forked from OSchip/llvm-project
96 lines
4.7 KiB
ReStructuredText
96 lines
4.7 KiB
ReStructuredText
The SB API Coding Rules
|
|
=======================
|
|
|
|
The SB APIs constitute the stable C++ API that lldb presents to external
|
|
clients, and which get processed by SWIG to produce the Python bindings to
|
|
lldb. As such it is important that they not suffer from the binary
|
|
incompatibilities that C++ is so susceptible to. We've established a few rules
|
|
to ensure that this happens.
|
|
|
|
The classes in the SB API's are all called SB<SomeName>, where SomeName is in
|
|
CamelCase starting with an upper case letter. The method names are all
|
|
CamelCase with initial capital letter as well.
|
|
|
|
All the SB API classes are non-virtual, single inheritance classes. They should
|
|
only include SBDefines.h or other SB headers as needed. There should be no
|
|
inlined method implementations in the header files, they should all be in the
|
|
implementation files. And there should be no direct ivar access.
|
|
|
|
You also need to choose the ivars for the class with care, since you can't add
|
|
or remove ivars without breaking binary compatibility. In some cases, the SB
|
|
class is a thin wrapper around an internal lldb_private object. In that case,
|
|
the class can have a single ivar, which is either a pointer, shared_ptr or
|
|
unique_ptr to the object in the lldb_private API. All the lldb_private classes
|
|
that get used this way are declared as opaque classes in lldb_forward.h, which
|
|
is included in SBDefines.h. So if you need an SB class to wrap an lldb_private
|
|
class that isn't in lldb_forward.h, add it there rather than making a direct
|
|
opaque declaration in the SB classes .h file.
|
|
|
|
If the SB Class needs some state of its own, as well as the backing object,
|
|
don't include that as a direct ivar in the SB Class. Instead, make an Impl
|
|
class in the SB's .cpp file, and then make the SB object hold a shared or
|
|
unique pointer to the Impl object. The theory behind this is that if you need
|
|
more state in the SB object, those needs are likely to change over time, and
|
|
this way the Impl class can pick up members without changing the size of the
|
|
object. An example of this is the SBValue class. Please note that you should
|
|
not put this Impl class in the lldb namespace. Failure to do so leads to
|
|
leakage of weak-linked symbols in the SBAPI.
|
|
|
|
In order to fit into the Python API's, we need to be able to default construct
|
|
all the SB objects. Since the ivars of the classes are all pointers of one sort
|
|
or other, this can easily be done, but it means all the methods must be
|
|
prepared to handle their opaque implementation pointer being empty, and doing
|
|
something reasonable. We also always have an "IsValid" method on all the SB
|
|
classes to report whether the object is empty or not.
|
|
|
|
Another piece of the SB API infrastructure is the Python (or other script
|
|
interpreter) customization. SWIG allows you to add property access, iterators
|
|
and documentation to classes, but to do that you have to use a Swig interface
|
|
file in place of the .h file. Those files have a different format than a
|
|
straight C++ header file. These files are called SB<ClassName>.i, and live in
|
|
"scripts/interface". They are constructed by starting with the associated .h
|
|
file, and adding documentation and the Python decorations, etc. We do this in a
|
|
decidedly low-tech way, by maintaining the two files in parallel. That
|
|
simplifies the build process, but it does mean that if you add a method to the
|
|
C++ API's for an SB class, you have to copy the interface to the .i file.
|
|
|
|
API Instrumentation
|
|
-------------------
|
|
|
|
The reproducer infrastructure requires API methods to be instrumented so that
|
|
they can be captured and replayed. Instrumentation consists of two macros,
|
|
``LLDB_REGISTER`` and ``LLDB_RECORD``. Both can be automatically generated with
|
|
the ``lldb-instr`` utility.
|
|
|
|
To add instrumentation for a given file, pass it to the ``lldb-instr`` tool.
|
|
Like other clang-based tools it requires a compilation database
|
|
(``compile_commands.json``) to be present in the current working directory.
|
|
|
|
::
|
|
|
|
./bin/lldb-instr /path/to/lldb/source/API/SBDebugger.cpp
|
|
|
|
|
|
The tool will automatically insert ``LLDB_RECORD`` macros inline, however you
|
|
will need to run ``clang-format`` over the processed file, as the tool
|
|
(intentionally) makes no attempt to get that right.
|
|
|
|
The ``LLDB_REGISTER`` macros are printed to standard out between curly braces.
|
|
You'll have to copy-paste those into the corresponding `RegsiterMethods`
|
|
function in the implementation file. This function is fully specialized in the
|
|
corresponding type.
|
|
|
|
::
|
|
|
|
template <> void RegisterMethods<SBDebugger>(Registry &R) {
|
|
...
|
|
}
|
|
|
|
|
|
When adding a new class, you'll also have to add a call to ``RegisterMethods``
|
|
in the ``SBRegistry`` constructor.
|
|
|
|
The tool can be used incrementally. However, it will ignore existing macros
|
|
even if their signature is wrong. It will only generate a ``LLDB_REGISTER`` if
|
|
it emitted a corresponding ``LLDB_RECORD`` macro.
|