[lldb-dev] LLDB plugin dylib

[Joe Ranieri]

On Thu, Sep 26, 2013 at 1:05 PM, Greg Clayton <gclayton at apple.com> wrote:
> Currently they have to be built in because the internals of lldb (anything inside the "lldb_private" namespace) can change at anytime.
>
> In order to allow external plug-ins, we would need to make sure to make sure the API doesn't get violated. There are some important rules in place right now since we are vending a C++ API:
> 1 - No virtual functions in any public classes (lldb::SB*)
> 2 - No inheritance
> 3 - One member which is an opaque pointer that never changes size (shared pointer, weak pointer, auto_ptr/unique_ptr, or just a pointer if the object never gets destroyed).
>
> This allows people to link against the C++ classes and maintains a stable C++ API.
>
> The problem with making plug-ins that only use the public interface, is it is challenging to abide by these rules. I am sure we can do it, we just haven't done it yet. For some plug-ins like disassemblers, it would be easier than others, like subclassing a new process plug-in or a new symbol file parser since these are create many lldb_private classes.
>
> Greg

Given the lack of a stable C++ API across shared library boundaries on
some platforms, would it make sense to expose a C API? It seems like
the external plugin's main function could register a struct of
function pointers for each internal plugin type (disassembler,
platform, etc). Internally there'd be subclasses of the lldb_private
classes for the corresponding plugin type that call through to the
appropriate function pointer registered by the external plugin. I
think this is more or less what the OperatingSystemPython class
already does.

The catch is figuring out how stable the C API would be and how much
it would impede the ability to move the rest of the codebase forward.

-- Joe Ranieri