[fpc-pascal] Re: Fix & Continue in FPC [was: off-topic discussion)

[Lukasz Sokol]

On 28/02/2012 10:45, Jonas Maebe wrote:
> 
> On 27 Feb 2012, at 13:32, Lukasz Sokol wrote:
> 
>> On 26/02/2012 11:17, Mattias Gaertner wrote:
>>> The next step is to "compile" the function on every change. Easy
>>> with an interpreter. How to compile only one function of a big
>>> program and insert/replace it?
>> 
>> Sorry for a plug, but MS VC++ 6.0 (!)* allowed for Pause->Edit
>> Code-> Quick compile->Resume Execution kind of workflow...
>> 
>> Yes, in Debug/Pause mode, you COULD write a {code block} and then
>> go Debug->Apply and Continue (or something like that) and voila, 
>> you could totally change code paths ... (Not that I know much about
>> internals/constraints of this, to be honest, but of all, i found
>> that a very cool feature)
>> 
>> Is there a way to add THAT to FPC/Lazarus/GDB world ?
> 
> Apple supported that in older versions of their development tools,
> and it worked as well (or as badly) with FPC as it did with GCC. It
> required changes to their dynamic linker (for the code replacement)
> and to GDB. It was extremely flakey and limited though, and they
> abandoned it fairly quickly.
> 
> Since the required support is generally not part of the compiler but
> of the environment (you need a way to inject the new code, and
> possibly data, into the process, and link up everything with the new
> version), I don't think this is something that can be added as an
> "FPC" feature.
> 
> 
> Jonas 

(Un)fortunately I don't know much about the internals, as I mentioned :)

The closest idea that looks similar is a loadable library: you can unload a dll 
(or a .so), edit/recompile/rebuild it while the caller program is paused/waiting,
then reload it (with an obvious constraint that you can't modify the interfaces
that the already-running program knows)
 - now imagine each code/data block is separate 'object' that can be loaded/unloaded...?

(Did I just hit on the unmentionable feature of loadable modules :) )

Lukasz