Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Mon, 18 Apr 2011 15:42:12 -0500

Hi Ben,

On Monday 18 April 2011 14:24:12 J. Lewis Muir wrote:
> FYI, there were a few warnings when building seq 2.0.13-rc1.

This section of Lewis' output is illuminating:

>preprocessing ../tooLong.st
>/opt/vxworks-tornado-2.0.2/host/x86-linux/bin/ccppc -x c -E -DCPU=PPC603
> -DvxWorks -I. -I../O.Common -I. -I.. -I../../../include/os/vxWorks
> -I../../../include -I/home/jlmuir/tmp/opt/epics-3.14.11/include/os/vxWorks
> -I/home/jlmuir/tmp/opt/epics-3.14.11/include     
> -I/opt/vxworks-tornado-2.0.2/target/h ../tooLong.st > tooLong.i
>converting tooLong.i
>../../../bin/linux-x86_64/snc    tooLong.i -o tooLong.c.tmp
>line 17: cannot assign variable >l< because on this architecture its (base)
> type is larger than 4 bytes. Such variables cannot be faithfully mapped to
> any of the Channel Access base types. Try declaring the variable as 'int'
> or, if that is still too large on your system, as 'short'.
>line 20: cannot assign variable >ul< because on this architecture its (base)
> type is larger than 4 bytes. Such variables cannot be faithfully mapped to
> any of the Channel Access base types. Try declaring the variable as 'int'
> or, if that is still too large on your system, as 'short'.

Unfortunately those warnings from snc are wrong, since this is a cross-build 
for the vxWorks-ppc603 architecture where long is 32 bits so is legal.  Since 
snc doesn't know what architecture the target will be compiled for or what the 
characteristics of that target are, I think it has to defer those size checks 
to the C compiler when someone uses a long variable.  It can do that by 
generating code like this:

#include <limits.h>
#if LONG_MAX > 2147483647L
#  error Cannot assign ...
#endif

C doesn't allow the use of sizeof in a #if condition, but using LONG_MAX like 
this works fine.

Thanks,

- Andrew
-- 
An error is only a mistake if you don't learn from it.
When you learn something from it, it becomes a lesson.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System