Question

How do you call operator<<(std::ostream &os, const ClassX &x) from inside gdb ?

In other words, how do you print an object in gdb ?

call std::cout<<x or call operator<<(std::cout, x) don’t seems to work for me!

Any ideas?

Answer 1

The only way I found was this:

call 'operator<<(std::ostream&, myclass&)'(mycout, c)

Since std::cout wasn’t visible to gdb for some reason, I had to resort to creating my own like this:

std::ostream mycout(std::cout.rdbuf());

You haven’t stated any reasons for wanting to do this but won’t print yourvariable be easier?

If this is an absolute must you could have a Print method in your class and call that from operator<< and then call the Print method on your object from gdb.

Do take note that stdout is probably buffered in gdb so you won’t be seeing any output unless you redirect it somehow.

See this discussion from gdb’s mailing archive regarding this issue.