When using the script Python repl, SB objects are printed in a way that gives
the user no information. The simplest example is:
(lldb) script lldb.debugger <lldb.SBDebugger; proxy of <Swig Object of type 'lldb::SBDebugger *' at 0x1097a5de0> >
This output comes from the Python repl printing the repr() of an object.
None of the SB classes implement __repr__, and all print like the above.
However, many (most?, all?) SB classes implement __str__. Because they
implement __str__, a more detailed output can be had by printing the
object, for example:
(lldb) script print(lldb.debugger) Debugger (instance: "debugger_1", id: 1)
For convenience, this change switches all SB classes that implement to
__str__ to instead implement __repr__. The result is that str() and
repr() will produce the same output. This is because str calls __repr__
for classes that have no __str__ method.
The benefit being that when writing a script invocation, you don't need to
remember to wrap in print(). If that isn't enough motivation, consider the
case where your Python expression results in a list of SB objects, in that case
you'd have to map or use a list comprehension like [str(x) for x in <expr>]
in order to see the details of the objects in the list.
For reference, the docs for repr say:
repr(object)Return a string containing a printable representation of an object. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval(); otherwise, the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a __repr__() method.
and the docs for __repr__ say:
object.repr(self)Called by the repr() built-in function to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment). If this is not possible, a string of the form <...some useful description...> should be returned. The return value must be a string object. If a class defines __repr__() but not __str__(), then __repr__() is also used when an “informal” string representation of instances of that class is required. This is typically used for debugging, so it is important that the representation is information-rich and unambiguous.
Even if it were convenient to construct Python expressions for SB classes so
that they could be eval'd, however for typical lldb usage, I can't think of a
motivating reason to do so. As it stands, the only action the docs say to do,
that this change doesn't do, is wrap the repr string in <> angle brackets.
An alternative implementation is to change lldb's python repl to apply str()
to the top level result. While this would work well in the case of a single SB
object, it doesn't work for a list of SB objects, since str([x]) uses repr
to convert each list element to a string.