"Oliver" == Oliver Buchtala <oliver.buchtala@googlemail.com> writes:
Oliver> here the doc:
Oliver> http://sourceware.org/gdb/onlinedocs/gdb/Pretty-Printing-API.html
Oliver> under display_hint "map"
Ok, I see.
In the 'map' case, each item returned by the 'children' iterator must
still be a 2-tuple of the form (NAME VALUE).
What 'map' means is that the first item fetched from the iterator is
considered to be a key in the map, and the second item fetched from the
iterator is considered to be the corresponding value. Then the 3rd item
is a key again, the 4th is a value again, and so on.
In the CLI the NAME parts are omitted when printing, in this case, just
because it makes the output prettier.
In MI, nothing changes -- the hint is emitted and the MI client is
expected to take whatever action it thinks appropriate.
Here's an abbreviated example from the libstdc++ test suite:
std::map<std::string, int> mp;
mp["zardoz"] = 23;
// { dg-final { note-test mp {std::map with 1 elements = {["zardoz"] = 23}} } }
That last line means that 'print mp' here should show:
std::map with 1 elements = {["zardoz"] = 23}
If you dig into the libstdc++ StdMapPrinter code you see:
def next(self):
if self.count % 2 == 0:
n = self.rbiter.next()
n = n.cast(self.type).dereference()['_M_value_field']
self.pair = n
item = n['first']
else:
item = self.pair['second']
result = ('[%d]' % self.count, item)
self.count = self.count + 1
return result
So in the example above it returns a list like
[ ('[0]', '"zardoz"'), ('[1]', 23) ]
My question for you is: how can we improve the documentation to make
this more clear?
Right now they read:
@item map
Indicate that the object being printed is ``map-like'', and that the
children of this value can be assumed to alternate between keys and
values.
Tom