gdb is not a compiler, it will not do the (not-so-)nice user-defined type conversions for you. If you wish to call a function that wants a string, you need to give it a string, not a const char*.
Unfortunately, gdb cannot construct an std::string for you on the command line, again because it is not a compiler and object creation is not a simple function call.
So you will have to add a little helper function to your program, that would take a const char* and return an std::string&. Note the reference here. It cannot return by value, because then gdb will not be able to pass the result by const reference (it’s not a compiler!) You can choose to return a reference to a static object, or to an object allocated on the heap. In the latter case it will leak memory, but this is not a big deal since the function is meant to be called only from the debugger anyway.
std::string& SSS (const char* s)
{
return *(new std::string(s));
}
Then in gdb
gdb> p (paramNode_.px)->Get(SSS("domain"))
should work.