Buffer overrun: Added check to detect when size argument to memset is a char constant (#213)

src/checkbufferoverrun.cpp

@@ -71,6 +71,11 @@ void CheckBufferOverrunClass::outOfBounds(const Token *tok, const std::string &w
     reportError(tok, "error", "outOfBounds", what + " is out of bounds");
 }
 
+void CheckBufferOverrunClass::sizeArgumentAsChar(const Token *tok)
+{
+    reportError(tok, "all", "sizeArgumentAsChar", "The size argument is given as a char constant");
+}
+
 //---------------------------------------------------------------------------
 
 
@@ -163,13 +168,19 @@ void CheckBufferOverrunClass::CheckBufferOverrun_CheckScope(const Token *tok, co
         {
             if (Token::Match(tok, "memset|memcpy|memmove|memcmp|strncpy|fgets"))
             {
-                if (Token::Match(tok->next(), "( %varid% , %num% , %num% )", varid) ||
+                if (Token::Match(tok->next(), "( %varid% , %any% , %any% )", varid) ||
-                    Token::Match(tok->next(), "( %var% , %varid% , %num% )", varid))
+                    Token::Match(tok->next(), "( %var% , %varid% , %any% )", varid))
                 {
-                    const char *num  = tok->strAt(6);
+                    const Token *tokSz = tok->tokAt(6);
-                    if (std::atoi(num) > total_size)
+                    if (tokSz->str()[0] == '\'')
+                        sizeArgumentAsChar(tok);
+                    else if (tokSz->isNumber())
                     {
-                        bufferOverrun(tok);
+                        const char *num  = tok->strAt(6);
+                        if (std::atoi(num) > total_size)
+                        {
+                            bufferOverrun(tok);
+                        }
                     }
                 }
             }

src/checkbufferoverrun.h

@@ -72,6 +72,7 @@ private:
     void bufferOverrun(const Token *tok);
     void strncatUsage(const Token *tok);
     void outOfBounds(const Token *tok, const std::string &what);
+    void sizeArgumentAsChar(const Token *tok);
 
     void getErrorMessages()
     {
@@ -79,6 +80,7 @@ private:
         bufferOverrun(0);
         strncatUsage(0);
         outOfBounds(0, "index");
+        sizeArgumentAsChar(0);
     }
 };
 

test/testbufferoverrun.cpp

@@ -104,6 +104,8 @@ private:
         TEST_CASE(assign1);
 
         TEST_CASE(alloc);    // Buffer allocated with new
+
+        TEST_CASE(memset1);
     }
 
 
@@ -577,6 +579,17 @@ private:
               "}\n");
         ASSERT_EQUALS(std::string("[test.cpp:4]: (all) Array index out of bounds\n"), errout.str());
     }
+
+
+    void memset1()
+    {
+        check("void foo()\n"
+              "{\n"
+              "    char s[10];\n"
+              "    memset(s, 5, '*');\n"
+              "}\n");
+        ASSERT_EQUALS(std::string("[test.cpp:4]: (all) The size argument is given as a char constant\n"), errout.str());
+    }
 };
 
 REGISTER_TEST(TestBufferOverrun)