Instead of having a solution specific to the printf command, Pedro
suggested adding a general purpose function $_as_string() that would
cover this use case and more.
So, in order to print the textual label of an enum, one can use:
(gdb) printf "Visiting node of type %s\n", $_as_string(node)
Visiting node of type NODE_INTEGER
gdb/ChangeLog:
* data-directory/Makefile.in (PYTHON_FILE_LIST): Install
gdb/function/as_string.py.
* python/lib/gdb/function/as_string.py: New file.
* NEWS: Mention the new $_as_string function.
gdb/testsuite/ChangeLog:
* gdb.python/py-as-string.exp: New file.
* gdb.python/py-as-string.c: New file.