a 'break'
 void CheckCaseWithoutBreak();
 
+// Check for unsigned division that might create bad results
+void CheckUnsignedDivision();
+
 //---------------------------------------------------------------------------
 #endif
 
diff --git a/main.cpp b/main.cpp
index e16ed5580..4b2ff5f44 100644
--- a/main.cpp
+++ b/main.cpp
@@ -114,6 +114,12 @@ static void CppCheck(const char FileName[])
     CheckMemset();
 
 
+    // Check for unwanted unsigned division
+    // Not accurate yet. Very important to run it before 'SimplifyTokenList'
+    if ( ShowAll )
+        CheckUnsignedDivision();
+
+
     // Including header which is not needed
     if ( CheckCodingStyle )
         WarningIncludeHeader();
diff --git a/tests.cpp b/tests.cpp
index a270af360..e616da9df 100644
--- a/tests.cpp
+++ b/tests.cpp
@@ -10,6 +10,7 @@
 #include "CheckBufferOverrun.h"
 #include "CheckClass.h"
 #include "CheckMemoryLeak.h"
+#include "CheckOther.h"
 
 #include <iostream>
 #include <sstream>
@@ -27,6 +28,7 @@ static void constructors();
 static void operator_eq();
 static void memleak_in_function();
 static void memleak_in_class();
+static void division();
 //---------------------------------------------------------------------------
 
 int main()
@@ -52,6 +54,9 @@ int main()
     // Test that memory leaks in a class are detected
     memleak_in_class();
 
+    // Check for dangerous division.. such as "svar / uvar". Treating "svar" as unsigned data is not good
+    division();
+
     std::cout << "Success Rate: " 
               << SuccessCount 
               << " / " 
@@ -71,7 +76,8 @@ static void check(void (chk)(),
     tokens = tokens_back = NULL;
     std::istringstream istr(code);
     TokenizeCode( istr );
-    SimplifyTokenList();
+    if ( chk != CheckUnsignedDivision )
+        SimplifyTokenList();
 
     // Check for buffer overruns..
     errout.str("");
@@ -671,3 +677,16 @@ static void memleak_in_class()
 }
 //---------------------------------------------------------------------------
 
+static void division()
+{
+
+    const char test1[] = "void f()\n"
+                         "{\n"
+                         "    unsigned int uvar = 2;\n"
+                         "    return -2 / uvar;\n"
+                         "}\n";
+    check( CheckUnsignedDivision, __LINE__, test1, "[test.cpp:4]: If the result is negative it will be wrong because an operand is unsigned.\n" );
+
+
+}
+//---------------------------------------------------------------------------
diff --git a/tokenize.cpp b/tokenize.cpp
index afa7dd260..f9414dcdf 100644
--- a/tokenize.cpp
+++ b/tokenize.cpp
@@ -109,10 +109,6 @@ static void addtoken(const char str[], const unsigned int lineno, const unsigned
     if (str[0] == 0)
         return;
 
-    // The keyword 'unsigned' can be skipped for now.
-    if (strcmp(str,"unsigned")==0)
-        return;
-
     // Replace hexadecimal value with decimal
     char str2[50];
     memset(str2, 0, sizeof(str2));
@@ -539,6 +535,16 @@ void TokenizeCode(std::istream &code, const unsigned int FileIndex)
 
 void SimplifyTokenList()
 {
+
+    // Remove the keyword 'unsigned'
+    for ( TOKEN *tok = tokens; tok; tok = tok->next )
+    {
+        if (tok->next && strcmp(tok->next->str,"unsigned")==0)
+        {
+            DeleteNextToken( tok );
+        }
+    }
+
     // Replace constants..
     for (TOKEN *tok = tokens; tok; tok = tok->next)
     {