Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 15 Nov 2013 18:42:48 -0600

Hi Garth,

There have been some significant modifications made to the version of

msi which is found in Base 3.15. I'm not sure if they will completely

solve your problem, but you might want to check the documentation at

http://www.aps.anl.gov/epics/base/R3-15/0-docs/msi.html which shows the

new global syntax in the substitutions file. There are more docs

including an EBNF grammar in the Application Developers Guide at

http://www.aps.anl.gov/epics/base/R3-15/0-docs/AppDevGuide/node7.html#SECTION007220000000000000000

-- the same syntax works in both msi and dbLoadTemplate(). If you want

to try out the new msi it should be possible to extract just the

src/ioc/dbtemplate/msi.c file and build it against a 3.14.12 version of

Base.

You can also of course use any templating language you like to write

substitutions. We provide msi which shares the dbLoadTemplate syntax,

but other sites have written their own tools when they had specific

needs which msi can't meet. You could modify msi as well, but I would

suggest starting from the 3.15 version if you think you might want to

offer your changes back to us.

HTH,

- Andrew

On 11/15/2013 06:15 PM, Brown, Garth wrote:

I'll add a few tangentially related thoughts on how msi/macLib might
be modified. It would be nice if there was a way to keep a macro with
a default value in a template unexpanded. That is, if sample.template
contains the line
        field(X, "$(MYX=3)" )
then sample.substitutions could have a way to indicate that MYX
shouldn't be expanded and should retain the default value part, so
that sample.db still had exactly that line. As it is, you can leave
MYX undefined, which expands to
        field(X, "3" )
Or you can have in the substitutions { MYX='$(MYX)' }, which expands
to
        field(X, "$(MYX)" )    # default value is lost
The macro with default can't survive msi unchanged.
If there were a way to leave the macro undefined with the default
value intact, I could solve my problem with two levels of
substitutions files: a general substitutions file that contained
macros with defaults for everywhere, and environment specific
substitutions files  that used the output of the general one as a
template.
Getting more technical about how that might work, you could interpret
{ MYX=$(MYX) } recursive definition as not wanting the macro
substituted, rather than as an error condition. Right now, macLib
will turn this into $(MYX, recursive), indicating an error and losing
the default value.
I had a look in macCore.c where this case is handled, and didn't
immediately see how to implement that. The recursive definition is
detected one call stack level below where the default value is
specified.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System