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 `print`ing 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:
> 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:
> 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, I don't current know of a motivating reason forhowever for typical lldb usage, I can't think of a
typical lldb usagemotivating reason to do so. As it stands, the only thing the docs say to do, that thisthe 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.