Experimental Physics and
Industrial Control System

mdavidsaver via Core-talk <[email protected]> · Thu, 16 May 2019 21:57:42 -0000

It looks like we missed the init() function, which seems like it should
be "long (*init)(void);".  Can we fix w/o a compatibility break?

> struct typed_rset {
>     long number; /* number of support routines */
>     long (*report)(void *precord);
>     long (*init)();

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https://bugs.launchpad.net/bugs/1666924

Title:
  remove all uses of XXXSUPFUN typedefs

Status in EPICS Base:
  Fix Released

Bug description:
  The OO-like function tables defined in recSup.h, devSup.h, and
  drvSup.h disable type checking by using the typedefs RECSUPFUN,
  DEVSUPFUN, and DRVSUPFUN, respectively, which declare the methods as
  having "any number and type of arguments". For instance, this is in
  devSup.h:

  typedef long (*DRVSUPFUN) ();   /* ptr to driver support function*/

  typedef struct drvet {	/* driver entry table */
  	long		number;		/*number of support routines*/
  	DRVSUPFUN	report;		/*print report*/
  	DRVSUPFUN	init;		/*init support*/
  }drvet;

  Supports have to uses casts to XXXSUPFUN when they fill a xxxet
  structure.

  I think listing the well-known reasons why this is bad would be
  redundant. As an illustration, see the bug recently uncovered by
  Carsten Winkler (http://www.aps.anl.gov/epics/tech-
  talk/2017/msg00347.php).

  I propose to change the definition of these structs so that all the
  methods get their proper type.

  There remains the question how to handle the (implicit) subtype
  polymorphism for things like dbCommon. I propose to handle this by
  forcing support definitions to explicitly cast the argument (e.g.
  dbCommon *precord) to the appropriate subtype; this adds one line of
  code to each support function e.g.

  long process(dbCommon *pdbCommon)
  {
      aoRecord *prec = (aoRecord *)pdbCommon;
      ...use prec from here onward...
  }

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System