Fixed #2976 (False positive: array out of bounds)

lib/checkbufferoverrun.cpp

@@ -894,6 +894,12 @@ void CheckBufferOverrun::checkScope(const Token *tok, const std::vector<std::str
             break;
         }
 
+        // reassign buffer => bailout
+        if (varid > 0 &&
+            Token::Match(tok, "[;{}] %varid% =", varid) &&
+            !Token::Match(tok->tokAt(3), "%varid%", varid))
+            break;
+
         // Array index..
         if (varid > 0)
         {

test/testbufferoverrun.cpp

@@ -2497,6 +2497,13 @@ private:
               "    s[10] = 0;\n"
               "}\n");
         ASSERT_EQUALS("[test.cpp:4]: (error) Array 's[1]' index 10 out of bounds\n", errout.str());
+
+        check("void foo() {\n"
+              "    const char *s = \"\";\n"
+              "    s = y();\n"
+              "    s[10] = 0;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 
     // data is allocated with alloca