Google protocol buffer always throw bad allocation exception

Question

I'm newbie in google protocol buffer. And now I have a issue as below:

I have created a simple message in testMessage.proto file:

option optimize_for = SPEED;

message TestMessage
{
    optional string foo  = 1;
    optional string bar = 2;
}

Then I generated this message to testMessage.pb.h and testMessage.pb.cc files and included these files, also added libprotobuf libs to my test project. Then I wrote a simple code to use this class:

TestMessage testMsg; 
testMsg.set_foo("1234"); // set ok
testMsg.set_bar("abcd"); // set ok 
string output; 
try {   
    std::cout << testMsg.foo() << std::endl; // output foo ok
    testMsg.PrintDebugString();  // throw bad allocation exception here
    // testMsg.SerializeToString(&output); // also throw bad allocation exception here
 } catch (std::exception ex) {  
     std::cout << ex.what() << std::endl; 
 }

This code is very simple, but I cannot understand why it cannot run correctly. I googled for my issue but there is nowhere mention about it. Everyone please help me with this issue.