Experimental Physics and
Industrial Control System

Eric Norum <[email protected]> · Fri, 18 Feb 2005 16:02:38 -0600

On Feb 18, 2005, at 3:36 PM, Eric Norum wrote:


EPICS plays fast and loose with casts. Modern compilers use the new
aliasing rules to enable some optimizations that would have been
impossible otherwise.
Given the way that these pointers are used in EPICS I believe that no
problem actually exists. Unfortunately, I don't see an easy way to
work around the problem since EPICS allows a 'dset' to contain
different numbers of function pointers. Sloppy design (there probably
should have been a 'dsetCommon' at the beginning of each different
flavour of 'dset' structure), but hard to fix now.

Andrew Johnson points out that the warnings can be eliminated simply by
passing the cast through a (char *) cast first:

diff -u -r1.1.2.3 epicsExport.h

--- libCom/misc/epicsExport.h   30 Mar 2004 21:56:23 -0000      1.1.2.3
+++ libCom/misc/epicsExport.h   18 Feb 2005 21:59:45 -0000
@@ -26,7 +26,7 @@
 #define epicsExportAddress(typ,obj) \
 epicsShareExtern typ *EPICS_EXPORT_POBJ(typ,obj); \
-epicsShareDef typ *EPICS_EXPORT_POBJ(typ,obj) = (typ *)&obj
+epicsShareDef typ *EPICS_EXPORT_POBJ(typ,obj) = (typ *)(char *)&obj
 #define epicsExportRegistrar(func) \

epicsShareFunc REGISTRAR EPICS_EXPORT_PFUNC(func) =
(REGISTRAR)(void*)&func

I will commit this change to the R3_14_2 branch and to the main trunk.
--

Eric Norum <[email protected]>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System