calling operator<< in gdb

For me call operator<< ran without error, but didn't print. Turns out I needed a call to flush. Here's a useful function you can put in .gdbinit:

define str
    call (void)operator<<(std::cout, $arg0)
    call (void)std::cout.flush()
    printf "\n"
end

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.

You can also define a function like:

define printType
call operator<<(std::ostream&, const $arg0 &)(std::cerr, $arg1)
end

And use it like:

printType ClassX objectOfClassX