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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 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 <some expression>]` 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.
Note the point that when implementing only `__repr__` (and not `__str__`), then
`__repr__` is used when `str()` is called.
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 for
typical lldb usage. As it stands, the only thing 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.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D127458
Files:
lldb/bindings/macros.swig
Index: lldb/bindings/macros.swig
===================================================================
--- lldb/bindings/macros.swig
+++ lldb/bindings/macros.swig
@@ -1,6 +1,6 @@
%define STRING_EXTENSION_LEVEL(Class, Level)
%extend {
- std::string lldb:: ## Class ## ::__str__(){
+ std::string lldb:: ## Class ## ::__repr__(){
lldb::SBStream stream;
$self->GetDescription (stream, Level);
const char *desc = stream.GetData();
@@ -15,7 +15,7 @@
%define STRING_EXTENSION(Class)
%extend {
- std::string lldb:: ## Class ## ::__str__(){
+ std::string lldb:: ## Class ## ::__repr__(){
lldb::SBStream stream;
$self->GetDescription (stream);
const char *desc = stream.GetData();
Index: lldb/bindings/macros.swig
===================================================================
--- lldb/bindings/macros.swig
+++ lldb/bindings/macros.swig
@@ -1,6 +1,6 @@
%define STRING_EXTENSION_LEVEL(Class, Level)
%extend {
- std::string lldb:: ## Class ## ::__str__(){
+ std::string lldb:: ## Class ## ::__repr__(){
lldb::SBStream stream;
$self->GetDescription (stream, Level);
const char *desc = stream.GetData();
@@ -15,7 +15,7 @@
%define STRING_EXTENSION(Class)
%extend {
- std::string lldb:: ## Class ## ::__str__(){
+ std::string lldb:: ## Class ## ::__repr__(){
lldb::SBStream stream;
$self->GetDescription (stream);
const char *desc = stream.GetData();
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