Re: Problem installing PyEpics

[Matt Newville <newville@cars.uchicago.edu>]

Hi Andrew,

On Mon, Jan 30, 2017 at 4:15 PM, Andrew Johnson <anj@aps.anl.gov> wrote:

Hi Matt,

On 01/30/2017 03:09 PM, Matt Newville wrote:
> A larger-scale question would be:  why do libca.so and libCom.so need to
> be linked against libreadline? I would have thought that readline would
> be something that iocsh needs, but not libca / libCom.

The core of iocsh is a part of libCom.

It is possible to build Base with readline disabled, but on Linux that
configuration is not the default since readline comes with all Linux
distributions. The switch to turn it off is to comment out all of the 3
lines which set COMMANDLINE_LIBRARY in the appropriate file
  configure/os/CONFIG_SITE.Common.<host-arch>
or to set that variable to EPICS. Note that you have to rebuild libCom
for this change to take effect.

- Andrew

--
Arguing for surveillance because you have nothing to hide is no
different than making the claim, "I don't care about freedom of
speech because I have nothing to say." -- Edward Snowdon

Ah, thanks.   I've always assumed that on *nix systems that there will be a libca.so and libCom.so available, and that it can be used by python.  But the increase in popularity of non-system-provided Python distributions such as Anaconda can cause the sort of trouble Allan saw, because that may be using a conflicting dynamic library than the one used to build libca/libCom. In practice, it seems like only readline that causes the trouble.

This may be a good reason to reconsider providing pre-built libca.so and libCom.so for linux and MacOSX, as we do for Windows, at least for Anaconda Python.

--Matt