Fixed #7718 (False positive: out of bounds of already resized std::string)

lib/checkbufferoverrun.cpp

@@ -1561,6 +1561,9 @@ void CheckBufferOverrun::bufferOverrun()
             //  char arr[10] = "123";
             //  arr[7] = 'x'; // warning: arr[7] is inside the array bounds, but past the string's end
 
+            if (tok->valueType() && tok->valueType()->type == ValueType::Type::CONTAINER)
+                continue;
+
             const ArrayInfo arrayInfo(tok->varId(), varname, 1U, Token::getStrSize(strtoken));
             valueFlowCheckArrayIndex(tok->next(), arrayInfo);
         } else {

test/testbufferoverrun.cpp

@@ -74,6 +74,8 @@ private:
     }
 
     void run() override {
+        LOAD_LIB_2(settings0.library, "std.cfg");
+
         settings0.addEnabled("warning");
         settings0.addEnabled("style");
         settings0.addEnabled("portability");
@@ -3124,6 +3126,14 @@ private:
               "    s[10] = 0;\n"
               "}");
         ASSERT_EQUALS("", errout.str());
+
+        check("void foo()\n" // #7718
+              "{\n"
+              "    std::string s = \"123\";\n"
+              "    s.resize(100);\n"
+              "    s[10] = 0;\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
     }
 
     // data is allocated with alloca