Re: Automatically generate iocsh registrar code?

[Andrew Johnson <anj@aps.anl.gov>]

Benjamin Franksen wrote:
> On Friday 08 June 2007 18:19, Carl Lionberger wrote:
> > Here's a perl script
> >
> > Susanna Jacobson wrote:
> > > Does anyone have a script or program that will take a set of C
> > > function declarations and generate the C code to register those
> > > functions with the iocsh?
> > >
> > > I have 18 functions to register, some with 4 or 5 arguments.
>
> What about integrating this into the EPICS build system? Would be quite 
> convenient and could reduce the likelyhood of errors, e.g. when the type of 
> a registered routine changes.

I haven't tried Carl's script but it seems like an excellent way to do 
the boring task of generating the appropriate C code from the command 
functions, and is great for doing this in a one-off manner.  However I 
do think that any final automated solution that goes into Base should 
not require us to include code that parses C declarations - it's much 
easier to generate a declaration than it is to reliably parse one.

I have wanted to incorporate something that generates the registration 
code into the DBD file syntax ever since we added iocsh, but haven't yet 
worked out what is the best way to do so - just adding the first thing 
that someone gets to work is unfortunately a recipe for future headaches 
in maintenance and upgrades, thus careful consideration is needed.

My current thoughts are that the DBD file might be used to generate a C 
header file which declares the command functions (similar to how we do 
record types in the current code-base).  This header would then be 
included by the C file that defines those functions, thus the C compiler 
would do the work of ensuring that the routine implemented actually 
matches the command that will call it.

Note that the command information in the DBD file will also be useful 
for future versions of the IRMIS parser for st.cmd scripts, so it can 
use a device support's hardware configuration commands to map installed 
components to record addresses.  I have been working on replacing the 
current DBD file parser infrastructure (dbStaticLib, written in C) with 
a Perl implementation in the R3.15 tree, which will be much easier to 
modify and extend to do things like this.

- Andrew
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