Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <[email protected]> · Mon, 1 Apr 2019 12:55:28 -0700

Hi Lewis,

You're right about the example.  Would you like to submit a correction?
(via launchpad, github, or email a patch)

https://github.com/epics-base/epics-base/blob/3.15/documentation/RELEASE_NOTES.html

What I've done before is equivalent to:

>   #ifndef VERSION_INT
>   #  define VERSION_INT(V,R,M,P) ( ((V)<<24) | ((R)<<16) | ((M)<<8) | (P))
>   #  define EPICS_VERSION_INT  VERSION_INT(EPICS_VERSION, EPICS_REVISION, EPICS_MODIFICATION, EPICS_PATCH_LEVEL)
>   #endif
>   #if EPICS_VERSION_INT < VERSION_INT(3,15,0,0)
>   #  error EPICS Base R3.15.0 or later is required
>   #endif

On 4/1/19 12:35 PM, J. Lewis Muir via Tech-talk wrote:
> Hello, all.
> 
> At
> 
>   https://epics.anl.gov/base/R3-15/6-docs/RELEASE_NOTES.html
> 
> under
> 
>   Changes made between 3.14.x and 3.15.0.1
> 
> in the
> 
>   Changes to epicsVersion.h
> 
> section, it says
> 
>   A new pair of macros has been added to make version number comparisons
>   easier. Code that will not work with a version of Base before 3.15.0
>   can now be written like this to prevent it from compiling:
> 
>   #if defined(VERSION_INT) && EPICS_VERSION_INT < VERSION_INT(3,15,0,0)
>   #  error EPICS Base R3.15.0 or later is required
>   #endif
> 
> That has two problems, at least on macOS Mojave with Clang 10.0.1:
> 
> 1. The function-like macro VERSION_INT can't portably be used later on
>    in the same expression as the check for whether it's defined when
>    it's not defined.
> 
>    For example, when compiling foo.c with the above preprocessor snippet
>    against EPICS Base 3.14.12.8, Clang errors out with:
> 
>      ../foo.c:37:49: error: function-like macro 'VERSION_INT' is not defined
>      #if defined(VERSION_INT) && EPICS_VERSION_INT < VERSION_INT(3,15,0,0)
>                                                      ^
>      1 error generated.
> 
>    A portable fix would be to check whether VERSION_INT is defined on
>    its own:
> 
>      #if defined(VERSION_INT)
>      #  if EPICS_VERSION_INT < VERSION_INT(3,15,0,0)
>      #    error EPICS Base R3.15.0 or later is required
>      #  endif
>      #endif
> 
> 2. The logic of the macro snippet is wrong.  For example, when compiling
>    against EPICS Base 3.14.x, the error (i.e., "EPICS Base R3.15.0
>    or later is required") is *not* generated.  This is because the
>    VERSION_INT function-like macro is not defined in EPICS Base 3.14.x.
> 
> Regards,
> 
> Lewis
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System