warn when buffer is not zero terminated after memcpy

lib/checkbufferoverrun.cpp

@@ -178,6 +178,12 @@ void CheckBufferOverrun::cmdLineArgsError(const Token *tok)
     reportError(tok, Severity::error, "insecureCmdLineArgs", "Buffer overrun possible for long cmd-line args");
 }
 
+void CheckBufferOverrun::terminateMemcpyError(const Token *tok, const std::string &varname)
+{
+    reportError(tok, Severity::warning, "terminateMemcpy",
+                "The buffer '" + varname + "' is not zero-terminated after the call to memcpy().\n"
+                "This will cause bugs later in the code if the code assumes buffer is zero-terminated.");
+}
 
 //---------------------------------------------------------------------------
 
@@ -1228,13 +1234,18 @@ void CheckBufferOverrun::checkScope(const Token *tok, const ArrayInfo &arrayInfo
             checkFunctionCall(tok, arrayInfo);
         }
 
-        if (Token::Match(tok, "strncpy ( %varid% , %str% , %num% )", arrayInfo.varid()))
+        if (Token::Match(tok, "strncpy|memcpy ( %varid% , %str% , %num% )", arrayInfo.varid()))
         {
             unsigned int num = (unsigned int)MathLib::toLongNumber(tok->strAt(6));
             if (Token::getStrLength(tok->tokAt(4)) >= total_size && total_size == num)
             {
                 if (_settings->inconclusive)
+                {
+                    if (tok->str() == "strncpy")
                         terminateStrncpyError(tok, tok->strAt(2), true);
+                    else
+                        terminateMemcpyError(tok, tok->strAt(2));
+                }
             }
         }
 

lib/checkbufferoverrun.h

@@ -217,6 +217,7 @@ public:
     void outOfBoundsError(const Token *tok, const std::string &what);
     void sizeArgumentAsCharError(const Token *tok);
     void terminateStrncpyError(const Token *tok, const std::string &varname, bool conclusive);
+    void terminateMemcpyError(const Token *tok, const std::string &varname);
     void negativeIndexError(const Token *tok, MathLib::bigint index);
     void cmdLineArgsError(const Token *tok);
     void pointerOutOfBoundsError(const Token *tok, const std::string &object);	// UB when result of calculation is out of bounds
@@ -232,6 +233,7 @@ public:
         c.outOfBoundsError(0, "index");
         c.sizeArgumentAsCharError(0);
         c.terminateStrncpyError(0, "buffer", false);
+        c.terminateMemcpyError(0, "buffer");
         c.negativeIndexError(0, -1);
         c.cmdLineArgsError(0);
         c.pointerOutOfBoundsError(0, "array");

test/testbufferoverrun.cpp

@@ -2583,6 +2583,13 @@ private:
               "    memchr(a, b, 10);\n"
               "}\n");
         TODO_ASSERT_EQUALS("[test.cpp:4]: (error) Buffer access out-of-bounds\n", "", errout.str());
+
+        check("void f()\n"
+              "{\n"
+              "    char c[6];\n"
+              "    memcpy(c,\"hello!\",sizeof(c));\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (warning) The buffer 'c' is not zero-terminated after the call to memcpy().\n", errout.str());
     }
 
     // ticket #2121 - buffer access out of bounds when using uint32_t