While debugging, you can use the Debug Console to print memory, including the content of strings that are clipped by default in the variables and watch windows.
View > Open View > Debug Console
From there, send gdb a command to print memory – 300 characters of a string in this example:
-exec x/300sb Query.c_str()
Make sure you use a char*, not a string object – if it’s a string, just tack on .c_str().