Experimental Physics and
Industrial Control System

Andrew Johnson via Core-talk <core-talk at aps.anl.gov> · Thu, 06 Oct 2022 17:13:18 -0000

The original change (released 7½ years ago) was to properly support
32-bit raw values as you requested in https://epics.anl.gov/tech-
talk/2013/msg00684.php but without triggering UB, which modern compiler
optimizers love to rely on to break previously-working-but-non-portable
code.

ROFF can't hold negative values, it was designed to support ADCs and
DACs with an offset zero. If you have device support that was setting a
negative ROFF it was depending on overflowing a uint32 calculation,
which gcc allows with the -fwrapv flag but EPICS doesn't set that and it
isn't portable.

I don't think we can change this in the record types at all, the device
support has to provide any fixes necessary IMHO.

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https://bugs.launchpad.net/bugs/1991765

Title:
  Problem with ROFF change in ai/ao

Status in EPICS Base:
  New

Bug description:
  In commit ffcbd4ca, ROFF of ai and ao have been changed from LONG to ULONG.
  This has caused problems when migrating from EPICS 3.14 to 7.0 in multiple cases where ROFF was negative and thus became a huge positive value.
  There seems to be no workaround for this regression.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System